Diaz et al 2003 Water resources data Puerto Rico and the US Virgin Islands water year 2003

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Date: 2003
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U.S. Department of the Interior U.S. Geological Survey Water Resources Data Puerto Rico and the U.S. Virgin Islands Water Year 2003 By Pedro L. Díaz, Zaida Aquino, Carlos Figueroa-Alamo, René García, and Ana V. Sánchez Water-Data Report PR-03-1 Prepared in cooperation with the Commonwealth of Puerto Rico, the Government of the U.S. Virgin Islands, and with other agencies 2005 U.S. Department of the Interior Gale A. Norton, Secretary U.S. Geological Survey Charles G. Groat, Director U.S. Geological Survey GSA Center, Suite 400-15 651 Federal Drive Guaynabo, PR 00965 Telephone: (787) 749-4346 Information about the USGS, Caribbean District is available on the Internet at http://pr.water.usgs.gov/ Information about all USGS reports and products is available by calling 1-888-ASK-USGS or on the Internet via the World Wide Web at http://www.usgs.gov/ Additional earth science information is available by accessing the USGS home page at http://www.usgs.gov/ iii PREFACE This annual hydrologic data report of Puerto Rico and the U.S. Virgin Islands is one of a series of annual reports that document hydrologic data gathered from the U.S. Geological Survey's surface- and ground-water data-collection networks in each state, Puerto Rico, the U.S. Virgin Islands, and the other Trust Territories. These records of streamflow, ground-water levels, and quality-of-water provide the hydrologic information needed by state, local, and Federal agencies, and the private sector for developing and managing our Nation's land and water resources. The report is the culmination of a concerted effort by dedicated personnel of the U.S. Geological Survey, Water Resources Division, who collected, compiled, analyzed, verified, and organized the data, and who typed, edited, and assembled the report. In addition to the authors, who had primary responsibility for assuring that the information contained herein is accurate, complete, and adheres to the U.S. Geological Survey policy and established guidelines, the following personnel contributed significantly to the collection, processing, and tabulations of the data: José M. Agis Ronald T. Richards Alexander Avila Gilberto Rodríguez George Arroyo Manuel Rosario Iris M. Concepción José René Sánchez Israel Cruz Luis Santiago-Rivera Angel G. Ferrer Carlos Santos Senén Guzmán-Ríos Luis Soler Felipe Hernández Elliot M. Sosa Yaniré Martínez Angel Torres José Merced Heriberto Torres-Sierra Carlos Narvaez James Torres Julio Oms Sigfredo Torres-González Awilda Ortíz Ahmed Valencia Rafael Peña-Cortéz Luis Vega Francisco Maldonado prepared the illustrations and Ruth I. Guzmán typed the text of the report and was mainly responsible for the assemble of the book using Automated Annual Report (AAR) Scripts for Surface-Water Discharge and Water-Quality Stations. This report was prepared in cooperation with agencies of the Commonwealth of Puerto Rico, the Government of the U.S. Virgin Islands, and with other Federal agencies under the general supervision of Pedro L. Díaz, Caribbean District Chief, San Juan, Puerto Rico. REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS 6. AUTHOR(S) 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. AGENCY REPORT NUMBER 11. SUPPLEMENTARY NOTES 12a. DISTRIBUTION / AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE 13. ABSTRACT (Maximum 200 words) 14. SUBJECT TERMS 15. NUMBER OF PAGES 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT 18. SECURITY CLASSIFICATION OF THIS PAGE 19. SECURITY CLASSIFICATION OF ABSTRACT 20. LIMITATION OF ABSTRACT 1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED SPONSORING / MONITORING Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for r eviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding t his burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (07 04-0188), Washington, DC 20503. April 2005 Annual - October 1, 2002 to September 30, 2003 Water Resources Data for Puerto Rico and the U.S. Virgin Islands Water Year 2003 Pedro L. Díaz, Zaida Aquino, Carlos Figueroa-Alamo, René García, Ana V. Sánchez U.S. Geological Survey, Water Resources Division GSA Center, 651 Federal Drive, Suite 400-15 Guaynabo, Puerto Rico 00965 USGS-WDR-PR-03-1 U.S. Geological Survey, Water Resources Division GSA Center, 651 Federal Drive, Suite 400-15 Guaynabo, Puerto Rico 00965 USGS-WDR-PR-03-1 Prepared in cooperation with the Commonwealth of Puerto Rico, the Government of the U.S. Virgin Islands, and other agencies. NO RESTRICTION ON DISTRIBUTIONS Water resources data for surface-water, quality-of-water, and ground-water records for the 2003 water year for Puerto Rico and the U.S. Virgin Islands consists of records of discharge, water quality of streams, and water levels of wells. This report contains discharge records for 86 streamflow-gaging stations; daily sediment records for 22 streamflow stations; stage records for 17 reservoirs; water-quality records for 17 streamflow-gaging stations, 39 ungaged stream sites, 2 lagoons, and 1 bay; and water- level records for 72 observation wells. These data represent that part of the National Water Data System collected by the U.S. Geological Survey and cooperating local and Federal agencies in Puerto Rico and the U.S. Virgin Islands. *Surface water, *Water quality, *Ground water, Aquifers, Chemical analysis, Gaging stations, Hydrologic data sediments, Streamflow, Water analysis, Water levels, Lakes 584 Unclassified Unclassified NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std 239-18 298-102 v CONTENTS Page Preface........................................................................................................................................................................iii List of surface-water and water-quality stations, in downstream order, for which records are published in this volume ..................................................................................................................................vii List of ground-water wells, by basin, for which records are published in this volume ............................................ xii List of discontinued streamflow stations .................................................................................................................. xv Introduction................................................................................................................................................................. 1 Cooperation................................................................................................................................................................. 2 Summary of hydrologic conditions............................................................................................................................. 3 Precipitation ................................................................................................................................................................ 3 Surface water....................................................................................................................................................... 4 Ground water....................................................................................................................................................... 6 Water quality ....................................................................................................................................................... 9 Special networks and programs ................................................................................................................................ 13 Explanation of records .............................................................................................................................................. 14 Downstream order and station number ..................................................................................................................... 14 Numbering system for wells and miscellaneous sites............................................................................................... 19 Explanation of stage and water discharge records .................................................................................................... 19 Data collection and computation ....................................................................................................................... 19 Data presentation............................................................................................................................................... 20 Station manuscript ...................................................................................................................................... 21 Data table of daily mean values.................................................................................................................. 22 Statistics of monthly mean data.................................................................................................................. 22 Summary statistics...................................................................................................................................... 22 Identifying estimated daily discharge................................................................................................................ 24 Accuracy of field data and computed results .................................................................................................... 24 Other data records available .............................................................................................................................. 25 Records of surface-water quality .............................................................................................................................. 25 Classification of records....................................................................................................................................25 Arrangement of records..................................................................................................................................... 25 On-site measurements and sample collection.................................................................................................... 25 Water temperature ............................................................................................................................................. 26 Sediment............................................................................................................................................................ 26 Laboratory measurements .................................................................................................................................27 Data presentation............................................................................................................................................... 27 Remark codes .................................................................................................................................................... 28 Records of ground-water levels ................................................................................................................................ 28 Data collection and computation ....................................................................................................................... 28 Data presentation............................................................................................................................................... 29 Water-levels tables ............................................................................................................................................29 Access to U.S. Geological Survey Water Data ......................................................................................................... 30 Definition of terms .................................................................................................................................................... 31 Techniques of Water-Resources Investigations of the U.S. Geological Survey ....................................................... 49 Surface- and quality-of-water records for Puerto Rico ............................................................................................. 53 Ground-water records for Puerto Rico.................................................................................................................... 481 Ground-water records for U.S. Virgin Islands ....................................................................................................... 553 Index........................................................................................................................................................................ 561 vi ILLUSTRATIONS Page Figure 1. Graphs showing monthly-mean discharge of selected streams in Puerto Rico.....................................5 2. Graphs showing ground-water levels at selected wells in Puerto Rico and the U.S. Virgin Islands ...........................................................................................................................6 3. Map showing location of maximum concentrations of fecal coliform bacteria at the water-quality sampling sites in Puerto Rico.............................................................................10 4. Map showing location of maximum concentrations of fecal streptococci bacteria at the water-quality sampling sites in Puerto Rico.............................................................................11 5. Map showing location of surface-water stations in Puerto Rico.........................................................15 6. Map showing location of water-quality stations in Puerto Rico .........................................................16 7. Map showing location of ground-water stations in Puerto Rico ........................................................17 8. Map showing location of ground-water stations in the U.S. Virgin Islands .......................................18 9. Grid showing system for numbering wells and miscellaneous sites (latitude and longitude) ............19 10. Map showing the Río Guajataca basin ................................................................................................ 55 11. Map showing the Río Camuy basin .................................................................................................... 65 12. Map showing the Río Grande de Arecibo basin..................................................................................69 13. Map showing the Río Grande de Manatí basin ................................................................................. 161 14. Map showing the Río Cibuco basin .................................................................................................. 193 15. Map showing the Río de la Plata basin .............................................................................................203 16. Map showing the Río Hondo to Río Puerto Nuevo basins................................................................231 17. Map showing the Río Grande de Loíza basin ...................................................................................267 18. Map showing northeastern river basins -- Río Herrera to Río Antón Ruíz basins............................317 19. Map showing southeastern river basins -- Río Humacao to Quebrada Aguas Verdes basins...........349 20. Map showing south coast river basins -- Río Salinas to Río Jacaguas basins...................................377 21. Map showing south coast river basins -- Río Inabón to Río Loco basins .........................................397 22. Map showing the Río Guanajibo basin .............................................................................................441 23. Map showing the Río Yagüez and Río Grande de Añasco basins ....................................................455 24. Map showing the Río Culebrinas basin.............................................................................................469 TABLES Page Table 1. Islandwide monthly rainfall for the water year 2003 and monthly normal rainfall for the 30-year reference period, 1971-2000 .........................................................................................3 2. Highest ground-water level recorded during 2003 water year and previous high ground-water levels at selected wells in Puerto Rico.......................................................................8 3. Lowest ground-water levels recorded during 2003 water year and previous lowest ground-water levels at selected wells in Puerto Rico.......................................................................8 4. Sediment yields at selected sediment stations for water year 2003 ....................................................12 vii SURFACE-WATER AND WATER-QUALITY STATIONS, IN DOWNSTREAM ORDER, FOR WHICH RECORDS ARE PUBLISHED IN THIS VOLUME (Letter after station name designates type of data: (d) discharge, (c) chemical, (b) biological, (s) sediment, (p) pesticide, (e) elevation, gage heights) Station number Page RIO GUAJATACA BASIN Río Guajataca at Lares (c,b). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50010500. . . . . . . . . . . . . . .56 Lago Guajataca at Damsite near Quebradillas (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50010800 . . . . . . . . . . . . . 58 Canal Principal de Diversiones at Lago Guajataca (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . 50011000 . . . . . . . . . . . . . 60 Río Guajataca above mouth near Quebradillas (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50011400 . . . . . . . . . . . . . 62 RIO CAMUY BASIN Río Camuy near Bayaney (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50014800 . . . . . . . . . . . . . 66 RIO GRANDE DE ARECIBO BASIN Lago Garzas near Adjuntas (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50020100 . . . . . . . . . . . . . 70 Río Grande de Arecibo near Adjuntas (d,c,b,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50020500 . . . . . . . . . . . . . 72 Río Pellejas above Central Pellejas (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50021030 . . . . . . . . . . . . . 80 Río Grande de Arecibo above Utuado (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50021700 . . . . . . . . . . . . . 86 Río Viví below Hacienda El Progreso (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50022810 . . . . . . . . . . . . . 92 Río Grande de Arecibo below Utuado (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50024950 . . . . . . . . . . . . . 94 Río Grande de Arecibo near Utuado (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50025000 . . . . . . . . . . . . 100 Río Saliente at Coabey near Jayuya (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50025155 . . . . . . . . . . . . 102 Río Jauca at Paso Palma (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50025850 . . . . . . . . . . . . 107 Río Caonillas at Paso Palma (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50026025 . . . . . . . . . . . . 113 Rio Caonillas above Lago Caonillas near Jayuya (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50026050 . . . . . . . . . . . . 118 Río Caonillas below Lago Caonillas Tunnel (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50026200 . . . . . . . . . . . . 120 Río Yunes at Hwy 140 near Florida (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50026400 . . . . . . . . . . . . 125 Río Limón above Lago Dos Bocas (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50027000 . . . . . . . . . . . . 131 Lago Dos Bocas at Damsite near Utuado (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50027100 . . . . . . . . . . . . 139 Río Grande de Arecibo below Lago Dos Bocas near Florida (c,b) . . . . . . . . . . . . . . . . . . . 50027250 . . . . . . . . . . . . 141 Río Grande de Arecibo near San Pedro (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50027600 . . . . . . . . . . . . 143 Río Tanamá near Utuado (d,c,b,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50028000 . . . . . . . . . . . . 148 Río Tanamá at Charco Hondo (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50028400 . . . . . . . . . . . . 155 Río Grande de Arecibo at Central Cambalache (d,c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50029000 . . . . . . . . . . . . 157 RIO GRANDE DE MANATI BASIN Río Orocovis at Orocovis (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50030460 . . . . . . . . . . . . 162 Río Orocovis near Orocovis (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50030700 . . . . . . . . . . . . 164 Río Grande de Manatí near Morovis (d,c,b,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50031200. . . . . . . . . . . . . .166 Lago El Guineo at Damsite near Villalba (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50032290 . . . . . . . . . . . . 173 Lago de Matrullas at Damsite near Orocovis (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50032590 . . . . . . . . . . . . 175 Río Bauta near Orocovis (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50034000 . . . . . . . . . . . . 177 Río Grande de Manatí at Ciales (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50035000 . . . . . . . . . . . . 179 Río Grande de Manatí at Highway 149 at Ciales (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50035500 . . . . . . . . . . . . 184 Río Cialitos at Highway 649 at Ciales (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50035950 . . . . . . . . . . . . 186 Río Grande de Manatí at Highway 2 near Manatí (d,c,b,p) . . . . . . . . . . . . . . . . . . . . . . . . 50038100 . . . . . . . . . . . . 190 LAGUNA TORTUGUERO BASIN Laguna Tortuguero outlet near Vega Baja (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50038200 . . . . . . . . . . . . 192 RIO CIBUCO BASIN Río Cibuco below Corozal (d,c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50038320 . . . . . . . . . . . . 194 Río Cibuco at Vega Baja (d,c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50039500 . . . . . . . . . . . . 198 viii SURFACE-WATER AND WATER-QUALITY STATIONS, IN DOWNSTREAM ORDER, FOR WHICH RECORDS ARE PUBLISHED IN THIS VOLUME--Continued Station number Page RIO DE LA PLATA BASIN Lago Carite at Gate Tower near Cayey (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50039990 . . . . . . . . . . . . 204 Río de la Plata at Proyecto La Plata (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50043000 . . . . . . . . . . . . 206 Río de la Plata at Comerío (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50043800 . . . . . . . . . . . . 208 Río de la Plata near Comerio (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50044000 . . . . . . . . . . . . 214 Río Guadiana near Guadiana (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50044810 . . . . . . . . . . . . 216 Río Guadiana near Naranjito (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50044850 . . . . . . . . . . . . 221 Lago La Plata at Damsite near Toa Alta (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50045000 . . . . . . . . . . . . 223 Río de la Plata below La Plata Dam (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50045010 . . . . . . . . . . . . 225 Río de la Plata at Highway 2 near Toa Alta (d,c,b,p) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50046000 . . . . . . . . . . . . 227 Río Hondo at Flood Channel near Cataño (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50047530 . . . . . . . . . . . . 232 RIO DE BAYAMON BASIN Río de Bayamón at Arenas (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50047535 . . . . . . . . . . . . 234 Lago de Cidra at Damsite near Cidra (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50047550 . . . . . . . . . . . . 236 Río de Bayamón below Lago Cidra (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50047560 . . . . . . . . . . . . 238 Río de Bayamón near Aguas Buenas (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50047600 . . . . . . . . . . . . 240 Río de Bayamón near Bayamón (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50047850 . . . . . . . . . . . . 242 Río Guaynabo near Bayamón (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50047990 . . . . . . . . . . . . 244 Río de Bayamón at Flood Channel at Bayamón (c,b,p) . . . . . . . . . . . . . . . . . . . . . . . . . . . 50048510 . . . . . . . . . . . . 246 RIO PUERTO NUEVO BASIN Río Piedras: Lago Las Curías at Damsite near Río Piedras (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50048680 . . . . . . . . . . . . 248 Quebrada Las Curías below Las Curias Dam (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50048690 . . . . . . . . . . . . 250 Río Piedras at El Señorial (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50048770 . . . . . . . . . . . . 252 Río Piedras near Río Piedras (c,b,p) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50048800. . . . . . . . . . . . . .258 Río Piedras at Hato Rey (d,c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50049100 . . . . . . . . . . . . 260 Laguna San José: Laguna San José No. 2 at San Juan (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50049820. . . . . . . . . . . . . .264 Bahía de San Juan: Bahía de San Juan No. 5 at San Juan (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50049920. . . . . . . . . . . . . .265 QUEBRADA BLASINA BASIN Quebrada Blasina near Carolina (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50050300 . . . . . . . . . . . . 268 RIO GRANDE DE LOIZA BASIN Río Grande de Loíza at Quebrada Arenas (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50050900 . . . . . . . . . . . . 270 Quebrada Salvatierra near San Lorenzo (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50051180 . . . . . . . . . . . . 272 Río Cayaguas at Cerro Gordo (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50051310 . . . . . . . . . . . . 274 Río Grande de Loíza at Highway 183 near San Lorenzo (d) . . . . . . . . . . . . . . . . . . . . . . . 50051800 . . . . . . . . . . . . 276 Río Turabo above Borinquén (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50053025 . . . . . . . . . . . . 278 Río Grande de Loíza at Caguas (d,c,b,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50055000 . . . . . . . . . . . . 280 Río Cagüitas: Río Cagüitas near Aguas Buenas (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50055100 . . . . . . . . . . . . 288 Río Cagüitas at Villa Blanca at Caguas (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50055225 . . . . . . . . . . . . 290 Río Cagüitas at Highway 30 at Caguas (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50055250 . . . . . . . . . . . . 292 Río Gurabo: Río Gurabo below El Mangó (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50055750 . . . . . . . . . . . . 296 Río Valenciano near Juncos (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50056400 . . . . . . . . . . . . 298 Río Gurabo at Gurabo (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50057000 . . . . . . . . . . . . 300 Río Gurabo near Gurabo (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50057025 . . . . . . . . . . . . 302 Río Cañas at Río Cañas (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50058350 . . . . . . . . . . . . 304 ix SURFACE-WATER AND WATER-QUALITY STATIONS, IN DOWNSTREAM ORDER, FOR WHICH RECORDS ARE PUBLISHED IN THIS VOLUME--Continued Station number Page RIO GRANDE DE LOIZA BASIN—Continued Lago Loíza at Damsite near Trujillo Alto (c,b,e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50059000 . . . . . . . . . . . . 306 Río Grande de Loíza below Damsite (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50059050 . . . . . . . . . . . . 309 Río Grande de Loíza below Trujillo Alto (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50059100 . . . . . . . . . . . . 311 Río Canóvanas near Campo Rico (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50061800 . . . . . . . . . . . . 313 RIO ESPIRITU SANTO BASIN Quebrada Sonadora near El Verde (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50063440 . . . . . . . . . . . . 315 Río Espíritu Santo near Río Grande (d,c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50063800 . . . . . . . . . . . . 318 Río Grande near El Verde (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50064200 . . . . . . . . . . . . 322 RIO MAMEYES BASIN Río Mameyes near Sabana (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50065500 . . . . . . . . . . . . 324 Río Mameyes at Mameyes (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50066000 . . . . . . . . . . . . 329 RIO SABANA BASIN Río Sabana at Sabana (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50067000 . . . . . . . . . . . . 331 RIO FAJARDO BASIN Río Fajardo near Fajardo (d,c,b,p,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50071000 . . . . . . . . . . . . 333 RIO BLANCO BASIN Quebrada Guabá near Naguabo (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50074950 . . . . . . . . . . . . 342 Río Icacos near Naguabo (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50075000 . . . . . . . . . . . . 344 Río Blanco near Florida (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50076000 . . . . . . . . . . . . 346 RIO HUMACAO BASIN Río Humacao at Las Piedras (d). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50081000. . . . . . . . . . . . . .350 Río Humacao at Highway 3 at Humacao (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50082000 . . . . . . . . . . . . 352 RIO GUAYANES BASIN Río Guayanés at Yabucoa (c,b,p) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50083500 . . . . . . . . . . . . 354 Río Guayanés above mouth at Playa de Guayanés (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . 50086500 . . . . . . . . . . . . 356 RIO MAUNABO BASIN Río Maunabo at Lizas (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50090500 . . . . . . . . . . . . 358 Río Maunabo at Maunabo (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50091000 . . . . . . . . . . . . 360 RIO CHICO BASIN Río Chico at Providencia (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50091800 . . . . . . . . . . . . 362 RIO GRANDE DE PATILLAS BASIN Río Grande de Patillas near Patillas (d,c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50092000 . . . . . . . . . . . . 364 Río Marín near Patillas (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50093000 . . . . . . . . . . . . 368 Lago Patillas at Damsite near Patillas (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50093045 . . . . . . . . . . . . 370 Canal de Riego de Patillas above Guayama Filtration Plant (d) . . . . . . . . . . . . . . . . . . . . . 50093075 . . . . . . . . . . . . 372 Canal de Riego de Patillas below Guayama Filtration Plant (d) . . . . . . . . . . . . . . . . . . . . . 50093078 . . . . . . . . . . . . 374 RIO SALINAS BASIN Río Lapa near Rabo del Buey (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50100200 . . . . . . . . . . . . 378 Río Majada at La Plena (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50100450 . . . . . . . . . . . . 380 RIO COAMO BASIN Río Coamo at Hwy 14 at Coamo (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50106100 . . . . . . . . . . . . 382 Río Coamo near Coamo (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50106500 . . . . . . . . . . . . 384 x SURFACE-WATER AND WATER-QUALITY STATIONS, IN DOWNSTREAM ORDER, FOR WHICH RECORDS ARE PUBLISHED IN THIS VOLUME--Continued Station number Page RIO DESCALABRADO BASIN Río Descalabrado near Los Llanos (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50108000 . . . . . . . . . . . . 386 RIO JACAGUAS BASIN Río Toa Vaca above Lago Toa Vaca (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50110900 . . . . . . . . . . . . 388 Lago Toa Vaca at Damsite near Villalba (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50111210 . . . . . . . . . . . . 390 Lago Guayabal at Damsite near Juana Díaz (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50111300 . . . . . . . . . . . . 392 Río Jacaguas at Juana Díaz (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50111500 . . . . . . . . . . . . 394 RIO INABON BASIN Río Inabón at Real Abajo (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50112500 . . . . . . . . . . . . 398 RIO BUCANA BASIN Río Cerrillos above Lago Cerrillos near Ponce (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50113800 . . . . . . . . . . . . 400 Lago Cerrillos at Damsite near Ponce (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50113950 . . . . . . . . . . . . 402 Río Cerrillos near Ponce (d,c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50114000 . . . . . . . . . . . . 404 RIO PORTUGUES BASIN Río Portugues at Tibes (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50114900 . . . . . . . . . . . . 408 Río Portugués near Ponce (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50115000 . . . . . . . . . . . . 410 Río Portugués at Highway 14 at Ponce (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50115900 . . . . . . . . . . . . 412 Río Portugués at Ponce (c,b,p) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50116200 . . . . . . . . . . . . 414 RIO GUAYANILLA BASIN Río Guayanilla near Guayanilla (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50124200 . . . . . . . . . . . . 416 Río Guayanilla at Central Rufina (c,b,p) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50124700 . . . . . . . . . . . . 418 RIO YAUCO BASIN Lago Lucchetti at Damsite near Yauco (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50125780 . . . . . . . . . . . . 420 Río Yauco above Diversion Monserrate near Yauco (d) . . . . . . . . . . . . . . . . . . . . . . . . . . 50126150 . . . . . . . . . . . . 422 RIO LOCO BASIN Lago Loco at Damsite near Yauco (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50128900 . . . . . . . . . . . . 424 Canal de Riego de Lajas below Lago Loco Dam at Yauco (d) . . . . . . . . . . . . . . . . . . . . . . 50128905 . . . . . . . . . . . . 426 Canal de Riego de Lajas above Majinas Filtration Plant (d) . . . . . . . . . . . . . . . . . . . . . . . 50128920 . . . . . . . . . . . . 428 Canal de Riego de Lajas below Majinas Filtration Plant (d) . . . . . . . . . . . . . . . . . . . . . . . 50128925 . . . . . . . . . . . . 430 Canal de Riego de Lajas above Lajas Filtration Plant at Lajas (d) . . . . . . . . . . . . . . . . . . . 50128935 . . . . . . . . . . . . 432 Canal de Riego de Lajas below Lajas Filtration Plant at Lajas (d) . . . . . . . . . . . . . . . . . . . 50128940. . . . . . . . . . . . . 434 Canal de Riego de Lajas at Bo. Palmarejo near Lajas (d) . . . . . . . . . . . . . . . . . . . . . . . . . . 50128945 . . . . . . . . . . . . 436 Río Loco at Guanica (c,b,p) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50129700 . . . . . . . . . . . . 438 RIO GUANAJIBO BASIN Río Guanajibo near San Germán (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50133600 . . . . . . . . . . . . 442 Río Rosario near Hormigueros (d,c,b,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50136400 . . . . . . . . . . . . 444 Río Guanajibo near Hormigueros (d,c,b,p) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50138000 . . . . . . . . . . . . 451 RIO YAGÚEZ Río Yagüez near Mayagüez (c,b). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50138800. . . . . . . . . . . . . .456 RIO GRANDE DE AÑASCO BASIN Lago Guayo at Damsite near Castañer (e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50141500 . . . . . . . . . . . . 458 Río Grande de Añasco near Lares (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50143000. . . . . . . . . . . . . .460 Río Grande de Añasco near San Sebastián (d,c,b). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50144000 . . . . . . . . . . . . 462 RIO CULEBRINAS BASIN Río Culebrinas near San Sebastián (c,b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50147600 . . . . . . . . . . . . 470 Río Culebrinas at Highway 404 near Moca (d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50147800 . . . . . . . . . . . . 472 Río Culebrinas at Margarita Dam near Aguada (d,s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50148890 . . . . . . . . . . . . 474 xi GROUND-WATER WELLS, BY BASIN, FOR WHICH RECORDS ARE PUBLISHED Page RIO GUAJATACA BASIN 182422067015100. Local number, 165. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 182647066552400. Local number, 202. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483 RIO CAMUY BASIN 182723066511200. Local number, 1026. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484 RIO GRANDE DE ARECIBO BASIN 182756066454700. Local number, 1051 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485 182737066370900. Local number, 204. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491 182616066364100. Local number, 1052. 182626066345100. Local number, 1053. 182639066385200. Local number, 1056. 182209066340600. Local number, 1057. RIO GRANDE DE MANATI BASIN 182544066341500. Local number, 205. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492 182549066304300. Local number, 166. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493 182506066280200. Local number, 1076. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494 182308066260400. Local number, 210. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495 RIO CIBUCO BASIN 182712066251700. Local number, 1102. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496 182615066235300. Local number, 211. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497 182647066201700. Local number, 70. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498 182330066185700. Local number, 213. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 499 RIO DE LA PLATA BASIN 182526066165001. Local number, 1127. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 182548066164401. Local number, 1128. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 501 182620066163403. Local number, 1130. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502 182657066162701. Local number, 1132. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503 182654066150600. Local number, 1133. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504 182530066135400. Local number, 216. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 505 180649066095500. Local number, 1134. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 506 RIO HONDO TO RIO PUERTO NUEVO BASINS 182441066082600. Local number, 219. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507 182531066075900. Local number, 652. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 182435066052700. Local number, 1153. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512 182445066043401. Local number, 1154. 182406066034700. Local number, 1158. 182451066080200. Local number, 1159. RIO GRANDE DE LOIZA BASIN 181352066025300. Local number, 1176. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513 181311066022500. Local number, 1177. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514 181539066014500. Local number, 1179. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515 182515065594100. Local number, 222. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516 RIO HERRERA TO RIO ANTON RUIZ BASINS 181217065453000. Local number, 1203. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517 182131065421100. Local number, 1205. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 518 181917065382701. Local number, 1207. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 519 182234065440000. Local number, 1208. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 520 xii GROUND-WATER WELLS, BY BASIN, FOR WHICH RECORDS ARE PUBLISHED--Continued Page RIO HUMACAO TO QUEBRADA AGUAS VERDES BASINS 180415065513900. Local number, 96. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 521 175855066050500. Local number, 1228. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522 1757280660722000. Local number, 1229. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523 175719066085500. Local number, 1230. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524 175858066100200. Local number, 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525 175947066130601. Local number, 1233. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526 175814066102200. Local number, 1239. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527 RIO SALINAS TO RIO JACAGUAS BASINS 175809066133100. Local number, 1251. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528 529 530 531 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532 180104066152300. Local number, 1253. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175910066155500. Local number, 1254. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175903066165000. Local number, 1256. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175943066224800. Local number 1257. 175829066232200. Local number, 87. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534 535 536 537 538 539 540 180020066261500. Local number, 1258. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180602066133100. Local number, 1260. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175833066145800. Local number, 1261. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175735066151800. Local number, 1262. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175734066233300. Local number, 146. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175843066244100. Local number, 1263. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RIO INABON TO RIO LOCO BASINS 175950066354200. Local number, 141. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541 175934066364800. Local number, 1276. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 542 RIO INABON TO RIO LOCO BASIN 180045066381600. Local number 1277. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544 RIO INABON TO RIO LOCO BASINS 180156066434000. Local number, 1278. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545 180133066503300. Local number, 132. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 546 RIO GUANAJIBO BASIN 180132067033800. Local number, 143. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 547 180542067084000. Local number, 1301. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548 RIO CULEBRINAS BASIN 182017067143300. Local number, 1352. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550 182442067091700. Local number, 200. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551 ST. CROIX, U.S. VIRGIN ISLANDS 174225064472000. Local number, 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554 174243064475100. Local number, 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555 174316064480800. Local number, 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556 ST. THOMAS, U.S. VIRGIN ISLANDS 182038064550300. Local number, 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558 182038064580000. Local number, 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559 ST. JOHN, U.S. VIRGIN ISLANDS 181956064464500. Local number, 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560 -- -- -- -- -- -- -- -- -- xiii DISCONTINUED STREAMFLOW STATIONS The following continuous-record streamflow stations in Puerto Rico and the U.S. Virgin Islands have been discontinued or converted to partial-record stations. Daily streamflow or stage records were collected for the period of record shown for each station. Station number Station name Drainage area (mi2) Period of record 50007000 Quebrada de los Cedros near Isabela 6.91 1970 50010600 Río Guajataca above Lago de Guajataca 1984-89 50011000 Canal Diversion Lago Guajataca 1970 50011200 Río Guajataca below Lago Guajataca 1969-70,1984-87 50011400 Río Guajataca above mouth near Quebradillas 1969-70,1984-89 50013000 Río Camuy near Lares 7.62 1969-71 50014000 Río Criminales near Lares 4.68 1969-70 50014600 Río Camuy at Tres Pueblos Sinkhole 1990-96 50015700 Río Camuy near Hatillo 1984-96 50016000 Río Camuy near Camuy 1969-73 50021050 Río Pellejas below Central Pellejas 7.89 1972-75 50021500 Río Pellejas near Utuado 9.55 1969-71 50023000 Río Viví near Central Pellejas 5.66 1969-75 50027200 Río Grande de Arecibo below Lago Dos Bocas 169 1970-71 50027250 Río Grande de Arecibo below Lago Dos Bocas near Florida 170 2000-2002 50027750 Río Grande de Arecibo above Arecibo 170 1982-2002 50031500 Río Sana Muerto near Orocovis 3.68 1965-70 50035200 Río Grande de Manatí at Hwy 145 at Ciales 132 1972 50035950 Río Cialitos at Hwy 649 at Ciales 17 1970-82 50038360 Río Mavilla near Corozal 9.51 1969-70 50038600 Río Unibón near Morovis 5.29 1969-70 50038700 Río Morovis at Morovis 1.26 1968 50038900 Río Indio at Vega Baja 1963,66,71 50039600 Río Cibuco at Central San Vicente 1969-72 50043200 Río Usabon near Barranquitas 9.15 1968-69,71 50043400 Río Aibonito Tributary near Aibonito 1.13 1968-71 50044600 Río Guadiana near Naranjito 1.73 1971 50044650 Quebrada del Toro near Naranjito 0.54 1971 50044800 Quebrada Anones near Naranjito 2.32 1971 50045700 Río Lajas at Toa Alta 8.65 1966-75 50047540 Río Sabana at Vista Monte 0.80 1993,1994-2002 50047820 Río de Bayamón at Hwy 174 near Bayamón 31.90 1966 50048000 Río de Bayamón at Bayamón 71.90 1963-67 50049000 Río Piedras at Río Piedras 12.5 1971-82, 1987-93 50049310 Quebrada Josefina at Piñero Avenue 3.84 1988-91 50051150 Quebrada Blanca at El Jagual 3.25 1984-2002 50053050 Río Turabo at Borinquen 7.89 1984-90 50054000 Quebrada de las Quebradillas near Caguas 6.25 1969-71,73 50055170 Río Cagüitas near Caguas 8.27 1992-97 50055390 Río Bairoa at Bairoa 5.08 1990-2001 xiv DISCONTINUED STREAMFLOW STATIONS--Continued Station Station name Drainage Period of number area (mi2) record 50055650 Quebrada Caimito near Juncos 0.82 1984-87 50056000 Río Valenciano near Las Piedras 6.85 1971 50056900 Quebrada Mamey near Gurabo 2.30 1984-92 50058300 Quebrada Arena near Caguas -- 1971 50061300 Río Canovanillas near Loíza 14.40 1968-73 50062500 Río Herrera near Colonia Dolores 2.75 1968-72 50063300 Río Espíritu Santo near El Verde 2.23 1968-73 50063500 Quebrada Toronja at El Verde 0.064 1983-96 50065700 Río Mameyes at Hwy 191 at Mameyes 11.80 1967-85 50070500 Río Fajardo above Fajardo 3.69 1995-2001 50072000 Río Fajardo at Fajardo 21.60 1960-63 50073200 Río Daguao at Daguao 2.26 1966-82 50073400 Quebrada Palma at Daguao 4.84 1972-77 50074000 Río Santiago at Naguabo 4.99 1966-82 50075500 Río Blanco at Florida 11.00 1966-82 50077000 Río Blanco at Río Blanco 17.60 1973-77 50077400 Río Blanco at Colonia La Fe 18.80 1967-70 50078500 Río Anton Ruíz at Central Pasto Viejo 4.33 1968 50081500 Río Humacao near Humacao 9.23 1973 50082000 Río Humacao at Hwy 3 at Humacao 17.30 1983-85 50082200 Río Humacao near La Suiza 19.90 1965-66, 1969-71 50082800 Río Guayanés near Colonia Laura 4.69 1969-82 50083500 Río Guayanés near Yabucoa 17.20 1969-71 50084000 Río Limones near Yabucoa 7.89 1969-71 50085100 Río Guayanés at Central Roig 26.60 1965-66, 1968,70 50086100 Río del Ingenio at Comunas 5.50 1965-66, 1968-69 50086500 Río Guayanés at Playa Guayanés 34.00 1965-66, 1968-71 50087200 Caño Santiago near Central Roig 6.04 1965-71 50091000 Río Maunabo at Maunabo 12.40 1965,67, 1969-82 50091200 Río Maunabo near Maunabo 12.70 1971-72 50091400 Río Jacaboa near Lamboglia 4.13 1965-73 50091700 Río Chico at Patillas 6.82 1965, 1969-72 50091800 Río Chico at Providencia 4.90 1965, 1967-69, 1971 50094200 Río Grande de Patillas at Patillas 27.90 1967, 1969, 1971 50094300 Río Grande de Patillas at Providencia 29.00 1971 50094400 Río Nigua at Pitahaya 50095200 Río Guamaní at Guayama 50095500 Río Guamaní near Guayama 50099000 Quebrada Aguas Verdes near Salinas 50106500 Río Coamo near Coamo 5.86 1965, 1969, 1970-71, 1973 8.22 1969-71 12.30 1969-70 0.39 1989 46.00 1967-68, 1984-85, 1986 50106900 Río Coamo below Lago Coamo near Coamo 65.40 1967-68 50107200 Río Coamo at mouth near Santa Isabel 69.30 1967-68 50108200 Río Descalabrado at Las Ollas 13.90 1965, 1967-71 50108500 Río Descalabrado near Santa Isabel 18.10 1966-67 50111200 Río Toa Vaca near Villalba 21.40 1966-70 xv DISCONTINUED STREAMFLOW STATIONS--Continued Station Station name Drainage Period of number area (mi2) record 50111700 Río Jacaguas near Juana Díaz 53.20 1966-68 50111750 Río Jacaguas below Quebrada Guanábana 56.30 1989 50112100 Río Jacaguas near Arús 59.60 1966-67 50112600 Río Inabón at Coto Laurel -- 1967-71 50113100 Río Guayo near Coto Laurel 11.80 1965, 1968-71 50113500 Río Inabón near Arús 30.20 1964-65 50114390 Río Bucaná at Hwy 14 Bridge near Ponce 24.9 1987-2002 50114400 Río Bucaná near Ponce 25.60 1965-81 50114700 Río Bucaná near Playa de Ponce 28.40 1964-67 50115000 Río Portugués near Ponce 8.82 1964-97 50116500 Río Portugués at Highway 2 Bypass at Ponce 20.50 1964-65 50119000 Río Matilde at Ponce 19.40 1965-66 50121000 Río Tallaboa at Peñuelas 24.20 1959-82 50122000 Río Tallaboa at Tallaboa 31.50 1959-63 50124000 Río Guayanilla nr Guayanilla 18.50 1961-69 50124500 Río Guayanilla at Guayanilla 20.80 1971-82 50125900 Río Duey above Diversion near Yauco 8.93 1977-80 50128000 Río Yauco near Yauco 45.50 1962-64, 1977-85 50129000 Río Loco near Yauco 8.50 1963-67 50129500 Río Loco near Guánica 21.00 1963-69 50129900 Laguna Cartagena near Boquerón -- 1984-86 50130320 Quebrada Mamey at Joyuda 0.38 1986-88 50136000 Río Rosario at Rosario 16.40 1975-86 50141000 Río Yahuecas near Adjuntas 15.40 1980-85 50145000 Río Grande de Añasco at El Espino 108.00 1959-66, 1961-63 50147000 Río Culebrinas at San Sebastian 16.70 1960-82 50214500 Quebrada Resaca near Monte Resaca, Culebra 0.23 1991-93 50215000 Drainage Canal at Culebra Airport, Culebra 0.08 1991-93 50231000 Quebrada Confresí Tributary near Isabel II, Vieques 0.28 1991-93 50232000 Quebrada La Mina near Esperanza, Vieques 0.68 1991-96 50233000 Quebrada Pilón at Colonia Puerto Real, Vieques 0.67 1991-96 50276000 Turpentine Run at Mariendal, St.Thomas 2.97 1963-69, 1978-86 50292600 Lameshur Bay Gut at Lameshur, St. John 0.38 1992-94 50294000 Fish Bay Gut at Fish Bay, St. John 1.48 1992-94 50295500 Cruz Bay Gut at Cruz Bay, St. John, VI 0.09 1992-93 50332000 River Gut at River 1.42 1991-93 50333500 River Gut near Golden Grove 5.40 1990-93 50333700 River Gut at Hwy 66 at Fairplanes 5.89 1990-96 50334500 Bethehem Gut at Hwy 66 at Fairplanes 4.11 1990-96 50337500 Gut 4.5 at Cane Valley 0.2 1991-93 50348000 Salt River at Canaan 0.36 1991-93 50349000 Gut 10 near Altona 0.13 1991-93 xvi THIS PAGE IS INTENTIONALLY BLANK 1 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 INTRODUCTION The Water Resources Division of the U.S. Geological Survey, in cooperation with local and Federal agencies obtains a large amount of data pertaining to the water resources of the Commonwealth of Puerto Rico and the Territory of the U.S. Virgin Islands each water year. These data, accumulated during many water years, constitute a valuable data base for developing an improved understanding of the water resources of the area. To make these data readily available to interested parties outside the U.S. Geological Survey, the data are published annually in this report series entitled "Water Resources Data for Puerto Rico and the U.S. Virgin Islands, 2003." This report includes records on both surface and ground water. Specifically, it contains: (1) discharge records for 86 streamflow-gaging stations, daily sediment records for 22 sediment stations, stage records for 18 reservoirs, and (2) water-quality records for 17 streamflow-gaging stations, and for 42 ungaged stream sites, 13 lake sites, 2 lagoons, and 1 bay, and (3) water-level records for 72 observation wells. Water-resources data for Puerto Rico for calendar years 1958-67 were released in a series of reports entitled "Water Records of Puerto Rico." Water-resources data for the U.S. Virgin Islands for the calendar years 1962-69 were released in a report entitled "Water Records of U.S. Virgin Islands." Included were records of streamflow, ground-water levels, and water-quality data for both surface and ground water. Beginning with the 1968 calendar year, surface-water records for Puerto Rico were released separately on an annual basis. Ground-water level records and water-quality data for surface and ground water were released in companion reports covering periods of several years. Data for the 1973-74 reports were published under separate covers. Water-resources data reports for 1975 to 2001 water years consist of one volume each and contain data for streamflow, water quality, and ground water. Publications similar to this report are published annually by the U.S. Geological Survey for all States. These official Survey reports have an identification number consisting of the two-letter State abbreviation, the last two digits of the water year, and the volume number. For example, this volume is identified as "U.S. Geological Survey Water-Data Report PR-02-1." These water-data reports are for sale in paper copy or in microfiche by the National Technical Information Service, U.S. Department of Commerce, Springfield, Virginia, 22161. Additional information, including current prices, for ordering specific reports may be obtained from the District Chief at the address given on back of the title page or by telephone (787) 749-4346. 2 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 COOPERATION The U.S. Geological Survey has had cooperative agreements with organizations of the Commonwealth of Puerto Rico and the Territory of the U.S. Virgin Islands for the systematic collections of water resources data since 1958. Organizations that supplied data are acknowledged in the station descriptions. Organizations that assisted in collecting data through cooperative agreements with the U.S. Geological Survey are: Puerto Rico Environmental Quality Board Puerto Rico Aqueduct and Sewer Authority Puerto Rico Department of Agriculture Puerto Rico Industrial Development Company Puerto Rico Highway Authority Puerto Rico Department of Natural and Environmental Resources Puerto Rico Department of Health Puerto Rico Electric Power Authority Puerto Rico Solid Waste Management Authority Puerto Rico Legislature Puerto Rico Emergency Management Agency U.S. Virgin Islands Department of Planning and Natural Resources Puerto Rico Infrastructure Financing Authority Funds were also provided by the U.S. Army, Corps of Engineers, for the collection of records at six gaging stations published in this report. 3 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 SUMMARY OF HYDROLOGIC CONDITIONS Precipitation Islandwide annual rainfall during water year 2003 (October 2002 to September 2003), was 93 percent below normal rainfall conditions. Annual rainfall averaged about 90 percent of normal in northern Puerto Rico, 90 percent of normal in southern Puerto Rico, 87 percent of normal in western Puerto Rico, and 106 percent of normal in eastern Puerto Rico. Normal rainfall is defined as the mean monthly rainfall for certain period of time. In Puerto Rico, the reference period used to define the monthly normal rainfall is 1971-2000 (table 1). During nine months, the rainfall was below the monthly normal rainfall (table 1). Significant deficient rainfall conditions were registered during October (27 percent below normal), November (47 percent below normal), May (41 percent below normal), and June (31 percent below normal). This significant rainfall deficiency was registered during part of the wet seasons. Recorded rainfall during the nine below-normal months averaged from 12 to 47 percent below monthly normal rainfall. During January, April, and August the rainfall throughout the Island was above normal rainfall conditions. Monthly rainfall during April (12.33 inches) almost triplicates the normal rainfall amount for this month (4.19 inches). This abnormal rainfall condition was generated by a strong upper level trough system combined with abundant moisture conditions which produced very heavy rainfall across Puerto Rico and the U.S. Virgin Islands during April 17 and 18, 2003. Rainfall throughout the U.S. Virgin Islands was deficient during water year 2003 with an annual rainfall average of 75 percent of normal. Monthly normal rainfall was below normal during ten months of the water year 2003. During these months, the normal rainfall averaged from 12 to 72 percent below monthly normal rainfall. As mentioned above, the U.S. Virgin Islands experienced very heavy rainfall during April 17 and 18, 2003. As much as 5.68 inches of rain was recorded at St. Thomas during 48-hour period. During April, the normal rainfall in the U.S. Virgin Islands was about 290 percent above normal. Table 1. Islandwide monthly rainfall for the water year 2003 and monthly normal rainfall for the 30-year reference period, 1971-2000. Data from the National Oceanographic and Atmospheric Administration Month 2003 Water Year (inches) 30-year normal (inches) October 5.84 7.98 November 3.48 6.53 December 3.16 4.05 January 3.76 3.20 February 2.56 2.90 March 2.24 2.96 April 12.33 4.19 May 3.94 6.67 June 3.07 4.46 July 4.32 4.88 August 6.76 6.51 September 6.33 7.91 TOTAL 57.79 62.24 4 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Surface Water Streamflow in Puerto Rico during most of the water year 2003 (October 1, 2002 to September 30, 2003), was below or near normal streamflow conditions, based on the index stations which are representative of the four geographical areas (figure 1). During this period of record, there was only one significant rainfall event that produced excessive rainfall which increased the streamflows islandwide. This rainfall event produced by a strong upper level trough combined with abundant moisture affected Puerto Rico and the U.S. Virgin Islands during April 17 and 18, 2003. Moderate to severe flooding occurred across areas of southern and eastern Puerto Rico. Comparisons of the monthly mean flows during water year 2003 with the long-term minimum, median, and maximum of the monthly mean flows, for the period of record at the index stations on the Río Grande de Manatí (northern area), the Río Fajardo (eastern area), the Río Inabón (southern area), and the Río Grande de Añasco (western area) are shown in figure 1. An overview describing the hydrologic conditions during water year 2003 at the four areas represented by the index stations are discussed next. In the northern area, the Río Grande de Manatí index station registered monthly mean flows below normal during the first six months and last four months of the water year. During these ten months, the monthly mean flows were from 28 to 61 percent below of the long-term median. The monthly mean flow was above normal during April while the monthly mean flow during May equaled the long-term median of the monthly mean flows. During April, the monthly mean was 166 percent above the long-term median of the monthly mean flows. In the eastern area, streamflow conditions, as showed by the Río Fajardo index station, were near normal during seven months of the water year. The monthly mean flow during October equaled the long-term median of the monthly mean flows. The historical minimum monthly mean flow was equaled during November and a historical minimum monthly mean flow was registered during March. During April, a historical maximum monthly mean was recorded at the Río Fajardo index station. In this station, the monthly mean flows ranged from 78 percent below normal during March to 381 percent above normal during April. The southern area that use to be dryer than the other areas, also showed below normal streamflow conditions but in less degree compared with the northern and eastern areas. Streamflow conditions, as recorded by the Río Inabón index station, were below normal during October, November, March, June, July, August, and September. The monthly mean flow during December equaled the long-term median of the monthly mean flows. During four months, January, February, April, and May, the monthly mean flows were above the long-term median of the monthly mean flows. Monthly mean flows recorded at the Río Inabón index station ranged from 60 percent below normal during July to 192 percent above normal during May. Streamflows registered at the Río Grande de Añasco index station serves to indicate the hydrologic conditions at the western area during water year 2003. Monthly mean flows in this area was in general, near normal or above normal during most of the water year. During November, December, January, April, May, and June, the Río Grande de Añasco index station registered monthly mean flows above the long-term median of the monthly mean flows. During October, the monthly mean flow was very close to the historical minimum monthly mean flow. Monthly mean flows were slightly below normal during the months of March, July, August, and September. The monthly mean flow during February equaled the long-term median of the monthly mean flows. At the Río Grande de Añasco index station, the monthly mean flows ranged from 48 percent below normal during October to 148 above normal during May. 5 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Figure 1. Monthly-mean discharge of selected streams in Puerto Rico. 6 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Ground Water In Puerto Rico and the Virgin Islands, water year 2003 was a period of declining ground-water levels. Declining water level means that storage in the aquifer is declining. In Puerto Rico, 70 percent of all wells showed a decline for the year. In the Virgin Islands, ground-water levels at all the wells declined. One region where ground water levels rose was in the San Juan metropolitan area extending south to Caguas and Cayey and east to Luquillo and Fajardo. The only significant recharge event was the April 17-18, 2003 rainfall event. On these two days the National Weather Service identified 11 municipios that received from 7 to 22 inches of rain. The rains caused widespread flooding in northeastern Puerto Rico. At a number of wells this rainfall event caused ground-water levels to rise but not enough to reverse the downward trend for the year as a whole. Two ground-water stations hit record highs in water year 2003 (table 2). Piezometer Ft. Buchanan 1 continued a nine-year trend of gradually rising water levels and hit a record high. The rains on April 17, 2003, caused Piezometer Carlos Arroyo 1 to reach a record high. Ten ground-water stations reached record lows in water year 2003 (table 3). Cruce Dávila NC 5 is in the Lower Aquifer of the North Coast Limestone Ground Water Province and has been declining steadily for 15 years. Most months it establishes a new record low. No other ground-water station in Puerto Rico has maintained consistently downward trends as this one. Most of the wells that reached new record lows were on the south coast from Guayama to Santa Isabel and have records that began in 1997, which means that there is no data from the drought of the mid 90s. The record lows at Jobitos Battery and Godreau 7 were significant because both of these stations reached record lows although they have records only since 1991. At these two locations, water year 2003 was drier than the mid 90s which was a time of water rationing in most areas of the island. 7 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Figur e 2. Ground-water levels at selected wells in Puerto Rico and the U.S. Virgin Islands. 8 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Table 2. Highest ground-water levels recorded during 2003 water year and previous high ground-water levels at selected wells in Puerto Rico. [PR, Puerto Rico; +, water level above land-surface datum; ft-blsd, feet below land-surface datum; mm-dd-yy, month-day-year; mm-yy, month-year] 2003 Previous highest highest Period of Local water level Date water level Date record Well name number Location (ft-blsd) (mm-dd-yy) (ft-blsd) (mm-dd-yy) (mm-yy) Piezometer 1159 PR 24.91 09-11-03 25.54 09-25-02 09-97 to 09-03 Fort Buchanan 1 Piezometer 1203 PR 1.55 04-17-03 1.66 11-13-99 10-97 to 09-03 Carlos Arroyo 1 Table 3. Lowest ground-water levels recorded during 2003 water year and previous lowest ground-water levels at selected wells in Puerto Rico. [PR, Puerto Rico; ft-blsd, feet below land-surface datum; mm-dd-yy, month-day-year; mm-yy, month-year] 2003 Previous lowest lowest Period of Local water level Date water level Date record Well name number Location (ft-blsd) (mm-dd-yy) (ft-blsd) (mm-dd-yy) (mm-yy) NC-5 Cruce Dávila 205 PR 104.78 09-15-03 96.61 08-27-02 12-86 to 09-03 Piezometer 1128 PR 29.49 07-21-03 29.44 06-23-01 06-95 to 09-03 Maguayo 2 06-24-01 Piezometer 1130 PR 36.33 06-29-03 36.15 05-01-95 01-95 to 09-03 Higuillar 4 05-11-95 05-13-95 06-16-01 06-17-01 Algarrobo 1228 PR 34.62 12-09-02 34.19 07-19-01 05-97 to 09-03 Domestic 1 07-20-01 Barranca Dug 1229 PR 24.69 03-14-03 24.21 06-07-97 04-97 to 09-03 06-08-97 06-09-97 Jobos 1239 PR 37.39 09-10-03 32.63 09-30-02 04-97 to 09-03 Coqui BTR 1 1251 PR 19.97 09-23-03 18.64 05-29-98 03-97 to 09-03 Piezometer 1254 PR 52.19 04-07-03 47.98 10-07-97 02-97 to 09-03 USGS D Godreau 7 1256 PR 36.96 08-25-03 34.87 09-03-96 09-91 to 09-03 to 09-06-03 Bauzá 1 1260 PR 232.84 08-25-03 to 219.20 08-26-02 10-97 to 09-03 09-06-03 Jobitos BTR 1263 PR 45.81 08-01-03 45.73 09-16-94 09-91 to 09-03 03-15-03 09-17-94 9 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Water Quality The U.S. Geological Survey, in cooperation with several Commonwealth agencies, collected water-quality data at 60 surface-water stations during water year 2003. Water-quality data collected at these stations included major ions, trace elements, nutrients, pesticides, as well as fecal indicator bacteria and physical parameters. The presence of high concentrations of fecal coliform (fig. 3) and fecal streptococcal (fig. 4) bacteria during water year 2003 continued to be one of the principal water-quality problems in Puerto Rico. Although water pollution control measures are being implemented to decrease the concentrations of these bacteria and even when there has been an improvement in the water quality of the majority of the streams in comparison with previous years, the values are still above the established water-quality standards for natural waters. Areas drained by major rivers where there is intense land use (agriculture, industry, urbanization) have, in general, fairly high concentrations of fecal indicator bacteria. The ability of communities to treat drinking water for bacteria is often inhibited by runoff with high suspended-sediment concentration and the associated turbidity problems. This is generally the principal cause in streams which suffer from intense resource utilization (agriculture and urban development) where soil movement is involved. The U.S. Geological Survey, in cooperation with various Commonwealth and Federal agencies, collected suspended-sediment samples at 22 stations in Puerto Rico during the 2003 water year. High suspended-sediment concentrations are a common problem in many streams in Puerto Rico. Most of the streams with high suspended- sediment concentrations are related to land use, especially urban development, agriculture, and activities which disturb soil cover. High suspended-sediment concentrations affect the operation of public surface-water supply filtration plants and contribute with the storage depletion capacities of reservoirs. Table 4 summarizes the annual sediment discharge (in tons) and sediment yield (in tons/mi²), for some of the monitored stations. Calculated sediment yields varied from a minimum of 62.7 tons/mi² at station 50027600, Río Grande de Arecibo near San Pedro, to a maximum of 10,500 tons/mi² at station 50048770, Río Piedras at El Señorial. The average sediment yield was 1,730 tons/mi² and the median was 1,160 tons/mi². 10 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Figure 3. Location of maximum concentrations of fecal coliform bacteria at the water-quality sampling sites in Puerto Rico. 11 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Figure 4. Location of maximum concentrations of fecal streptococci bacteria at the water-quality sampling sites in Puerto Rico. 12 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Table 4. Sediment yields at selected sediment stations for water year 2003. [mi², square miles; tons/mi², tons per square miles] Station Station Drainage area, Annual sediment Sediment yields, number name in mi² discharge, in tons in tons/mi² 50020500 Río Grande de Arecibo near Adjuntas 12.7 28,500 2,240 50021030 Río Pellejas above Central Pellejas 6.83 8,330 1,220 50021700 Río Grande de Arecibo Above Utuado 36.0 27,500 764 50024950 Río Grande de Arecibo below Utuado 65.6 106,000 1,620 50025155 Río Saliente at Coabey near Jayuya 9.25 2,370 256 50025850 Río Jauca at Paso Palma 6.89 3,730 541 50026025 Río Caonillas at Paso Palma 37.9 23,100 609 50026400 Río Yunes at Hwy 140 near Florida 13.9 16,200 1,160 50027000 Río Limón above Lago Dos Bocas 33.2 53,700 1,620 50027600 Río Grande de Arecibo near San Pedro 173.7 10,900 63 50028000 Río Tanamá near Utuado 18.4 14,700 799 50031200 Río Grande de Manatí near Morovis 55.2 31,400 569 50035000 Río Grande de Manatí at Ciales 128 122,000 953 50043800 Río de la Plata at Comerío 109 154,000 1,410 50027000 Río Limón above Lago Dos Bocas 33.2 53,700 1,620 50048770 Río Piedras at El Señorial 7.49 78,600 10,500 50055000 Río Grande de Loíza at Caguas 89.8 67,900 756 50065500 Río Mameyes near Sabana 6.88 8,940 1,300 50071000 Río Fajardo near Fajardo 14.9 47,400 3,180 50136400 Río Rosario near Hormigueros 18.3 10,700 585 50148890 Río Culebrinas at Margarita Dam near 94.6 424,000 4,480 Aguada 13 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 SPECIAL NETWORKS AND PROGRAMS Hydrologic Benchmark Network is a network of 61 sites in small drainage basins in 39 States that was established in 1963 to provide consistent streamflow data representative of undeveloped watersheds nationwide, and from which data could be analyzed on a continuing basis for use in comparison and contrast with conditions observed in basins more obviously affected by human activities. At selected sites, water-quality information is being gathered on major ions and nutrients, primarily to assess the effects of acid deposition on stream chemistry. Additional information on the Hydrologic Benchmark Program may be accessed from http://water.usgs.gov/hbn/ National Stream-Quality Accounting Network (NASQAN) is a network of sites used to monitor the water quality of large rivers within the Nation’s largest river basins. From 1995 through 1999, a network of approximately 40 stations was operated in the Mississippi, Columbia, Colorado, and Rio Grande River basins. For the period 2000 through 2004, sampling was reduced to a few index stations on the Colorado and Columbia Rivers so that a network of 5 stations could be implemented on the Yukon River. Samples are collected with sufficient frequency that the flux of a wide range of constituents can be estimated. The objective of NASQAN is to characterize the water quality of these large rivers by measuring concentration and mass transport of a wide range of dissolved and suspended constituents, including nutrients, major ions, dissolved and sediment-bound heavy metals, common pesticides, and inorganic and organic forms of carbon. This information will be used (1) to describe the long-term trends and changes in concentration and transport of these constituents; (2) to test findings of the National Water-Quality Assessment (NAWQA) Program; (3) to characterize processes unique to large-river systems such as storage and re-mobilization of sediments and associated contaminants; and (4) to refine existing estimates of off-continent transport of water, sediment, and chemicals for assessing human effects on the world’s oceans and for determining global cycles of carbon, nutrients, and other chemicals. Additional information about the NASQAN Program may be accessed from http://water.usgs.gov/nasqan/. The National Atmospheric Deposition Program/National Trends Network (NADP/NTN) is a network of monitoring sites that provide continuous measurement and assessment of the chemical constituents in precipitation throughout the United States. As the lead Federal agency, the USGS works together with over 100 organizations to provide a long-term, spatial and temporal record of atmospheric deposition generated from this network of 250 precipitation-chemistry monitoring sites. The USGS supports 74 of these 250 sites. This long-term, nationally consistent monitoring program, coupled with ecosystem research, provides critical information toward a national scorecard to evaluate the effectiveness of ongoing and future regulations intended to reduce atmospheric emissions and subsequent impacts to the Nation’s land and water resources. Reports and other information on the NADP/ NTN Program, as well as data from the individual sites, may be accessed from http://bqs.usgs.gov/acidrain/. The USGS National Water-Quality Assessment (NAWQA) Program is a long-term program with goals to describe the status and trends of water-quality conditions for a large, representative part of the Nation’s ground- and surface-water resources; to provide an improved understanding of the primary natural and human factors affecting these observed conditions and trends; and to provide information that supports development and evaluation of management, regulatory, and monitoring decisions by other agencies. Assessment activities are being conducted in 42 study units (major watersheds and aquifer systems) that represent a wide range of environmental settings nationwide and that account for a large percentage of the Nation’s water use. A wide array of chemical constituents is measured in ground water, surface water, streambed sediments, and fish tissues. The coordinated application of comparative hydrologic studies at a wide range of spatial and temporal scales will provide information for water-resources managers to use in making decisions and a foundation for aggregation and comparison of findings to address water-quality issues of regional and national interest. 14 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Communication and coordination between USGS personnel and other local, State, and Federal interests are critical components of the NAWQA Program. Each study unit has a local liaison committee consisting of representatives from key Federal, State, and local water-resources agencies, Indian nations, and universities in the study unit. Liaison committees typically meet semiannually to discuss their information needs, monitoring plans and progress, desired information products, and opportunities to collaborate efforts among the agencies. Additional information about the NAWQA Program may be accessed from http://water.usgs.gov/nawqa/. The USGS National Streamflow Information Program (NSIP) is a long-term program with goals to provide framework streamflow data across the Nation. Included in the program are creation of a permanent Federally funded streamflow network, research on the nature of streamflow, regional assessments of streamflow data and databases, and upgrades in the streamflow information delivery systems. Additional information about NSIP may be accessed from http://water.usgs.gov/nsip/. EXPLANATION OF RECORDS The surface- and ground-water records published in this report are for the 2002 water year that began October 1, 2001 and ended September 30, 2002. A calendar of the water year is provided on the inside of the front cover. The records contain streamflow data, water-quality data for surface and ground water, and ground-water-level data. The locations of the stations and wells where the data were collected are shown in figures 3 to 8. The following sections of the introductory text are presented to provide users with a more detailed explanation of how the hydrologic data published in this report were collected, analyzed, computed, and arranged for presentation. DOWNSTREAM ORDER AND STATION NUMBER Since October 1, 1950, hydrologic-station records in USGS reports have been listed in order of downstream direction along the main stream. All stations on a tributary entering upstream from a main-stream station are listed before that station. A station on a tributary entering between two main-stream stations is listed between those stations. A similar order is followed in listing stations on first rank, second rank, and other ranks of tributaries. The rank of any tributary on which a station is located with respect to the stream to which it is immediately tributary is indicated by an indention in that list of stations in the front of this report. Each indentation represents one rank. This downstream order and system of indentation indicates which stations are on tributaries between any two stations and the rank of the tributary on which each station is located. As an added means of identification, each hydrologic station and partial-record station has been assigned a station number. These station numbers are in the same downstream order used in this report. In assigning a station number, no distinction is made between partial-record stations and other stations; therefore, the station number for a partial-record station indicates downstream-order position in a list composed of both types of stations. Gaps are consecutive. The complete 8-digit (or 10-digit) number for each station such as 50028000, which appears just to the left of the station name, includes a 2-digit part number “50” plus the 6-digit (or 8-digit) downstream order number “028000.” In areas of high station density, an additional two digits may be added to the station identification number to yield a 10-digit number. The stations are numbered in downstream order as described above between stations of consecutive 8-digit numbers. 15 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Figur e 5. Location of surface-water stations in Puerto Rico. 16 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Figur e 6. Location of water-quality stations in Puerto Rico. 17 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Figur e 7. Location of ground-water stations in Puerto Rico. 18 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Figure 8. Location of ground-water stations in the U.S. Virgin Islands. 19 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 NUMBERING SYSTEM FOR WELLS AND MISCELLANEOUS SITES The 8-digit downstream order station numbers are not assigned to wells and miscellaneous sites where only random water-quality samples or discharge measurements are taken. The well and miscellaneous site numbering system of the U.S. Geological Survey is based on the grid system of latitude and longitude. The system provides the geographic location of the well or miscellaneous site and a unique number for each site. The number consists of 15 digits. The first 6 digits denote the degrees, minutes, and seconds of latitude, the next 7 digits denote degrees, minutes, and seconds of longitude, and the last 2 digits (assigned sequentially) identify the wells or other sites within a 1-second grid. The numbers shown in the grid correspond to the local numbers assigned to each well as visited in the field. An example is well 16 (fig. 9). Figure 9. System for numbering wells and miscellaneous sites (latitude and longitude). EXPLANATION OF STAGE AND WATER DISCHARGE RECORDS Data Collection and Computation The base data collected at gaging stations (figs. 5 and 8) consist of records of stage and measurements of discharge of streams or canals, and stage, surface area, and volume of lakes or reservoirs. In addition, observations of factors affecting the stage-discharge relation or the stage-capacity relation, weather records, and other information are used to supplement base data in determining the daily flow or volume of water in storage. Records of stage are obtained from a water-stage recorder that is either downloaded electronically in the field to a laptop computer or similar device or is transmitted using telemetry such as GOES satellite, land-line or cellular-phone modems, or by radio transmission. Measurements of discharge are made with a current meter or acoustic Doppler current profiler, using the general methods adopted by the USGS. These methods are described in standard textbooks, USGS Water-Supply Paper 2175, and the Techniques of Water-Resources Investigations of the United States Geological Survey (TWRIs), Book 3, Chapters A1 through A19 and Book 8, Chapters A2 and B2. The methods are consistent with the American Society for Testing and Materials (ASTM) standards and generally follow the standards of the International Organization for Standards (ISO). For stream-gaging stations, discharge-rating tables for any stage are prepared from stage-discharge curves. If extensions to the rating curves are necessary to express discharge greater than measured, the extensions are made on the basis of indirect measurements of peak discharge (such as slope-area or contracted-opening measurements, or computation of flow over dams and weirs), step-backwater techniques, velocity-area studies, and logarithmic plotting. The daily mean discharge is computed from gage heights and rating tables, then the monthly and yearly mean discharges are computed from the daily values. If the stage-discharge relation is subject to change because of frequent or continual change in the physical features of the stream channel, the daily mean discharge is computed 134 132 131 27 74 16 COORDINATES FOR WELLS 27 (180150066474900) AND 74 (180135066471000) COORDINATES FOR WELLS 132 (180133066503300) AND 134 (180120066503200) COORDINATES FOR WELLS 131 (180058066502700) COORDINATES FOR WELLS 16 (175922066495800) 20 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 by the shifting-control method in which correction factors based on individual discharge measurements and notes by engineers and observers are used when applying the gage heights to the rating tables. If the stage-discharge relation for a station is temporarily changed by the presence of aquatic growth or debris on the controlling section, the daily mean discharge is computed by the shifting-control method. The stage-discharge relation at some stream-gaging stations is affected by backwater from reservoirs, tributary streams, or other sources. Such an occurrence necessitates the use of the slope method in which the slope or fall in a reach of the stream is a factor in computing discharge. The slope or fall is obtained by means of an auxiliary gage at some distance from the base gage. An index velocity is measured using ultrasonic or acoustic instruments at some stream-gaging stations and this index velocity is used to calculate an average velocity for the flow in the stream. This average velocity along with a stage-area relation is then used to calculate average discharge. At some stations, stage-discharge relation is affected by changing stage. At these stations, the rate of change in stage is used as a factor in computing discharge. At some stream-gaging stations in the northern United States, the stage-discharge relation is affected by ice in the winter; therefore, computation of the discharge in the usual manner is impossible. Discharge for periods of ice effect is computed on the basis of gage-height record and occasional winter-discharge measurements. Consideration is given to the available information on temperature and precipitation, notes by gage observers and hydrologists, and comparable records of discharge from other stations in the same or nearby basins. For a lake or reservoir station, capacity tables giving the volume or contents for any stage are prepared from stage-area relation curves defined by surveys. The application of the stage to the capacity table gives the contents, from which the daily, monthly, or yearly changes are computed. If the stage-capacity curve is subject to changes because of deposition of sediment in the reservoir, periodic resurveys of the reservoir are necessary to define new stage-capacity curves. During the period between reservoir surveys, the computed contents may be increasingly in error due to the gradual accumulation of sediment. For some stream-gaging stations, periods of time occur when no gage-height record is obtained or the recorded gage height is faulty and cannot be used to compute daily discharge or contents. Such a situation can happen when the recorder stops or otherwise fails to operate properly, the intakes are plugged, the float is frozen in the well, or for various other reasons. For such periods, the daily discharges are estimated on the basis of recorded range in stage, prior and subsequent records, discharge measurements, weather records, and comparison with records from other stations in the same or nearby basins. Likewise, lake or reservoir volumes may be estimated on the basis of operator’s log, prior and subsequent records, inflow-outflow studies, and other information. Data Presentation The records published for each continuous-record surface-water discharge station (stream-gaging station) consist of five parts: (1) the station manuscript or description; (2) the data table of daily mean values of discharge for the current water year with summary data; (3) a tabular statistical summary of monthly mean flow data for a designated period, by water year; (4) a summary statistics table that includes statistical data of annual, daily, and instantaneous flows as well as data pertaining to annual runoff, 7-day low-flow minimums, and flow duration; and (5) a hydrograph of discharge. 21 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Station Manuscript The manuscript provides, under various headings, descriptive information, such as station location; period of record; historical extremes outside the period of record; record accuracy; and other remarks pertinent to station operation and regulation. The following information, as appropriate, is provided with each continuous record of discharge or lake content. Comments follow that clarify information presented under the various headings of the station description. LOCATION.—Location information is obtained from the most accurate maps available. The location of the gaging station with respect to the cultural and physical features in the vicinity and with respect to the reference place mentioned in the station name is given. River mileages, given for only a few stations, were determined by methods given in “River Mileage Measurement,” Bulletin 14, Revision of October 1968, prepared by the Water Resources Council or were provided by the U.S. Army Corps of Engineers. DRAINAGE AREA.—Drainage areas are measured using the most accurate maps available. Because the type of maps available varies from one drainage basin to another, the accuracy of drainage areas likewise varies. Drainage areas are updated as better maps become available. PERIOD OF RECORD.—This term indicates the time period for which records have been published for the station or for an equivalent station. An equivalent station is one that was in operation at a time that the present station was not and whose location was such that its flow reasonably can be considered equivalent to flow at the present station. REVISED RECORDS.—If a critical error in published records is discovered, a revision is included in the first report published following discovery of the error. GAGE.—The type of gage in current use, the datum of the current gage referred to a standard datum, and a condensed history of the types, locations, and datums of previous gages are given under this heading. REMARKS.—All periods of estimated daily discharge either will be identified by date in this paragraph of the station description for water-discharge stations or flagged in the daily discharge table. (See section titled Identifying Estimated Daily Discharge.) Information is presented relative to the accuracy of the records, to special methods of computation, and to conditions that affect natural flow at the station. In addition, information may be presented pertaining to average discharge data for the period of record; to extremes data for the period of record and the current year; and, possibly, to other pertinent items. For reservoir stations, information is given on the dam forming the reservoir, the capacity, the outlet works and spillway, and the purpose and use of the reservoir. COOPERATION.—Records provided by a cooperating organization or obtained for the USGS by a cooperating organization are identified here. EXTREMES OUTSIDE PERIOD OF RECORD.—Information here documents major floods or unusually low flows that occurred outside the stated period of record. The information may or may not have been obtained by the USGS. REVISIONS.—Records are revised if errors in published records are discovered. Appropriate updates are made in the USGS distributed data system, NWIS, and subsequently to its Web-based National data system, NWISWeb (http://water.usgs.gov/nwis/nwis). Users are encouraged to obtain all required data from NWIS or NWISWeb to ensure that they have the most recent data updates. Updates to NWISWeb are made on an annual basis. 22 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Although rare, occasionally the records of a discontinued gaging station may need revision. Because no current or, possibly, future station manuscript would be published for these stations to document the revision in a REVISED RECORDS entry, users of data for these stations who obtained the record from previously published data reports may wish to contact the District Office (address given on the back of the title page of this report) to determine if the published records were revised after the station was discontinued. If, however, the data for a discontinued station were obtained by computer retrieval, the data would be current. Any published revision of data is always accompanied by revision of the corresponding data in computer storage. Manuscript information for lake or reservoir stations differs from that for stream stations in the nature of the REMARKS and in the inclusion of a stage-capacity table when daily volumes are given. Data Table of Daily Mean Values The daily table of discharge records for stream-gaging stations gives mean discharge for each day of the water year. In the monthly summary for the table, the line headed TOTAL gives the sum of the daily figures for each month; the line headed MEAN gives the arithmetic average flow in cubic feet per second for the month; and the lines headed MAX and MIN give the maximum and minimum daily mean discharges, respectively, for each month. Discharge for the month is expressed in cubic feet per second per square mile (line headed CFSM); or in inches (line headed IN); or in acre-feet (line headed AC-FT). Values for cubic feet per second per square mile and runoff in inches or in acre-feet may be omitted if extensive regulation or diversion is in effect or if the drainage area includes large noncontributing areas. At some stations, monthly and (or) yearly observed discharges are adjusted for reservoir storage or diversion, or diversion data or reservoir volumes are given. These values are identified by a symbol and a corresponding footnote. Statistics of Monthly Mean Data A tabular summary of the mean (line headed MEAN), maximum (MAX), and minimum (MIN) of monthly mean flows for each month for a designated period is provided below the mean values table. The water years of the first occurrence of the maximum and minimum monthly flows are provided immediately below those values. The designated period will be expressed as FOR WATER YEARS __-__, BY WATER YEAR (WY), and will list the first and last water years of the range of years selected from the PERIOD OF RECORD paragraph in the station manuscript. The designated period will consist of all of the station record within the specified water years, including complete months of record for partial water years, and may coincide with the period of record for the station. The water years for which the statistics are computed are consecutive, unless a break in the station record is indicated in the manuscript. Summary Statistics A table titled SUMMARY STATISTICS follows the statistics of monthly mean data tabulation. This table consists of four columns with the first column containing the line headings of the statistics being reported. The table provides a statistical summary of yearly, daily, and instantaneous flows, not only for the current water year but also for the previous calendar year and for a designated period, as appropriate. The designated period selected, WATER YEARS __-__, will consist of all of the station records within the specified water years, including complete months of record for partial water years, and may coincide with the period of record for the station. The water years for which the statistics are computed are consecutive, unless a break in the station record is indicated in the manuscript. All of the calculations for the statistical characteristics designated ANNUAL (see line headings below), except for the ANNUAL 7-DAY MINIMUM statistic, are calculated for the designated period using complete water years. The other statistical characteristics may be calculated using partial water years. 23 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 The date or water year, as appropriate, of the first occurrence of each statistic reporting extreme values of discharge is provided adjacent to the statistic. Repeated occurrences may be noted in the REMARKS paragraph of the manuscript or in footnotes. Because the designated period may not be the same as the station period of record published in the manuscript, occasionally the dates of occurrence listed for the daily and instantaneous extremes in the designated-period column may not be within the selected water years listed in the heading. When the dates of occurrence do not fall within the selected water years listed in the heading, it will be noted in the REMARKS paragraph or in footnotes. Selected streamflow duration-curve statistics and runoff data also are given. Runoff data may be omitted if extensive regulation or diversion of flow is in effect in the drainage basin. The following summary statistics data are provided with each continuous record of discharge. Comments that follow clarify information presented under the various line headings of the SUMMARY STATISTICS table. ANNUAL TOTAL.—The sum of the daily mean values of discharge for the year. ANNUAL MEAN.—The arithmetic mean for the individual daily mean discharges for the year noted or for the designated period. HIGHEST ANNUAL MEAN.—The maximum annual mean discharge occurring for the designated period. LOWEST ANNUAL MEAN.—The minimum annual mean discharge occurring for the designated period. HIGHEST DAILY MEAN.—The maximum daily mean discharge for the year or for the designated period. LOWEST DAILY MEAN.—The minimum daily mean discharge for the year or for the designated period. ANNUAL 7-DAY MINIMUM.—The lowest mean discharge for 7 consecutive days for a calendar year or a water year. Note that most low-flow frequency analyses of annual 7-day minimum flows use a climatic year (April 1 March 31). The date shown in the summary statistics table is the initial date of the 7-day period. This value should not be confused with the 7-day 10-year low-flow statistic. MAXIMUM PEAK FLOW.—The maximum instantaneous peak discharge occurring for the water year or designated period. Occasionally the maximum flow for a year may occur at midnight at the beginning or end of the year, on a recession from or rise toward a higher peak in the adjoining year. In this case, the maximum peak flow is given in the table and the maximum flow may be reported in a footnote or in the REMARKS paragraph in the manuscript. MAXIMUM PEAK STAGE.—The maximum instantaneous peak stage occurring for the water year or designated period. Occasionally the maximum stage for a year may occur at midnight at the beginning or end of the year, on a recession from or rise toward a higher peak in the adjoining year. In this case, the maximum peak stage is given in the table and the maximum stage may be reported in the REMARKS paragraph in the manuscript or in a footnote. If the dates of occurrence of the maximum peak stage and maximum peak flow are different, the REMARKS paragraph in the manuscript or a footnote may be used to provide further information. INSTANTANEOUS LOW FLOW.—The minimum instantaneous discharge occurring for the water year or for the designated period. ANNUAL RUNOFF.—Indicates the total quantity of water in runoff for a drainage area for the year. Data reports may use any of the following units of measurement in presenting annual runoff data: Acre-foot (AC-FT) is the quantity of water required to cover 1 acre to a depth of 1 foot and is equivalent to 43,560 cubic feet or about 326,000 gallons or 1,233 cubic meters. 24 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Cubic feet per square mile (CFSM) is the average number of cubic feet of water flowing per second from each square mile of area drained, assuming the runoff is distributed uniformly in time and area. Inches (INCHES) indicate the depth to which the drainage area would be covered if all of the runoff for a given time period were uniformly distributed on it. 10 PERCENT EXCEEDS.—The discharge that has been exceeded 10 percent of the time for the designated period. 50 PERCENT EXCEEDS.—The discharge that has been exceeded 50 percent of the time for the designated period. 90 PERCENT EXCEEDS.—The discharge that has been exceeded 90 percent of the time for the designated period. Data collected at partial-record stations follow the information for continuous-record sites. Data for partial- record discharge stations are presented in two tables. The first table lists annual maximum stage and discharge at crest-stage stations, and the second table lists discharge measurements at low-flow partial-record stations. The tables of partial-record stations are followed by a listing of discharge measurements made at sites other than continuous-record or partial-record stations. These measurements are often made in times of drought or flood to give better areal coverage to those events. Those measurements and others collected for a special reason are called measurements at miscellaneous sites. Identifying Estimated Daily Discharge Estimated daily-discharge values published in the water-discharge tables of annual State data reports are identified. This identification is shown either by flagging individual daily values with the letter “e” and noting in a table footnote, “e–Estimated,” or by listing the dates of the estimated record in the REMARKS paragraph of the station description. Accuracy of Field Data and Computed Results The accuracy of streamflow data depends primarily on (1) the stability of the stage-discharge relation or, if the control is unstable, the frequency of discharge measurements, and (2) the accuracy of observations of stage, measurements of discharge, and interpretations of records. The degree of accuracy of the records is stated in the REMARKS in the station description. “Excellent” indicates that about 95 percent of the daily discharges are within 5 percent of the true value; “good” within 10 percent; and “fair,” within 15 percent. “Poor” indicates that daily discharges have less than “fair” accuracy. Different accuracies may be attributed to different parts of a given record. Values of daily mean discharge in this report are shown to the nearest hundredth of a cubic foot per second for discharges of less than 1 ft3/s; to the nearest tenths between 1.0 and 10 ft3/s; to whole numbers between 10 and 1,000 ft3/s; and to 3 significant figures above 1,000 ft3/s. The number of significant figures used is based solely on the magnitude of the discharge value. The same rounding rules apply to discharge values listed for partial-record stations. Discharge at many stations, as indicated by the monthly mean, may not reflect natural runoff due to the effects of diversion, consumption, regulation by storage, increase or decrease in evaporation due to artificial causes, or to other factors. For such stations, values of cubic feet per second per square mile and of runoff in inches are not published unless satisfactory adjustments can be made for diversions, for changes in contents of reservoirs, or for other changes incident to use and control. Evaporation from a reservoir is not included in the adjustments for changes in reservoir contents, unless it is so stated. Even at those stations where adjustments are made, large errors in computed runoff may occur if adjustments or losses are large in comparison with the observed discharge. 25 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Other Data Records Available Information of a more detailed nature than that published for most of the stream-gaging stations such as discharge measurements, gage-height records, and rating tables is available from the District office. Also, most stream-gaging station records are available in computer-usable form and many statistical analyses have been made. Information on the availability of unpublished data or statistical analyses may be obtained from the District office (see address that is shown on the back of the title page of this report). RECORDS OF SURFACE-WATER QUALITY Records of surface-water quality ordinarily are obtained at or near stream gaging stations because interpretation of records of surface-water quality nearly always requires corresponding discharge data. Records of surface-water quality in this report may involve a variety of types of data and measurement frequencies. Classification of Records Water-quality data for surface-water sites are grouped into one of three classifications. A continuing-record station is a site where data are collected on a regularly scheduled basis. Frequency may be once or more times daily, weekly, monthly, or quarterly. A partial-record station is a site where limited water-quality data are collected systematically over a period of years. Frequency of sampling is usually less than quarterly. A miscellaneous sampling site is a location other than a continuing or partial-record station, where random samples are collected to give better areal coverage to define water-quality conditions in the river basin. A careful distinction needs to be made between "continuing records" as used in this report and "continuous recordings," which refers to a continuous graph or a series of discrete values punched at short intervals on a paper tape. Some records of water quality, such as temperature and specific conductance, may be obtained through continuous recordings; however, because of costs, most data are obtained only monthly or less frequently. Locations of stations for which records on the quality of surface water appear in this report are shown in figure 6. Arrangement of Records Water-quality records collected at a surface-water daily record station are published immediately following that record, regardless of the frequency of sample collection. Station number and name are the same for both records. Where a surface-water daily record station is not available or where the water quality differs significantly from that at the nearby surface-water station, the continuing water-quality record is published with its own station number and name in the regular downstream-order sequence. Water-quality data for partial-record stations and for miscellaneous sampling sites appear in separate tables following the table of discharge measurement at miscellaneous sites. On-site Measurements and Sample Collection In obtaining water-quality data, a major concern needs to be assuring that the data obtained represent the in situ quality of the water. To assure this, certain measurements, such as water temperature, pH, and dissolved oxygen, need to be made onsite when the samples are taken. To assure that measurements made in the laboratory also represent the in situ water, carefully prescribed procedures need to be followed in collecting the samples, in treating the samples to prevent changes in quality pending analysis, and in shipping the samples to the laboratory. Procedures for onsite measurements and for collecting, treating, and shipping samples are given in publications on "Techniques of Water-Resources Investigations," Book 1, Chap. D2; Book 3, Chap. C2; Book 5, Chap. A1, A3, and A4. Detailed information on collecting, treating, and shipping samples may be obtained from the Geological Survey District office. 26 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 One sample can define adequately the water quality at a given time if the mixture of solutes throughout the stream cross section is homogeneous. However, the concentration of solutes at different locations in the cross section may vary widely with different rates of water discharge, depending on the source of material and the turbulence and mixing of the stream. Some streams must be sampled through several vertical sections to obtain a representative sample needed for an accurate mean concentration and for use in calculating load. Whether samples are obtained from the centroid of flow or from several verticals, depends on flow conditions and other factors which must be evaluated by the collector. Chemical-quality data published in this report are considered to be the most representative values available for the stations listed. The values reported represent water-quality conditions at the time of sampling as much as possible, consistent with available sampling techniques and methods of analysis. In the rare case where an apparent inconsistency exists between a reported pH value and the relative abundance of carbon dioxide species (carbonate and bicarbonate), the inconsistency is the result of a slight uptake of carbon dioxide from the air by the sample between measurement of pH in the field and determination of carbonate and bicarbonate in the laboratory. Water Temperature Water temperatures are measured at most of the water-quality stations. In addition, water temperatures are taken at time of discharge measurements for water-discharge stations. Large streams have a small diurnal temperature change; shallow streams may have a daily range of several degrees and may follow closely the changes in air temperature. Some streams may be affected by waste-heat discharges. Water temperatures measured at the time of water-discharge measurements are on file in the District office. Sediment Suspended-sediment concentrations are determined from samples collected by using depth-integrating and pumping sediment samplers. Samples usually are obtained at several verticals in the cross section, or a single sample may be obtained at a fixed point and a coefficient applied to determine the mean concentration in the cross sections. During periods of rapidly changing flow or rapidly changing concentration, samples may have been collected more frequently (twice daily or hourly). The published sediment discharges for days of rapidly changing flow or concentration were computed by the subdivided-day method (time-discharge weighted average). For periods when no samples were collected, daily discharges of suspended sediment were estimated on the basis of water discharge, sediment concentrations observed immediately before and after the periods, suspended-sediment loads for other periods of similar discharge, and computed by the subdivided-day method using the transport curves. At other stations, suspended-sediment samples were collected periodically at many verticals in the stream cross section. Although data collected periodically may represent conditions only at the time of observations, such data are useful in establishing seasonal relations between quality and streamflow and in predicting long-term sediment- discharge characteristics of the stream. In addition to the records of suspended-sediment discharge, records of the periodic measurements of the particle-size distribution of the suspended sediment are included for some stations. 27 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Laboratory Measurements Samples for indicator bacteria are analyzed in the mobile laboratories immediately after collection. Sediment samples are analyzed in the U.S. Geological Survey laboratories in the Kentucky District Sediment Laboratory. All other samples are analyzed in the Geological Survey laboratories in Denver, Co. or Ocala, Fla. Methods used in analyzing sediment samples and computing sediment records are given in TWRI, Book 5, Chap. C1. Methods used by the Geological Survey laboratories are given in TWRI, Book 1, Chap. D2; Book 3, Chap. C2; Book 5, Chap. A1, A3, and A4. Data Presentation For continuing-record stations, information pertinent to the history of station operation is provided in descriptive headings preceding the tabular data. These descriptive headings give details regarding location, drainage area, period of record, type of data available, instrumentation, general remarks, cooperation, and extremes for parameters currently measured daily. Tables of chemical, physical, biological, radiochemical data, and so forth, obtained at a frequency less than daily are presented first, and tables of "daily values" of suspended sediment then follow in sequence. In the descriptive headings, if the location is identical to that of the discharge gaging station, neither the LOCATION nor the DRAINAGE AREA statements are repeated. The following information, as appropriate, is provided with each continuous-record station. Comments that follow clarify information presented under the various headings of the station description. LOCATION.--See Data Presentation under "Records of Stage and Water Discharge;" same comments apply. DRAINAGE AREA.--See Data Presentation under "Records of Stage and Water Discharge;" same comments apply. PERIOD OF RECORD.--This indicates the periods for which there are published water-quality records for the station. The periods are shown separately for records of parameters measured daily or continuously and those measured less than daily. For those measured daily or continuously, periods of record are given for the parameters individually. INSTRUMENTATION.--Information on instrumentation is given only if a water-quality monitor temperature record, sediment pumping sampler, or other sampling device is in operation at a station. REMARKS.--Remarks provide added information pertinent to the collection, analysis, or computation of the records. COOPERATION.--Records provided by a cooperating organization or obtained for the Geological Survey by a cooperating organization are identified here. EXTREMES.--Maximums and minimums are given only for parameters measured daily or more frequently. None are given for parameters measured weekly or less frequently, because the true maximums or minimums may not have been sampled. Extremes, when given, are provided for both the period of record and for the current water year. 28 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 REVISIONS.--If errors in published water-quality records are discovered after publication, appropriate updates are made to the Water-Quality File in the U.S. Geological Survey's computerized data system, WATSTORE, and subsequently by monthly transfer of update transactions to the U.S. Environmental Protection Agency's STORET system. Because the usual volume of updates makes it impractical to document individual changes in the State data-report series or elsewhere, potential users of U.S. Geological Survey water-quality data are encouraged to obtain all required data from the appropriate computer file to insure the most recent updates. The surface-water-quality records for partial-record stations and miscellaneous sampling sites are published in separate tables following the table of discharge measurements at miscellaneous sites. No descriptive statements are given for these records. Each station is published with its own station number and name in the regular downstream- order sequence. Remark Codes The following remark codes may appear with the water-quality data in this section: Printed Output Remark E or e Estimated value. > Actual value is known to be greater than the value shown. < Actual value is known to be less than the value shown. M Presence verified, not quantified RECORDS OF GROUND-WATER LEVELS Only ground-water level data from a basic network of observation wells are published herein. This basic network contains observation wells so located that the most significant data are obtained from the fewest wells in the most important aquifers. Data Collection and Computation Measurements of water levels are made in many types of wells under varying conditions, but the methods of measurement are standardized to the extent possible. The equipment and measuring techniques used at each observation well ensure that measurements at each well are of consistent accuracy and reliability. Each well is identified by means of (1) a 15-digit number that is based on latitude and longitude and (2) a local number that is provided for easy reference. See figure 9. Water-level records are obtained from direct measurements with a steel tape at about monthly intervals at all observation wells and also from digital water-stage data logger at 60-minute intervals at selected wells. The water- level measurements in this report are given in feet with reference to land-surface datum (lsd). Land-surface datum is a datum plane that is approximately at land surface at each well. If known, the elevation of the land-surface datum is given in the well description. The height of the measuring point (MP) above or below land-surface datum is given in each well description. Water levels in wells equipped with recording gages are reported for every day and as an instantaneous observation at noon. Water levels are reported to as many significant figures as can be justified by the local conditions. For example, in a measurement of a depth to water of several hundred feet, the error of determining the absolute value of the total depth to water may be a few tenths of a foot, whereas the error in determining the net change of water level between successive measurements may be only a hundredth of a few hundredths of a foot. For lesser depths to water, the accuracy is greater. Accordingly, most measurements reported to a hundredth of a foot. 29 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Data Presentation Each well record consists of three parts, the station description, the data table of water levels observed during the water year and a graph of the water levels for the current water year and other selected period. The description of the well is presented first through use of descriptive headings preceding the tabular data. The comments to follow clarify information presented under the various headings of the well description. LOCATION.--This paragraph follows the well-identification number and reports the latitude and longitude (given in degrees, minutes, and seconds); a landline location designation; the hydrologic-unit number; the distance and direction from a geographic point of reference; and the observation well name. AQUIFER.--This entry designates by name (if a name exists) and geologic unit open to the well. WELL CHARACTERISTICS.--This entry describes the well in terms of depth, diameter, casing depth and/or screened interval, method of construction, use, and additional information such as casing breaks, collapsed screen, and other changes since construction. INSTRUMENTATION.--This paragraph provides information on both the frequency of measurement and the collection method used, allowing the user to better evaluate the reported water-level extremes by knowing whether they are based on weekly, monthly, or some other frequency of measurement. DATUM.--This entry describes both the measuring point and the land-surface elevation at the well. The measuring point is described physically (such as top of collar, notch in top of casing, plug in pump base and so on), and in relation to land surface (such as 1.3 ft above land-surface datum). The elevation of the land-surface datum is described in feet above (or below) sea level; it is reported with a precision depending on the method of determination. REMARKS.--This entry describes factors that may influence the water level in a well or the measurement of the water level. It should identify wells that also are water-quality observation wells, and may be used to acknowledge the assistance of local (non-Survey) observers. PERIOD OF RECORD.--This entry indicates the period for which there are published records for the well. It reports the month and year of the start of publication of water-level records by the U.S. Geological Survey and the words "to current year" if the records are to be continued into the following year. Periods for which water-level records are available, but are not published by the Geological Survey, may be noted. EXTREMES FOR PERIOD OF RECORD.--This entry contains the highest and lowest water levels of the period of published record, with respect to land-surface datum, and the dates of their occurrence. Water-Level Tables A table of water levels follows the station description for each well. Water levels are reported in feet below land-surface datum and all taped measurements of water level are listed. For wells equipped with recorders, daily values tables are published for the instantaneous water-level observation at noon. The highest and lowest water levels of the water year and their dates of occurrence are shown on a line below the table. Because all values are not published for wells with data loggers, the extremes may be values that are not listed in the table. Missing records are indicated by dashes in place of the water level. A hydrograph for a selected period of record follows each water-level table. 30 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 ACCESS TO U.S. GEOLOGICAL SURVEY WATER DATA The U.S. Geological Survey provides near real-time stage and discharge data for many of the gaging stations equipped with the necessary telemetry and historic daily-mean and peak-flow discharge data for most current or discontinued gaging stations through the world wide web (WWW). These data may be accessed at http:// water.usgs.gov. Water-quality data and ground-water data also are available through the WWW. In addition, data can be provided in various machine-readable formats on various media. Information about the availability of specific types of data or products, and user charges, can be obtained locally from each Water Discipline District Office (See address that is shown on the back of the title page of this report.) 31 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 DEFINITION OF TERMS Specialized technical terms related to streamflow, water-quality, and other hydrologic data, as used in this report, are defined below. Terms such as algae, water level, and precipitation are used in their common everyday meanings, definitions of which are given in standard dictionaries. Not all terms defined in this alphabetical list apply to every State. See also table for converting English units to International System (SI) Units. Other glossaries that also define water-related terms are accessible from http:/ /water.usgs.gov/glossaries.html. Acid neutralizing capacity (ANC) is the equivalent sum of all bases or base-producing materials, solutes plus particulates, in an aqueous system that can be titrated with acid to an equivalence point. This term designates titration of an “unfiltered” sample (formerly reported as alkalinity). Acre-foot (AC-FT, acre-ft) is a unit of volume, commonly used to measure quantities of water used or stored, equivalent to the volume of water required to cover 1 acre to a depth of 1 foot and equivalent to 43,560 cubic feet, 325,851 gallons, or 1,233 cubic meters. (See also “Annual runoff”) Adenosine triphosphate (ATP) is an organic, phosphate-rich compound important in the transfer of energy in organisms. Its central role in living cells makes ATP an excellent indicator of the presence of living material in water. A measurement of ATP therefore provides a sensitive and rapid estimate of biomass. ATP is reported in micrograms per liter. Adjusted discharge is discharge data that have been mathematically adjusted (for example, to remove the effects of a daily tide cycle or reservoir storage). Algal growth potential (AGP) is the maximum algal dry weight biomass that can be produced in a natural water sample under standardized laboratory conditions. The growth potential is the algal biomass present at stationary phase and is expressed as milligrams dry weight of algae produced per liter of sample. (See also “Biomass” and “Dry weight”) Alkalinity is the capacity of solutes in an aqueous system to neutralize acid. This term designates titration of a “filtered” sample. Annual runoff is the total quantity of water that is discharged (“runs off”) from a drainage basin in a year. Data reports may present annual runoff data as volumes in acre-feet, as discharges per unit of drainage area in cubic feet per second per square mile, or as depths of water on the drainage basin in inches. Annual 7-day minimum is the lowest mean value for any 7-consecutive-day period in a year. Annual 7-day minimum values are reported herein for the calendar year and the water year (October 1 through September 30). Most low-flow frequency analyses use a climatic year (April 1-March 31), which tends to prevent the low-flow period from being artificially split between adjacent years. The date shown in the summary statistics table is the initial date of the 7-day period. (This value should not be confused with the 7-day, 10-year low-flow statistic.) Aroclor is the registered trademark for a group of poly-chlorinated biphenyls that were manufactured by the Monsanto Company prior to 1976. Aroclors are assigned specific 4-digit reference numbers dependent upon molecular type and degree of substitution of the biphenyl ring hydrogen atoms by chlorine atoms. The first two digits of a numbered aroclor represent the molecular type, and the last two digits represent the percentage weight of the hydrogen-substituted chlorine. Artificial substrate is a device that purposely is placed in a stream or lake for colonization of organisms. The artificial substrate simplifies the community structure by standardizing the substrate from which each sample is collected. Examples of artificial substrates are basket samplers (made of wire cages filled with clean streamside rocks) and multiplate samplers (made of hardboard) for benthic organism collection, and plexiglass strips for periphyton collection. (See also “Substrate”) Ash mass is the mass or amount of residue present after the residue from a dry-mass determination has been ashed in a muffle furnace at a temperature of 500 ºC for 1 hour. Ash mass of zooplankton and phytoplankton is expressed in grams per cubic meter (g/m3), and periphyton and benthic organisms in grams per square meter (g/m2). (See also “Biomass” and “Dry mass”) Aspect is the direction toward which a slope faces with respect to the compass. 32 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Bacteria are microscopic unicellular organisms, typically spherical, rodlike, or spiral and threadlike in shape, often clumped into colonies. Some bacteria cause disease, whereas others perform an essential role in nature in the recycling of materials; for example, by decomposing organic matter into a form available for reuse by plants. Bankfull stage, as used in this report, is the stage at which a stream first overflows its natural banks formed by floods with 1- to 3-year recurrence intervals. Base discharge (for peak discharge) is a discharge value, determined for selected stations, above which peak discharge data are published. The base discharge at each station is selected so that an average of about three peak flows per year will be published. (See also “Peak flow”) Base flow is sustained flow of a stream in the absence of direct runoff. It includes natural and human-induced streamflows. Natural base flow is sustained largely by ground-water discharge. Bed material is the sediment mixture of which a stream-bed, lake, pond, reservoir, or estuary bottom is composed. (See also “Bedload” and “Sediment”) Bedload is material in transport that primarily is supported by the streambed. In this report, bedload is considered to consist of particles in transit from the bed to the top of the bedload sampler nozzle (an elevation ranging from 0.25 to 0.5 foot). These particles are retained in the bedload sampler. A sample collected with a pressure-differential bedload sampler also may contain a component of the suspended load. Bedload discharge (tons per day) is the rate of sediment moving as bedload, reported as dry weight, that passes through a cross section in a given time. NOTE: Bedload discharge values in this report may include a component of the suspended- sediment discharge. A correction may be necessary when computing the total sediment discharge by summing the bedload discharge and the suspended-sediment discharge. (See also “Bedload,” “Dry weight,” “Sediment,” and “Suspended sediment discharge”) Benthic organisms are the group of organisms inhabiting the bottom of an aquatic environment. They include a number of types of organisms, such as bacteria, fungi, insect larvae and nymphs, snails, clams, and crayfish. They are useful as indicators of water quality. Biochemical oxygen demand (BOD) is a measure of the quantity of dissolved oxygen, in milligrams per liter, necessary for the decomposition of organic matter by microorganisms, such as bacteria. Biomass is the amount of living matter present at any given time, expressed as mass per unit area or volume of habitat. Biomass pigment ratio is an indicator of the total proportion of periphyton that are autotrophic (plants). This also is called the Autotrophic Index. Blue-green algae (Cyanophyta) are a group of phytoplankton and periphyton organisms with a blue pigment in addition to a green pigment called chlorophyll. Blue-green algae can cause nuisance water-quality conditions in lakes and slow-flowing rivers; however, they are found commonly in streams throughout the year. The abundance of blue-green algae in phytoplankton samples is expressed as the number of cells per milliliter (cells/mL) or biovolume in cubic micrometers per milliliter (P m3/mL). The abundance of blue-green algae in periphyton samples is given in cells per square centimeter (cells/ cm2) or biovolume per square centimeter (P m3/cm2). See also “Phytoplankton”and “Periphyton”) Bottom material (See “Bed material”) Bulk electrical conductivity is the combined electrical conductivity of all material within a doughnut-shaped volume surrounding an induction probe. Bulk conductivity is affected by different physical and chemical properties of the material including the dissolved-solids content of the pore water, and the lithology and porosity of the rock. Canadian Geodetic Vertical Datum 1928 is a geodetic datum derived from a general adjustment of Canada’s first order level network in 1928. 33 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Cell volume (biovolume) determination is one of several common methods used to estimate biomass of algae in aquatic systems. Cell members of algae are used frequently in aquatic surveys as an indicator of algal production. However, cell numbers alone cannot represent true biomass because of considerable cell-size variation among the algal species. Cell volume (P m3) is determined by obtaining critical cell measurements or cell dimensions (for example, length, width, height, or radius) for 20 to 50 cells of each important species to obtain an average biovolume per cell. Cells are categorized according to the correspondence of their cellular shape to the nearest geometric solid or combinations of simple solids (for example, spheres, cones, or cylinders). Representative formulae used to compute biovolume are as follows: sphere 4/3 Sr3 cone 1/3 Sr2h cylinder Sr2h. pi (S is the ratio of the circumference to the diameter of a circle; pi = 3.14159…. From cell volume, total algal biomass expressed as biovolume (P m3/mL) is thus determined by multiplying the number of cells of a given species by its average cell volume and then summing these volumes for all species. Cells/volume refers to the number of cells of any organism that is counted by using a microscope and grid or counting cell. Many planktonic organisms are multicelled and are counted according to the number of contained cells per sample volume, and generally are reported as cells or units per milliliter (mL) or liter (L). Cfs-day (See “Cubic foot per second-day”) Channel bars, as used in this report, are the lowest prominent geomorphic features higher than the channel bed. Chemical oxygen demand (COD) is a measure of the chemically oxidizable material in the water and furnishes an approximation of the amount of organic and reducing material present. The determined value may correlate with BOD or with carbonaceous organic pollution from sewage or industrial wastes. [See also “Biochemical oxygen demand (BOD)”] Clostridium perfringens (C. perfringens) is a spore-forming bacterium that is common in the feces of human and other warmblooded animals. Clostridial spores are being used experimentally as an indicator of past fecal contamination and the presence of microorganisms that are resistant to disinfection and environmental stresses. (See also “Bacteria”) Coliphages are viruses that infect and replicate in coliform bacteria. They are indicative of sewage contamination of water and of the survival and transport of viruses in the environment. Color unit is produced by 1 milligram per liter of platinum in the form of the chloroplatinate ion. Color is expressed in units of the platinum-cobalt scale. Confined aquifer is a term used to describe an aquifer containing water between two relatively impermeable bound-aries. The water level in a well tapping a confined aquifer stands above the top of the confined aquifer and can be higher or lower than the water table that may be present in the material above it. In some cases, the water level can rise above the ground surface, yielding a flowing well. Contents is the volume of water in a reservoir or lake. Unless otherwise indicated, volume is computed on the basis of a level pool and does not include bank storage. Continuous-record station is a site where data are collected with sufficient frequency to define daily mean values and variations within a day. Control designates a feature in the channel that physically affects the water-surface elevation and thereby determines the stage-discharge relation at the gage. This feature may be a constriction of the channel, a bedrock outcrop, a gravel bar, an artificial structure, or a uniform cross section over a long reach of the channel. Control structure, as used in this report, is a structure on a stream or canal that is used to regulate the flow or stage of the stream or to prevent the intrusion of saltwater. 34 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Cubic foot per second (CFS, ft3/s) is the rate of discharge representing a volume of 1 cubic foot passing a given point in 1 second. It is equivalent to approximately 7.48 gallons per second or approximately 449 gallons per minute, or 0.02832 cubic meters per second. The term “second-foot” sometimes is used synonymously with “cubic foot per second” but is now obsolete. Cubic foot per second-day (CFS-DAY, Cfs-day, [(ft3/s)/d]) is the volume of water represented by a flow of 1cubic foot per second for 24 hours. It is equivalent to 86,400cubic feet, 1.98347 acre-feet, 646,317 gallons, or 2,446.6 cubic meters. The daily mean discharges reported in the daily value data tables numerically are equal to the daily volumes in cfs-days, and the totals also represent volumes in cfs-days. Cubic foot per second per square mile [CFSM, (ft3/s)/mi2] is the average number of cubic feet of water flowing per second from each square mile of area drained, assuming the runoff is distributed uniformly in time and area. (See also “Annual runoff”) Daily mean suspended-sediment concentration is the time-weighted mean concentration of suspended sediment passing a stream cross section during a 24-hour day. (See also “Sediment” and “Suspended-sediment concentration”) Daily record station is a site where data are collected with sufficient frequency to develop a record of one or more data values per day. The frequency of data collection can range from continuous recording to data collection on a daily or near-daily basis. Data collection platform (DCP) is an electronic instrument that collects, processes, and stores data from various sensors, and transmits the data by satellite data relay, line-of-sight radio, and/or landline telemetry. Data logger is a microprocessor-based data acquisition system designed specifically to acquire, process, and store data. Data usually are downloaded from onsite data loggers for entry into office data systems. Datum is a surface or point relative to which measurements of height and/or horizontal position are reported. A vertical datum is a horizontal surface used as the zero point for measurements of gage height, stage, or elevation; a horizontal datum is a reference for positions given in terms of latitude-longitude, State Plane coordinates, or Universal Transverse Mercator (UTM) coordinates. (See also “Gage datum,” “Land-surface datum,” “National Geodetic Vertical Datum of 1929,” and “North American Vertical Datum of 1988”) Diatoms (Bacillariophyta) are unicellular or colonial algae with a siliceous cell wall. The abundance of diatoms in phytoplankton samples is expressed as the number of cells per milliliter (cells/mL) or biovolume in cubic micrometers per milliliter (P m3/mL). The abundance of diatoms in periphyton samples is given in cells per square centimeter (cells/cm 2) or biovolume per square centimeter (P m3/cm2). (See also “Phytoplankton” and “Periphyton”) Diel is of or pertaining to a 24-hour period of time; a regular daily cycle. Discharge, or flow, is the rate that matter passes through a cross section of a stream channel or other water body per unit of time. The term commonly refers to the volume of water (including, unless otherwise stated, any sediment or other constituents suspended or dissolved in the water) that passes a cross section in a stream channel, canal, pipeline, and so forth, within a given period of time (cubic feet per second). Discharge also can apply to the rate at which constituents, such as suspended sediment, bedload, and dissolved or suspended chemicals, pass through a cross section, in which cases the quantity is expressed as the mass of constituent that passes the cross section in a given period of time (tons per day). Dissolved refers to that material in a representative water sample that passes through a 0.45-micrometer membrane filter. This is a convenient operational definition used by Federal and State agencies that collect water-quality data. Determinations of “dissolved” constituent concentrations are made on sample water that has been filtered. Dissolved oxygen (DO) is the molecular oxygen (oxygen gas) dissolved in water. The concentration in water is a function of atmospheric pressure, temperature, and dissolved-solids concentration of the water. The ability of water to retain oxygen decreases with increasing temperature or dissolved-solids concentration. Photosynthesis and respiration by plants commonly cause diurnal variations in dissolved-oxygen concentration in water from some streams. 35 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Dissolved solids concentration in water is the quantity of dissolved material in a sample of water. It is determined either analytically by the “residue-on-evaporation” method, or mathematically by totaling the concentrations of individual constituents reported in a comprehensive chemical analysis. During the analytical determination, the bicarbonate (generally a major dissolved component of water) is converted to carbonate. In the mathematical calculation, the bicarbonate value, in milligrams per liter, is multiplied by 0.4926 to convert it to carbonate. Alternatively, alkalinity concentration (as mg/L CaCO3) can be converted to carbonate concentration by multiplying by 0.60. Diversity index (H) (Shannon index) is a numerical expression of evenness of distribution of aquatic organisms. The formula for diversity index is: s ni ni d = – ¦ ----log2----, n n i | 1 where ni is the number of individuals per taxon, n is the total number of individuals, and s is the total number of taxa in the sample of the community. Index values range from zero, when all the organisms in the sample are the same, to some positive number, when some or all of the organisms in the sample are different. Drainage area of a stream at a specific location is that area upstream from the location, measured in a horizontal plane, that has a common outlet at the site for its surface runoff from precipitation that normally drains by gravity into a stream. Drainage areas given herein include all closed basins, or noncontributing areas, within the area unless otherwise specified. Drainage basin is a part of the Earth’s surface that contains a drainage system with a common outlet for its surface runoff. (See “Drainage area”) Dry mass refers to the mass of residue present after drying in an oven at 105 qC, until the mass remains unchanged. This mass represents the total organic matter, ash and sediment, in the sample. Dry-mass values are expressed in the same units as ash mass. (See also “Ash mass,” “Biomass,” and “Wet mass”) Dry weight refers to the weight of animal tissue after it has been dried in an oven at 65 °C until a constant weight is achieved. Dry weight represents total organic and inorganic matter in the tissue. (See also “Wet weight”) Embeddedness is the degree to which gravel-sized and larger particles are surrounded or enclosed by finer-sized particles. (See also “Substrate embeddedness class”) Enterococcus bacteria commonly are found in the feces of humans and other warmblooded animals. Although some strains are ubiquitous and not related to fecal pollution, the presence of enterococci in water is an indication of fecal pollution and the possible presence of enteric pathogens. Enterococcus bacteria are those bacteria that produce pink to red colonies with black or reddish-brown precipitate after incubation at 41 qC on mE agar (nutrient medium for bacterial growth) and subsequent transfer to EIA medium. Enterococci include Streptococcus feacalis, Streptococcus feacium, Streptococcus avium, and their variants. (See also “Bacteria”) EPT Index is the total number of distinct taxa within the insect orders Ephemeroptera, Plecoptera, and Trichoptera. This index summarizes the taxa richness within the aquatic insects that generally are considered pollution sensitive; the index usually decreases with pollution. Escherichia coli (E. coli) are bacteria present in the intestine and feces of warmblooded animals. E. coli are a member species of the fecal coliform group of indicator bacteria. In the laboratory, they are defined as those bacteria that produce yellow or yellow-brown colonies on a filter pad saturated with urea substrate broth after primary culturing for 22 to 24 hours at 44.5 °C on mTEC medium (nutrient medium for bacterial growth). Their concentrations are expressed as number of colonies per 100 mL of sample. (See also “Bacteria”) 36 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Estimated (E) value of a concentration is reported when an analyte is detected and all criteria for a positive result are met. If the concentration is less than the method detection limit (MDL), an E code will be reported with the value. If the analyte is identified qualitatively as present, but the quantitative determination is substantially more uncertain, the National Water Quality Laboratory will identify the result with an E code even though the measured value is greater than the MDL. A value reported with an E code should be used with caution. When no analyte is detected in a sample, the default reporting value is the MDL preceded by a less than sign (<). For bacteriological data, concentrations are reported as estimated when results are based on non-ideal colony counts. Euglenoids (Euglenophyta) are a group of algae that usually are free-swimming and rarely creeping. They have the ability to grow either photosynthetically in the light or heterotrophically in the dark. (See also “Phytoplankton”) Extractable organic halides (EOX) are organic compounds that contain halogen atoms such as chlorine. These organic compounds are semivolatile and extractable by ethyl acetate from air-dried streambed sediment. The ethyl acetate extract is combusted, and the concentration is determined by microcoulometric determination of the halides formed. The concentration is reported as micrograms of chlorine per gram of the dry weight of the streambed sediment. Fecal coliform bacteria are present in the intestines or feces of warmblooded animals. They often are used as indicators of the sanitary quality of the water. In the laboratory, they are defined as all organisms that produce blue colonies within 24 hours when incubated at 44.5qC plus or minus 0.2 qC on M-FC medium (nutrient medium for bacterial growth). Their concentrations are expressed as number of colonies per 100 mL of sample. (See also “Bacteria”) Fecal streptococcal bacteria are present in the intestines of warmblooded animals and are ubiquitous in the environment. They are characterized as gram-positive, cocci bacteria that are capable of growth in brain-heart infusion broth. In the laboratory, they are defined as all the organisms that produce red or pink colonies within 48 hours at 35 qC plus or minus 1.0 qC on KF-streptococcus medium (nutrient medium for bacterial growth). Their concentrations are expressed as number of colonies per 100 mL of sample. (See also “Bacteria”) Fire algae (Pyrrhophyta) are free-swimming unicells characterized by a red pigment spot. (See also “Phytoplankton”) Flow-duration percentiles are values on a scale of 100 that indicate the percentage of time for which a flow is not exceeded. For example, the 90th percentile of river flow is greater than or equal to 90 percent of all recorded flow rates. Gage datum is a horizontal surface used as a zero point for measurement of stage or gage height. This surface usually is located slightly below the lowest point of the stream bottom such that the gage height is usually slightly greater than the maximum depth of water. Because the gage datum is not an actual physical object, the datum is usually defined by specifying the elevations of permanent reference marks such as bridge abutments and survey monuments, and the gage is set to agree with the reference marks. Gage datum is a local datum that is maintained independently of any national geodetic datum. However, if the elevation of the gage datum relative to the national datum (North American Vertical Datum of 1988 or National Geodetic Vertical Datum of 1929) has been determined, then the gage readings can be converted to elevations above the national datum by adding the elevation of the gage datum to the gage reading. Gage height (G.H.) is the water-surface elevation, in feet above the gage datum. If the water surface is below the gage datum, the gage height is negative. Gage height often is used interchangeably with the more general term “stage,” although gage height is more appropriate when used in reference to a reading on a gage. Gage values are values that are recorded, transmitted, and/or computed from a gaging station. Gage values typically are collected at 5-, 15-, or 30-minute intervals. Gaging station is a site on a stream, canal, lake, or reservoir where systematic observations of stage, discharge, or other hydrologic data are obtained. Gas chromatography/flame ionization detector (GC/FID) is a laboratory analytical method used as a screening technique for semivolatile organic compounds that are extractable from water in methylene chloride. Geomorphic channel units, as used in this report, are fluvial geomorphic descriptors of channel shape and stream velocity. Pools, riffles, and runs are types of geomorphic channel units considered for National Water-Quality Assessment (NAWQA) Program habitat sampling. 37 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Green algae (Chlorophyta) are unicellular or colonial algae with chlorophyll pigments similar to those in terrestrial green plants. Some forms of green algae produce mats or floating “moss” in lakes. The abundance of green algae in phytoplankton samples is expressed as the number of cells per milliliter (cells/mL) or biovolume in cubic micrometers per milliliter (P m3/ mL). The abundance of green algae in periphyton samples is given in cells per square centimeter (cells/cm 2) or biovolume per square centimeter (P m3/cm2). (See also “Phytoplankton” and “Periphyton”) Habitat, as used in this report, includes all nonliving (physical) aspects of the aquatic ecosystem, although living components like aquatic macrophytes and riparian vegetation also are usually included. Measurements of habitat typically are made over a wider geographic scale than are measurements of species distribution. Habitat quality index is the qualitative description (level 1) of instream habitat and riparian conditions surrounding the reach sampled. Scores range from 0 to 100 percent with higher scores indicative of desirable habitat conditions for aquatic life. Index only applicable to wadable streams. Hardness of water is a physical-chemical characteristic that commonly is recognized by the increased quantity of soap required to produce lather. It is computed as the sum of equivalents of polyvalent cations (primarily calcium and magnesium) and is expressed as the equivalent concentration of calcium carbonate (CaCO3). High tide is the maximum height reached by each rising tide. The high-high and low-high tides are the higher and lower of the two high tides, respectively, of each tidal day. See NOAA Web site: http://www.co-ops.nos.noaa.gov/tideglos.html Hilsenhoff’s Biotic Index (HBI) is an indicator of organic pollution that uses tolerance values to weight taxa abundances; usually increases with pollution. It is calculated as follows: n a H B I s u m---------------, = N where n is the number of individuals of each taxon, a is the tolerance value of each taxon, and N is the total number of organisms in the sample. Horizontal datum (See “Datum”) Hydrologic index stations referred to in this report are continuous-record gaging stations that have been selected as representative of streamflow patterns for their respective regions. Station locations are shown on index maps. Hydrologic unit is a geographic area representing part or all of a surface drainage basin or distinct hydrologic feature as defined by the former Office of Water Data Coordination and delineated on the State Hydrologic Unit Maps by the USGS. Each hydrologic unit is identified by an 8-digit number. Inch (IN., in.), in reference to streamflow, as used in this report, refers to the depth to which the drainage area would be covered with water if all of the runoff for a given time period were distributed uniformly on it. (See also “Annual runoff”) Instantaneous discharge is the discharge at a particular instant of time. (See also “Discharge”) International Boundary Commission Survey Datum refers to a geodetic datum established at numerous monuments along the United States-Canada boundary by the International Boundary Commission. Island, as used in this report, is a mid-channel bar that has permanent woody vegetation, is flooded once a year, on average, and remains stable except during large flood events. 38 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Laboratory reporting level (LRL) generally is equal to twice the yearly determined long-term method detection level (LT MDL). The LRL controls false negative error. The probability of falsely reporting a nondetection for a sample that contained an analyte at a concentration equal to or greater than the LRL is predicted to be less than or equal to 1 percent. The value of the LRL will be reported with a “less than” (<) remark code for samples in which the analyte was not detected. The National Water Quality Laboratory (NWQL) collects quality-control data from selected analytical methods on a continuing basis to determine LT-MDLs and to establish LRLs. These values are reevaluated annually on the basis of the most current quality- control data and, therefore, may change. The LRL replaces the term ‘non-detection value’ (NDV). Land-surface datum (lsd) is a datum plane that is approximately at land surface at each ground-water observation well. Latent heat flux (often used interchangeably with latent heat-flux density) is the amount of heat energy that converts water from liquid to vapor (evaporation) or from vapor to liquid (condensation) across a specified cross-sectional area per unit time. Usually expressed in watts per square meter. Light-attenuation coefficient, also known as the extinction coefficient, is a measure of water clarity. Light is attenuated according to the Lambert-Beer equation: –O L I I e , = o where Io is the source light intensity, I is the light intensity at length L (in meters) from the source, O is the light-attenuation coefficient, and e is the base of the natural logarithm. The light-attenuation coefficient is defined as 1 I O = –---loge----. L Io Lipid is any one of a family of compounds that are insoluble in water and that make up one of the principal components of living cells. Lipids include fats, oils, waxes, and steroids. Many environmental contaminants such as organochlorine pesticides are lipophilic. Long-term method detection level (LT-MDL) is a detection level derived by determining the standard deviation of a minimum of 24 method detection limit (MDL) spike-sample measurements over an extended period of time. LT-MDL data are collected on a continuous basis to assess year-to-year variations in the LT-MDL. The LT-MDL controls false positive error. The chance of falsely reporting a concentration at or greater than the LT-MDL for a sample that did not contain the analyte is predicted to be less than or equal to 1 percent. Low tide is the minimum height reached by each falling tide. The high-low and low-low tides are the higher and lower of the two low tides, respectively, of each tidal day. See NOAA Web site: http://www.co-ops.nos.noaa.gov/tideglos.html Macrophytes are the macroscopic plants in the aquatic environment. The most common macrophytes are the rooted vascular plants that usually are arranged in zones in aquatic ecosystems and restricted in the area by the extent of illumination through the water and sediment deposition along the shoreline. Mean concentration of suspended sediment (Daily mean suspended-sediment concentration) is the time-weighted concentration of suspended sediment passing a stream cross section during a given time period. (See also “Daily mean suspended-sediment concentration” and “Suspended-sediment concentration”) Mean discharge (MEAN) is the arithmetic mean of individual daily mean discharges during a specific period. (See also “Discharge”) Mean high or low tide is the average of all high or low tides, respectively, over a specific period. Mean sea level is a local tidal datum. It is the arithmetic mean of hourly heights observed over the National Tidal Datum Epoch. Shorter series are specified in the name; for example, monthly mean sea level and yearly mean sea level. In order that they may be recovered when needed, such datums are referenced to fixed points known as benchmarks. (See also “Datum”) 39 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Measuring point (MP) is an arbitrary permanent reference point from which the distance to water surface in a well is measured to obtain water level. Megahertz is a unit of frequency. One megahertz equals one million cycles per second. Membrane filter is a thin microporous material of specific pore size used to filter bacteria, algae, and other very small particles from water. Metamorphic stage refers to the stage of development that an organism exhibits during its transformation from an immature form to an adult form. This developmental process exists for most insects, and the degree of difference from the immature stage to the adult form varies from relatively slight to pronounced, with many intermediates. Examples of metamorphic stages of insects are egg-larva-adult or egg-nymph-adult. Method detection limit (MDL) is the minimum concentration of a substance that can be measured and reported with 99 percent confidence that the analyte concentration is greater than zero. It is determined from the analysis of a sample in a given matrix containing the analyte. At the MDL concentration, the risk of a false positive is predicted to be less than or equal to 1 percent. Method of Cubatures is a method of computing discharge in tidal estuaries based on the conservation of mass equation. Methylene blue active substances (MBAS) indicate the presence of detergents (anionic surfactants). The determination depends on the formation of a blue color when methylene blue dye reacts with synthetic anionic detergent compounds. Micrograms per gram (UG/G, P g/g) is a unit expressing the concentration of a chemical constituent as the mass (micrograms) of the element per unit mass (gram) of material analyzed. Micrograms per kilogram (UG/KG, P g/kg) is a unit expressing the concentration of a chemical constituent as the mass (micrograms) of the constituent per unit mass (kilogram) of the material analyzed. One microgram per kilogram is equivalent to 1 part per billion. Micrograms per liter (UG/L, P g/L) is a unit expressing the concentration of chemical constituents in water as mass (micrograms) of constituent per unit volume (liter) of water. One thousand micrograms per liter is equivalent to 1milligram per liter. One microgram per liter is equivalent to 1 part per billion. Microsiemens per centimeter (US/CM, P S/cm) is a unit expressing the amount of electrical conductivity of a solution as measured between opposite faces of a centimeter cube of solution at a specified temperature. Siemens is the International System of Units nomenclature. It is synonymous with mhos and is the reciprocal of resistance in ohms. Milligrams per liter (MG/L, mg/L) is a unit for expressing the concentration of chemical constituents in water as the mass (milligrams) of constituent per unit volume (liter) of water. Concentration of suspended sediment also is expressed in milligrams per liter and is based on the mass of dry sediment per liter of water-sediment mixture. Minimum reporting level (MRL) is the smallest measured concentration of a constituent that may be reliably reported by using a given analytical method. Miscellaneous site, miscellaneous station, or miscellaneous sampling site is a site where streamflow, sediment, and/or water- quality data or water-quality or sediment samples are collected once, or more often on a random or discontinuous basis to provide better areal coverage for defining hydrologic and water-quality conditions over a broad area in a river basin. Most probable number (MPN) is an index of the number of coliform bacteria that, more probably than any other number, would give the results shown by the laboratory examination; it is not an actual enumeration. MPN is determined from the distribution of gas-positive cultures among multiple inoculated tubes. Multiple-plate samplers are artificial substrates of known surface area used for obtaining benthic invertebrate samples. They consist of a series of spaced, hardboard plates on an eyebolt. 40 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Nanograms per liter (NG/L, ng/L) is a unit expressing the concentration of chemical constituents in solution as mass (nanograms) of solute per unit volume (liter) of water. One million nanograms per liter is equivalent to 1milligram per liter. National Geodetic Vertical Datum of 1929 (NGVD 29) is a fixed reference adopted as a standard geodetic datum for elevations determined by leveling. It formerly was called “Sea Level Datum of 1929” or “mean sea level.” Although the datum was derived from the mean sea level at 26 tide stations, it does not necessarily represent local mean sea level at any particular place. See NOAA Web site: http://www.ngs.noaa.gov/faq.shtml#WhatVD29VD88 (See “North American Vertical Datum of 1988”) Natural substrate refers to any naturally occurring immersed or submersed solid surface, such as a rock or tree, upon which an organism lives. (See also “Substrate”) Nekton are the consumers in the aquatic environment and consist of large, free-swimming organisms that are capable of sustained, directed mobility. Nephelometric turbidity unit (NTU) is the measurement for reporting turbidity that is based on use of a standard suspension of formazin. Turbidity measured in NTU uses nephelometric methods that depend on passing specific light of a specific wavelength through the sample. North American Datum of 1927 (NAD 27) is the horizontal control datum for the United States that was defined by a location and azimuth on the Clarke spheroid of 1866. North American Datum of 1983 (NAD 83) is the horizontal control datum for the United States, Canada, Mexico, and Central America that is based on the adjustment of 250,000 points including 600 satellite Doppler stations that constrain the system to a geocentric origin. NAD 83 has been officially adopted as the legal horizontal datum for the United States by the Federal government. North American Vertical Datum of 1988 (NAVD 88) is a fixed reference adopted as the official civilian vertical datum for elevations determined by Federal surveying and mapping activities in the United States. This datum was established in 1991 by minimum-constraint adjustment of the Canadian, Mexican, and United States first-order terrestrial leveling networks. Open or screened interval is the length of unscreened opening or of well screen through which water enters a well, in feet below land surface. Organic carbon (OC) is a measure of organic matter present in aqueous solution, suspension, or bottom sediment. May be reported as dissolved organic carbon (DOC), particulate organic carbon (POC), or total organic carbon (TOC). Organic mass or volatile mass of a living substance is the difference between the dry mass and ash mass and represents the actual mass of the living matter. Organic mass is expressed in the same units as for ash mass and dry mass. (See also “Ash mass,” “Biomass,” and “Dry mass”) Organism count/area refers to the number of organisms collected and enumerated in a sample and adjusted to the number per area habitat, usually square meter (m2), acre, or hectare. Periphyton, benthic organisms, and macrophytes are expressed in these terms. Organism count/volume refers to the number of organisms collected and enumerated in a sample and adjusted to the number per sample volume, usually milliliter (mL) or liter (L). Numbers of planktonic organisms can be expressed in these terms. Organochlorine compounds are any chemicals that contain carbon and chlorine. Organochlorine compounds that are important in investigations of water, sediment, and biological quality include certain pesticides and industrial compounds. Parameter code is a 5-digit number used in the USGS computerized data system, National Water Information System (NWIS), to uniquely identify a specific constituent or property. Partial-record station is a site where discrete measurements of one or more hydrologic parameters are obtained over a period of time without continuous data being recorded or computed. A common example is a crest-stage gage partial-record station at which only peak stages and flows are recorded. 41 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Particle size is the diameter, in millimeters (mm), of a particle determined by sieve or sedimentation methods. The sedimentation method uses the principle of Stokes Law to calculate sediment particle sizes. Sedimentation methods (pipet, bottom-withdrawal tube, visual-accumulation tube, sedigraph) determine fall diameter of particles in either distilled water (chemically dispersed) or in native water (the river water at the time and point of sampling). Particle-size classification, as used in this report, agrees with the recommendation made by the American Geophysical Union Subcommittee on Sediment Terminology. The classification is as follows: Classification Size (mm) Method of analysis Clay >0.00024 - 0.004 Sedimentation Silt >0.004 - 0.062 Sedimentation Sand >0.062 - 2.0 Sedimentation/sieve Gravel >2.0 - 64.0 Sieve Cobble >64 - 256 Manual measurement Boulder >256 Manual measurement The particle-size distributions given in this report are not necessarily representative of all particles in transport in the stream. For the sedimentation method, most of the organic matter is removed, and the sample is subjected to mechanical and chemical dispersion before analysis in distilled water. Chemical dispersion is not used for native water analysis. Peak flow (peak stage) is an instantaneous local maximum value in the continuous time series of streamflows or stages, preceded by a period of increasing values and followed by a period of decreasing values. Several peak values ordinarily occur in a year. The maximum peak value in a year is called the annual peak; peaks lower than the annual peak are called secondary peaks. Occasionally, the annual peak may not be the maximum value for the year; in such cases, the maximum value occurs at midnight at the beginning or end of the year, on the recession from or rise toward a higher peak in the adjoining year. If values are recorded at a discrete series of times, the peak recorded value may be taken as an approximation of the true peak, which may occur between the recording instants. If the values are recorded with finite precision, a sequence of equal recorded values may occur at the peak; in this case, the first value is taken as the peak. Percent composition or percent of total is a unit for expressing the ratio of a particular part of a sample or population to the total sample or population, in terms of types, numbers, weight, mass, or volume. Percent shading is a measure of the amount of sunlight potentially reaching the stream. A clinometer is used to measure left and right bank canopy angles. These values are added together, divided by 180, and multiplied by 100 to compute percentage of shade. Periodic-record station is a site where stage, discharge, sediment, chemical, physical, or other hydrologic measurements are made one or more times during a year but at a frequency insufficient to develop a daily record. Periphyton is the assemblage of microorganisms attached to and living upon submerged solid surfaces. Although primarily consisting of algae, they also include bacteria, fungi, protozoa, rotifers, and other small organisms. Periphyton are useful indicators of water quality. Pesticides are chemical compounds used to control undesirable organisms. Major categories of pesticides include insecticides, miticides, fungicides, herbicides, and rodenticides. pH of water is the negative logarithm of the hydrogen-ion activity. Solutions with pH less than 7.0 standard units are termed “acidic,” and solutions with a pH greater than 7.0 are termed “basic.” Solutions with a pH of 7.0 are neutral. The presence and concentration of many dissolved chemical constituents found in water are affected, in part, by the hydrogen-ion activity of water. Biological processes including growth, distribution of organisms, and toxicity of the water to organisms also are affected, in part, by the hydrogen-ion activity of water. 42 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Phytoplankton is the plant part of the plankton. They usually are microscopic, and their movement is subject to the water currents. Phytoplankton growth is dependent upon solar radiation and nutrient substances. Because they are able to incorporate as well as release materials to the surrounding water, the phytoplankton have a profound effect upon the quality of the water. They are the primary food producers in the aquatic environment and commonly are known as algae. (See also “Plankton”) Picocurie (PC, pCi) is one-trillionth (1 x 10-12) of the amount of radioactive nuclide represented by a curie (Ci). A curie is the quantity of radioactive nuclide that yields 3.7 x 1010 radioactive disintegrations per second (dps). A picocurie yields 0.037 dps, or 2.22 dpm (disintegrations per minute). Plankton is the community of suspended, floating, or weakly swimming organisms that live in the open water of lakes and rivers. Concentrations are expressed as a number of cells per milliliter (cells/mL) of sample. Polychlorinated biphenyls (PCBs) are industrial chemicals that are mixtures of chlorinated biphenyl compounds having various percentages of chlorine. They are similar in structure to organochlorine insecticides. Polychlorinated naphthalenes (PCNs) are industrial chemicals that are mixtures of chlorinated naphthalene compounds. They have properties and applications similar to polychlorinated biphenyls (PCBs) and have been identified in commercial PCB preparations. Pool, as used in this report, is a small part of a stream reach with little velocity, commonly with water deeper than surrounding areas. Primary productivity is a measure of the rate at which new organic matter is formed and accumulated through photo synthetic and chemosynthetic activity of producer organisms (chiefly, green plants). The rate of primary production is estimated by measuring the amount of oxygen released (oxygen method) or the amount of carbon assimilated (carbon method) by the plants. Primary productivity (carbon method) is expressed as milligrams of carbon per area per unit time [mg C/(m2/time)] for periphyton and macrophytes or per volume [mg C/(m3/time)] for phytoplankton. The carbon method defines the amount of carbon dioxide consumed as measured by radioactive carbon (carbon-14). The carbon-14 method is of greater sensitivity than the oxygen light- and dark-bottle method and is preferred for use with unenriched water samples. Unit time may be either the hour or day, depending on the incubation period. (See also “Primary productivity”) Primary productivity (oxygen method) is expressed as milligrams of oxygen per area per unit time [mgO/(m2/time)] for periphyton and macrophytes or per volume [mg O/(m3/time)] for phytoplankton. The oxygen method defines production and respiration rates as estimated from changes in the measured dissolved-oxygen concentration. The oxygen light- and dark- bottle method is preferred if the rate of primary production is sufficient for accurate measurements to be made within 24 hours. Unit time may be either the hour or day, depending on the incubation period. (See also “Primary productivity”) Radioisotopes are isotopic forms of elements that exhibit radioactivity. Isotopes are varieties of a chemical element that differ in atomic weight but are very nearly alike in chemical properties. The difference arises because the atoms of the isotopic forms of an element differ in the number of neutrons in the nucleus; for example, ordinary chlorine is a mixture of isotopes having atomic weights of 35 and 37, and the natural mixture has an atomic weight of about 35.453. Many of the elements similarly exist as mixtures of isotopes, and a great many new isotopes have been produced in the operation of nuclear devices such as the cyclotron. There are 275 isotopes of the 81 stable elements, in addition to more than 800 radioactive isotopes. Reach, as used in this report, is a length of stream that is chosen to represent a uniform set of physical, chemical, and biological conditions within a segment. It is the principal sampling unit for collecting physical, chemical, and biological data. 43 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Recoverable from bed (bottom) material is the amount of a given constituent that is in solution after a representative sample of bottom material has been digested by a method (usually using an acid or mixture of acids) that results in dissolution of readily soluble substances. Complete dissolution of all bottom material is not achieved by the digestion treatment and thus the determination represents less than the total amount (that is, less than 95 percent) of the constituent in the sample. To achieve comparability of analytical data, equivalent digestion procedures would be required of all laboratories performing such analyses because different digestion procedures are likely to produce different analytical results. (See also “Bed material”) Recurrence interval, also referred to as return period, is the average time, usually expressed in years, between occurrences of hydrologic events of a specified type (such as exceedances of a specified high flow or nonexceedance of a specified low flow). The terms “return period” and “recurrence interval” do not imply regular cyclic occurrence. The actual times between occurrences vary randomly, with most of the times being less than the average and a few being substantially greater than the average. For example, the 100-year flood is the flow rate that is exceeded by the annual maximum peak flow at intervals whose average length is 100 years (that is, once in 100 years, on average); almost two-thirds of all exceedances of the 100 year flood occur less than 100 years after the previous exceedance, half occur less than 70 years after the previous exceedance, and about one-eighth occur more than 200 years after the previous exceedance. Similarly, the 7-day, 10-year low flow (7Q10) is the flow rate below which the annual minimum 7-day-mean flow dips at intervals whose average length is 10 years (that is, once in 10years, on average); almost two-thirds of the nonexceedances of the 7Q10 occur less than 10 years after the previous nonexceedance, half occur less than 7years after, and about one-eighth occur more than 20 years after the previous nonexceedance. The recurrence interval for annual events is the reciprocal of the annual probability of occurrence. Thus, the 100-year flood has a 1-percent chance of being exceeded by the maximum peak flow in any year, and there is a 10 percent chance in any year that the annual minimum 7-day-mean flow will be less than the 7Q10. Replicate samples are a group of samples collected in a manner such that the samples are thought to be essentially identical in composition. Return period (See “Recurrence interval”) Riffle, as used in this report, is a shallow part of the stream where water flows swiftly over completely or partially submerged obstructions to produce surface agitation. River mileage is the curvilinear distance, in miles, measured upstream from the mouth along the meandering path of a stream channel in accordance with Bulletin No. 14 (October 1968) of the Water Resources Council and typically is used to denote location along a river. Run, as used in this report, is a relatively shallow part of a stream with moderate velocity and little or no surface turbulence. Runoff is the quantity of water that is discharged (“runs off”) from a drainage basin during a given time period. Runoff data may be presented as volumes in acre-feet, as mean discharges per unit of drainage area in cubic feet per second per square mile, or as depths of water on the drainage basin in inches. (See also “Annual runoff”) Sea level, as used in this report, refers to one of the two commonly used national vertical datums (NGVD 1929 or NAVD 1988). See separate entries for definitions of these datums. Sediment is solid material that originates mostly from disintegrated rocks; when transported by, suspended in, or deposited from water, it is referred to as “fluvial sediment.” Sediment includes chemical and biochemical precipitates and decomposed organic material, such as humus. The quantity, characteristics, and cause of the occurrence of sediment in streams are affected by environmental and land-use factors. Some major factors are topography, soil characteristics, land cover, and depth and intensity of precipitation. Sensible heat flux (often used interchangeably with latent sensible heat-flux density) is the amount of heat energy that moves by turbulent transport through the air across a specified cross-sectional area per unit time and goes to heating (cooling) the air. Usually expressed in watts per square meter. 44 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Seven-day, 10-year low flow (7Q10) is the discharge below which the annual 7-day minimum flow falls in 1 year out of 10 on the long-term average. The recurrence interval of the 7Q10 is 10 years; the chance that the annual 7-day minimum flow will be less than the 7Q10 is 10 percent in any given year. (See also “Annual 7-day minimum” and “Recurrence interval”) Shelves, as used in this report, are streambank features extending nearly horizontally from the flood plain to the lower limit of persistent woody vegetation. Sodium adsorption ratio (SAR) is the expression of relative activity of sodium ions in exchange reactions within soil and is an index of sodium or alkali hazard to the soil. Sodium hazard in water is an index that can be used to evaluate the suitability of water for irrigating crops. Soil heat flux (often used interchangeably with soil heat-flux density) is the amount of heat energy that moves by conduction across a specified cross-sectional area of soil per unit time and goes to heating (or cooling) the soil. Usually expressed in watts per square meter. Soil-water content is the water lost from the soil upon drying to constant mass at 105 qC; expressed either as mass of water per unit mass of dry soil or as the volume of water per unit bulk volume of soil. Specific electrical conductance (conductivity) is a measure of the capacity of water (or other media) to conduct an electrical current. It is expressed in microsiemens per centimeter at 25 qC. Specific electrical conductance is a function of the types and quantity of dissolved substances in water and can be used for approximating the dissolved-solids content of the water. Commonly, the concentration of dissolved solids (in milligrams per liter) is from 55 to 75percent of the specific conductance (in microsiemens). This relation is not constant from stream to stream, and it may vary in the same source with changes in the composition of the water. Stable isotope ratio (per MIL) is a unit expressing the ratio of the abundance of two radioactive isotopes. Isotope ratios are used in hydrologic studies to determine the age or source of specific water, to evaluate mixing of different water, as an aid in determining reaction rates, and other chemical or hydrologic processes. Stage (See “Gage height”) Stage-discharge relation is the relation between the water-surface elevation, termed stage (gage height), and the volume of water flowing in a channel per unit time. Streamflow is the discharge that occurs in a natural channel. Although the term “discharge” can be applied to the flow of a canal, the word “streamflow” uniquely describes the discharge in a surface stream course. The term “streamflow” is more general than “runoff” as streamflow may be applied to discharge whether or not it is affected by diversion or regulation. Substrate is the physical surface upon which an organism lives. Substrate embeddedness class is a visual estimate of riffle streambed substrate larger than gravel that is surrounded or covered by fine sediment (<2 mm, sand or finer). Below are the class categories expressed as the percentage covered by fine sediment: 0 no gravel or larger substrate 3 26-50 percent 1 > 75 percent 4 5-25 percent 2 51-75 percent 5 < 5 percent Surface area of a lake is that area (acres) encompassed by the boundary of the lake as shown on USGS topographic maps, or other available maps or photographs. Because surface area changes with lake stage, surface areas listed in this report represent those determined for the stage at the time the maps or photographs were obtained. Surficial bed material is the upper surface (0.1 to 0.2 foot) of the bed material that is sampled using U.S. Series Bed-Material Samplers. 45 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Surrogate is an analyte that behaves similarly to a target analyte, but that is highly unlikely to occur in a sample. A surrogate is added to a sample in known amounts before extraction and is measured with the same laboratory procedures used to measure the target analyte. Its purpose is to monitor method performance for an individual sample. Suspended (as used in tables of chemical analyses) refers to the amount (concentration) of undissolved material in a water- sediment mixture. It is defined operationally as the material retained on a 0.45-micrometer filter. Suspended, recoverable is the amount of a given constituent that is in solution after the part of a representative suspended water-sediment sample that is retained on a 0.45-micrometer membrane filter has been digested by a method (usually using a dilute acid solution) that results in dissolution of only readily soluble substances. Complete dissolution of all the particulate matter is not achieved by the digestion treatment, and, thus, the determination represents something less than the “total” amount (that is, less than 95percent) of the constituent present in the sample. To achieve comparability of analytical data, equivalent digestion procedures are required of all laboratories performing such analyses because different digestion procedures are likely to produce different analytical results. Determinations of “suspended, recoverable” constituents are made either by directly analyzing the suspended mate-rial collected on the filter or, more commonly, by difference, on the basis of determinations of (1) dissolved and (2) total recoverable concentrations of the constituent. (See also “Suspended”) Suspended sediment is the sediment maintained in suspension by the upward components of turbulent currents or that exists in suspension as a colloid. (See also “Sediment”) Suspended-sediment concentration is the velocity-weighted concentration of suspended sediment in the sampled zone (from the water surface to a point approximately 0.3 foot above the bed) expressed as milligrams of dry sediment per liter of water- sediment mixture (mg/L). The analytical technique uses the mass of all of the sediment and the net weight of the water- sediment mixture in a sample to compute the suspended-sediment concentration. (See also “Sediment” and “Suspended sediment”) Suspended-sediment discharge (tons/d) is the rate of sediment transport, as measured by dry mass or volume, that passes a cross section in a given time. It is calculated in units of tons per day as follows: concentration (mg/L) x discharge (ft3/s) x 0.0027. (See also “Sediment,” “Suspended sediment,” and “Suspended-sediment concentration”) Suspended-sediment load is a general term that refers to a given characteristic of the material in suspension that passes a point during a specified period of time. The term needs to be qualified, such as “annual suspended-sediment load” or “sand- size suspended-sediment load,” and so on. It is not synonymous with either suspended-sediment discharge or concentration. (See also “Sediment”) Suspended solids, total residue at 105 °C concentration is the concentration of inorganic and organic material retained on a filter, expressed as milligrams of dry material per liter of water (mg/L). An aliquot of the sample is used for this analysis. Suspended, total is the total amount of a given constituent in the part of a water-sediment sample that is retained on a 0.45- micrometer membrane filter. This term is used only when the analytical procedure assures measurement of at least 95 percent of the constituent determined. Knowledge of the expected form of the constituent in the sample, as well as the analytical methodology used, is required to determine when the results should be reported as “suspended, total.” Determinations of “suspended, total” constituents are made either by directly analyzing portions of the suspended material collected on the filter or, more commonly, by difference, on the basis of determinations of (1) dissolved and (2) total concentrations of the constituent. (See also “Suspended”) Synoptic studies are short-term investigations of specific water-quality conditions during selected seasonal or hydro-logic periods to provide improved spatial resolution for critical water-quality conditions. For the period and conditions sampled, they assess the spatial distribution of selected water-quality conditions in relation to causative factors, such as land use and contaminant sources. Taxa (Species) richness is the number of species (taxa) present in a defined area or sampling unit. 46 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Taxonomy is the division of biology concerned with the classification and naming of organisms. The classification of organisms is based upon a hierarchial scheme beginning with Kingdom and ending with Species at the base. The higher the classification level, the fewer features the organisms have in common. For example, the taxonomy of a particular mayfly, Hexagenia limbata, is the following: Kingdom: Animal Phylum: Arthropeda Class: Insecta Order: Ephemeroptera Family: Ephemeridae Genus: Hexagenia Species: Hexagenia limbata Thalweg is the line formed by connecting points of minimum streambed elevation (deepest part of the channel). Thermograph is an instrument that continuously records variations of temperature on a chart. The more general term “temperature recorder” is used in the table descriptions and refers to any instrument that records temperature whether on a chart, a tape, or any other medium. Time-weighted average is computed by multiplying the number of days in the sampling period by the concentrations of individual constituents for the corresponding period and dividing the sum of the products by the total number of days. A time-weighted average represents the composition of water resulting from the mixing of flow proportionally to the duration of the concentration. Tons per acre-foot (T/acre-ft) is the dry mass (tons) of a constituent per unit volume (acre-foot) of water. It is computed by multiplying the concentration of the constituent, in milligrams per liter, by 0.00136. Tons per day (T/DAY, tons/d) is a common chemical or sediment discharge unit. It is the quantity of a substance in solution, in suspension, or as bedload that passes a stream section during a 24-hour period. It is equivalent to 2,000 pounds per day, or 0.9072 metric ton per day. Total is the amount of a given constituent in a representative whole-water (unfiltered) sample, regardless of the constituent’s physical or chemical form. This term is used only when the analytical procedure assures measurement of at least 95 percent of the constituent present in both the dissolved and suspended phases of the sample. A knowledge of the expected form of the constituent in the sample, as well as the analytical methodology used, is required to judge when the results should be reported as “total.” (Note that the word “total” does double duty here, indicating both that the sample consists of a water- suspended sediment mixture and that the analytical method determined at least 95 percent of the constituent in the sample.) Total coliform bacteria are a particular group of bacteria that are used as indicators of possible sewage pollution. This group includes coliforms that inhabit the intestine of warmblooded animals and those that inhabit soils. They are characterized as aerobic or facultative anaerobic, gram-negative, nonspore-forming, rod-shaped bacteria that ferment lactose with gas formation within 48hours at 35 qC. In the laboratory, these bacteria are defined as all the organisms that produce colonies with a golden-green metallic sheen within 24 hours when incubated at 35 qC plus or minus 1.0 qC on M-Endo medium (nutrient medium for bacterial growth). Their concentrations are expressed as number of colonies per 100 milliliters of sample. (See also “Bacteria”) Total discharge is the quantity of a given constituent, measured as dry mass or volume, that passes a stream cross section per unit of time. When referring to constituents other than water, this term needs to be qualified, such as “total sediment discharge,” “total chloride discharge,” and so on. Total in bottom material is the amount of a given constituent in a representative sample of bottom material. This term is used only when the analytical procedure assures measurement of at least 95 percent of the constituent determined. A knowledge of the expected form of the constituent in the sample, as well as the analytical methodology used, is required to judge when the results should be reported as “total in bottom material.” 47 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Total length (fish) is the straight-line distance from the anterior point of a fish specimen’s snout, with the mouth closed, to the posterior end of the caudal (tail) fin, with the lobes of the caudal fin squeezed together. Total load refers to all of a constituent in transport. When referring to sediment, it includes suspended load plus bed load. Total organism count is the number of organisms collected and enumerated in any particular sample. (See also “Organism count/volume”) Total recoverable is the amount of a given constituent in a whole-water sample after a sample has been digested by a method (usually using a dilute acid solution) that results in dissolution of only readily soluble substances. Complete dissolution of all particulate matter is not achieved by the digestion treatment, and thus the determination represents something less than the “total” amount (that is, less than 95 percent) of the constituent present in the dissolved and suspended phases of the sample. To achieve comparability of analytical data for whole-water samples, equivalent digestion procedures are required of all laboratories performing such analyses because different digestion procedures may produce different analytical results. Total sediment discharge is the mass of suspended-sediment plus bed-load transport, measured as dry weight, that passes a cross section in a given time. It is a rate and is reported as tons per day. (See also “Bedload,” “Bedload discharge,” “Sediment,” “Suspended sediment,” and “Suspended-sediment concentration”) Total sediment load or total load is the sediment in transport as bedload and suspended-sediment load. The term may be qualified, such as “annual suspended-sediment load” or “sand-size suspended-sediment load,” and so on. It differs from total sediment discharge in that load refers to the material, whereas discharge refers to the quantity of material, expressed in units of mass per unit time. (See also “Sediment,” “Suspended-sediment load,” and “Total load”) Transect, as used in this report, is a line across a stream perpendicular to the flow and along which measurements are taken, so that morphological and flow characteristics along the line are described from bank to bank. Unlike a cross section, no attempt is made to determine known elevation points along the line. Turbidity is the reduction in the transparency of a solution because of the presence of suspended and some dissolved substances. The measurement technique records the collective optical properties of the solution that cause light to be scattered and attenuated rather than transmitted in straight lines; the higher the intensity of scattered or attenuated light, t he higher the value of the turbidity. Turbidity is expressed in nephelometric turbidity units (NTU). Depending on the method used, the turbidity units as NTU can be defined as the intensity of light of a specified wavelength scattered or attenuated by suspended particles or absorbed at a method specified angle, usually 90 degrees, from the path of the incident light. Currently approved methods for the measurement of turbidity in the USGS include those that conform to USEPA Method 180.1, ASTM D1889-00, and ISO 7027. Measurements of turbidity by these different methods and different instruments are unlikely to yield equivalent values. Ultraviolet (UV) absorbance (absorption) at 254 or 280nanometers is a measure of the aggregate concentration of the mixture of UV absorbing organic materials dissolved in the analyzed water, such as lignin, tannin, humic substances, and various aromatic compounds. UV absorbance (absorption) at 254 or 280 nanometers is measured in UV absorption units per centimeter of path length of UV light through a sample. Unconfined aquifer is an aquifer whose upper surface is a water table free to fluctuate under atmospheric pressure. (See “Water-table aquifer”) Vertical datum (See “Datum”) Volatile organic compounds (VOCs) are organic compounds that can be isolated from the water phase of a sample by purging the water sample with inert gas, such as helium, and, subsequently, analyzed by gas chromatography. Many VOCs are human-made chemicals that are used and produced in the manufacture of paints, adhesives, petroleum products, pharmaceuticals, and refrigerants. They often are components of fuels, solvents, hydraulic fluids, paint thinners, and dry- cleaning agents commonly used in urban settings. VOC contamination of drinking-water supplies is a human-health concern because many are toxic and are known or suspected human carcinogens. Water table is that surface in a ground-water body at which the water pressure is equal to the atmospheric pressure. 48 WATER RESOURCES DATA—PUERTO RICO AND THE U.S. VIRGIN ISLANDS, 2003 Water-table aquifer is an unconfined aquifer within which the water table is found. Water year in USGS reports dealing with surface-water supply is the 12-month period October 1 through September30. The water year is designated by the calendar year in which it ends and which includes 9 of the 12months. Thus, the year ending September 30, 2002, is called the “2002 water year.” Watershed (See “Drainage basin”) WDR is used as an abbreviation for “Water-Data Report” in the REVISED RECORDS paragraph to refer to State annual hydrologic-data reports. (WRD was used as an abbreviation for “Water-Resources Data” in reports published prior to 1976.) Weighted average is used in this report to indicate discharge-weighted average. It is computed by multiplying the discharge for a sampling period by the concentrations of individual constituents for the corresponding period and dividing the sum of the products by the sum of the discharges. A discharge-weighted average approximates the composition of water that would be found in a reservoir containing all the water passing a given location during the water year after thorough mixing in the reservoir. Wet mass is the mass of living matter plus contained water. (See also “Biomass” and “Dry mass”) Wet weight refers to the weight of animal tissue or other substance including its contained water. (See also “Dry weight”) WSP is used as an acronym for “Water-Supply Paper” in reference to previously published reports. Zooplankton is the animal part of the plankton. Zooplankton are capable of extensive movements within the water column and often are large enough to be seen with the unaided eye. Zooplankton are secondary consumers feeding upon bacteria, phytoplankton, and detritus. Because they are the grazers in the aquatic environment, the zooplankton are a vital part of the aquatic food web. The zooplankton community is dominated by small crustaceans and rotifers. (See also “Plankton”) 49 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS OF THE U.S. GEOLOGICAL SURVEY The USGS publishes a series of manuals, the Techniques of Water-Resources Investigations, describing procedures for planning and conducting specialized work in water-resources investigations. The material is grouped under major subject headings called books and is further divided into sections and chapters. For example, section A of book 3 (Applications of Hydraulics) pertains to surface water. The chapter, the unit of publication, is limited to a narrow field of subject matter. This format permits flexibility in revision and publication as the need arises. Reports in the Techniques of Water-Resources Investigations series, which are listed below, are online at http:/ /water.usgs.gov/pubs/twri/. Printed copies are for sale by the USGS, Information Services, Box 25286, Federal Center, Denver, Colorado 80225 (authorized agent of the Superintendent of Documents, Government Printing Office), telephone 1-888-ASK-USGS. Please telephone 1-888-ASK-USGS for current prices, and refer to the title, book number, chapter number, and mention the “U.S. Geological Survey Techniques of Water-Resources Investigations.” Products can then be ordered by telephone, or online at http://www.usgs.gov/sales.html, or by FAX to (303)236-469 of an order form available online at http://mac.usgs.gov/isb/pubs/forms/. Prepayment by major credit card or by a check or money order payable to the “U.S. Geological Survey” is required. Book 1. Collection of Water Data by Direct Measurement Section D. Water Quality 1-D1. Water temperature—influential factors, field measurement, and data presentation, by H.H.Stevens, Jr., J.F. Ficke, and G.F. Smoot: USGS–TWRI book 1, chap. D1. 1975. 65p. 1-D2. Guidelines for collection and field analysis of ground-water samples for selected unstable constituents, by W.W. Wood: USGS– TWRI book 1, chap. D2. 1976. 24 p. Book 2. Collection of Environmental Data Section D. Surface Geophysical Methods 2-D1. Application of surface geophysics to ground-water investigations, by A.A. R. Zohdy, G.P. Eaton, and D.R. Mabey: USGS–TWRI book 2, chap. D1. 1974. 116 p. 2-D2. Application of seismic-refraction techniques to hydrologic studies, by F.P. Haeni: USGS–TWRI book 2, chap. D2. 1988. 86 p. Section E. Subsurface Geophysical Methods 2-E1. Application of borehole geophysics to water-resources investigations, by W.S. Keys and L.M.MacCary: USGS–TWRI book 2, chap. E1. 1971. 126 p. 2-E2. Borehole geophysics applied to ground-water investigations, by W.S. Keys: USGS–TWRI book 2, chap. E2. 1990. 150 p. Section F. Drilling and Sampling Methods 2-F1. Application of drilling, coring, and sampling techniques to test holes and wells, by Eugene Shuter and W.E. Teasdale: USGS– TWRI book 2, chap. F1. 1989. 97 p. Book 3. Applications of Hydraulics Section A. Surface-Water Techniques 3-A1. General field and office procedures for indirect discharge measurements, by M.A. Benson and Tate Dalrymple: USGS–TWRI book 3, chap. A1. 1967. 30 p. 3-A2. Measurement of peak discharge by the slope-area method, by Tate Dalrymple and M.A. Benson: USGS–TWRI book 3, chap. A2. 1967. 12 p. 3-A3. Measurement of peak discharge at culverts by indirect methods, by G.L. Bodhaine: USGS–TWRI book 3, chap. A3. 1968. 60 p. 3-A4. Measurement of peak discharge at width contractions by indirect methods, by H.F. Matthai: USGS-TWRI book 3, chap. A4. 1967. 44 p. 3-A5. Measurement of peak discharge at dams by indirect methods, by Harry Hulsing: USGS–TWRI book 3. chap. A5. 1967. 29 p. 3-A6. General procedure for gaging streams, by R.W. Carter and Jacob Davidian: USGS–TWRI book 3, chap. A6. 1968. 13 p. 3-A7. Stage measurement at gaging stations, by T.J. Buchanan and W.P. Somers: USGS–TWRI book 3, chap. A7. 1968. 28 p. 3-A8. Discharge measurements at gaging stations, by T.J. Buchanan and W.P. Somers: USGS–TWRI book 3, chap. A8. 1969. 65 p. 50 3-A9. Measurement of time of travel in streams by dye tracing, by F.A. Kilpatrick and J.F. Wilson, Jr.: USGS–TWRI book 3, chap. A9. 1989. 27 p. 3-Al0. Discharge ratings at gaging stations, by E.J. Kennedy: USGS–TWRI book 3, chap. A10. 1984. 59 p. 3-A11. Measurement of discharge by the moving-boat method, by G.F. Smoot and C.E. Novak: USGS–TWRI book 3, chap. A11. 1969. 22 p. 3-A12. Fluorometric procedures for dye tracing, Revised, by J.F. Wilson, Jr., E.D. Cobb, and F.A. Kilpatrick: USGS–TWRI book 3, chap. A12. 1986. 34 p. 3-A13. Computation of continuous records of streamflow, by E.J. Kennedy: USGS–TWRI book 3, chap. A13. 1983. 53 p. 3-A14. Use of flumes in measuring discharge, by F.A. Kilpatrick and V.R. Schneider: USGS–TWRI book 3, chap. A14. 1983. 46 p. 3-A15. Computation of water-surface profiles in open channels, by Jacob Davidian: USGS–TWRI book 3, chap. A15. 1984. 48 p. 3-A16. Measurement of discharge using tracers, by F.A. Kilpatrick and E.D. Cobb: USGS–TWRI book 3, chap. A16. 1985. 52 p. 3-A17. Acoustic velocity meter systems, by Antonius Laenen: USGS–TWRI book 3, chap. A17. 1985. 38 p. 3-A18. Determination of stream reaeration coefficients by use of tracers, by F.A. Kilpatrick, R.E.Rathbun, Nobuhiro Yotsukura, G.W.Parker, and L.L. DeLong: USGS–TWRI book 3, chap. A18. 1989. 52 p. 3-A19. Levels at streamflow gaging stations, by E.J. Kennedy: USGS–TWRI book 3, chap. A19. 1990. 31 p. 3-A20. Simulation of soluble waste transport and buildup in surface waters using tracers, by F.A. Kilpatrick: USGS–TWRI book 3, chap. A20. 1993. 38 p. 3-A21 Stream-gaging cableways, by C. Russell Wagner: USGS–TWRI book 3, chap. A21. 1995. 56 p. Section B. Ground-Water Techniques 3-B1. Aquifer-test design, observation, and data analysis, by R.W. Stallman: USGS–TWRI book 3, chap. B1. 1971. 26 p. 3-B2. Introduction to ground-water hydraulics, a programed text for self-instruction, by G.D. Bennett: USGS–TWRI book 3, chap. B2. 1976. 172 p. 3-B3. Type curves for selected problems of flow to wells in confined aquifers, by J.E. Reed: USGS–TWRI book 3, chap. B3. 1980. 106 p. 3-B4. Regression modeling of ground-water flow, by R.L. Cooley and R.L. Naff: USGS–TWRI book 3, chap. B4. 1990. 232 p. 3-B4. Supplement 1. Regression modeling of ground-water flow --Modifications to the computer code for nonlinear regression solution of steady-state ground-water flow problems, by R.L. Cooley: USGS–TWRI book 3, chap. B4. 1993. 8 p. 3-B5. Definition of boundary and initial conditions in the analysis of saturated ground-water flow systems—An introduction, by O.L.Franke, T.E. Reilly, and G.D. Bennett: USGS–TWRI book 3, chap. B5. 1987. 15 p. 3-B6. The principle of superposition and its application in ground-water hydraulics, by T.E. Reilly, O.L.Franke, and G.D.Bennett: USGS–TWRI book 3, chap. B6. 1987. 28 p. 3-B7. Analytical solutions for one-, two-, and three-dimensional solute transport in ground-water systems with uniform flow, by E.J. Wexler: USGS–TWRI book 3, chap. B7. 1992. 190 p. 3-B8. System and boundary conceptualization in ground-water flow simulation, by T.E. Reilly: USGS–TWRI book 3, chap. B8. 2001. 29 p. Section C. Sedimentation and Erosion Techniques 3-C1. Fluvial sediment concepts, by H.P. Guy: USGS–TWRI book 3, chap. C1. 1970. 55 p. 3-C2. Field methods for measurement of fluvial sediment, by T.K. Edwards and G.D. Glysson: USGS–TWRI book 3, chap. C2. 1999. 89 p. 3-C3. Computation of fluvial-sediment discharge, by George Porterfield: USGS–TWRI book 3, chap.C3. 1972. 66 p. Book 4. Hydrologic Analysis and Interpretation Section A. Statistical Analysis 4-A1. Some statistical tools in hydrology, by H.C. Riggs: USGS–TWRI book 4, chap. A1. 1968. 39p. 4-A2. Frequency curves, by H.C. Riggs: USGS–TWRI book 4, chap. A2. 1968. 15 p. 4–A3. Statistical methods in water resources, by D.R. Helsel and R.M. Hirsch: USGS–TWRI book 4, chap. A3. 1991. Available only online at http://water.usgs.gov/pubs/twri/twri4a3/. (Accessed August 30, 2002.) Section B. Surface Water 4-B1. Low-flow investigations, by H.C. Riggs: USGS–TWRI book 4, chap. B1. 1972. 18 p. 4-B2. Storage analyses for water supply, by H.C. Riggs and C.H. Hardison: USGS–TWRI book 4, chap. B2. 1973. 20 p. 4-B3. Regional analyses of streamflow characteristics, by H.C. Riggs: USGS–TWRI book 4, chap.B3. 1973. 15 p. 51 Section D. Interrelated Phases of the Hydrologic Cycle 4-D1. Computation of rate and volume of stream depletion by wells, by C.T. Jenkins: USGS–TWRI book4, chap. D1. 1970. 17 p. Book 5. Laboratory Analysis Section A. Water Analysis 5-A1. Methods for determination of inorganic substances in water and fluvial sediments, by M.J.Fishman and L.C. Friedman, editors: USGS–TWRI book 5, chap. A1. 1989. 545 p. 5-A2. Determination of minor elements in water by emission spectroscopy, by P.R. Barnett and E.C.Mallory, Jr.: USGS– TWRI book 5, chap. A2. 1971. 31 p. 5-A3. Methods for the determination of organic substances in water and fluvial sediments, edited by R.L. Wershaw, M.J.Fishman, R.R. Grabbe, and L.E. Lowe: USGS–TWRI book 5, chap. A3. 1987. 80 p. 5-A4. Methods for collection and analysis of aquatic biological and microbiological samples, by L.J.Britton and P.E. Greeson, editors: USGS–TWRI book 5, chap. A4. 1989. 363 p. 5-A5. Methods for determination of radioactive substances in water and fluvial sediments, by L.L.Thatcher, V.J. Janzer, and K.W.Edwards: USGS–TWRI book 5, chap. A5. 1977. 95p. 5-A6. Quality assurance practices for the chemical and biological analyses of water and fluvial sediments, by L.C. Friedman and D.E. Erdmann: USGS–TWRI book 5, chap. A6. 1982. 181p. Section C. Sediment Analysis 5-C1. Laboratory theory and methods for sediment analysis, by H.P. Guy: USGS–TWRI book 5, chap.C1. 1969. 58 p. Book 6. Modeling Techniques Section A. Ground Water 6-A1. A modular three-dimensional finite-difference ground-water flow model, by M.G. McDonald and A.W. Harbaugh: USGS–TWRI book 6, chap. A1. 1988. 586 p. 6-A2. Documentation of a computer program to simulate aquifer-system compaction using the modular finite-difference ground-water flow model, by S.A. Leake and D.E. Prudic: USGS–TWRI book 6, chap. A2. 1991. 68 p. 6-A3. A modular finite-element model (MODFE) for areal and axisymmetric ground-water-flow problems, Part 1: Model Description and User’s Manual, by L.J. Torak: USGS–TWRI book 6, chap. A3. 1993. 136 p. 6-A4. A modular finite-element model (MODFE) for areal and axisymmetric ground-water-flow problems, Part 2: Derivation of finite-element equations and comparisons with analytical solutions, by R.L. Cooley: USGS–TWRI book 6, chap. A4. 1992. 108 p. 6-A5. A modular finite-element model (MODFE) for areal and axisymmetric ground-water-flow problems, Part 3: Design philosophy and programming details, by L.J. Torak: USGS–TWRI book 6, chap. A5, 1993. 243 p. 6-A6. A coupled surface-water and ground-water flow model (MODBRANCH) for simulation of stream-aquifer interaction, by Eric D. Swain and Eliezer J. Wexler: USGS–TWRI book 6, chap. A5,1996. 125 p. 6–A7. User’s guide to SEAWAT: A computer program for simulation of three-dimensional variable-density ground-water flow, by Weixing Guo and Christian D. Langevin: USGS–TWRI book 6, chap. A7. 2002. 77 p. Book 7. Automated Data Processing and Computations Section C. Computer Programs 7-C1. Finite difference model for aquifer simulation in two dimensions with results of numerical experiments, by P.C. Trescott, G.F.Pinder, and S.P. Larson: USGS–TWRI book 7, chap. C1. 1976. 116 p. 7-C2. Computer model of two-dimensional solute transport and dispersion in ground water, by L.F.Konikow and J.D.Bredehoeft: USGS–TWRI book 7, chap. C2. 1978. 90 p. 7-C3. A model for simulation of flow in singular and interconnected channels, by R.W. Schaffranek, R.A.Baltzer, and D.E.Goldberg: USGS–TWRI book 7, chap. C3. 1981. 110 p. 52 Book 8. Instrumentation Section A. Instruments for Measurement of Water Level 8-A1. Methods of measuring water levels in deep wells, by M.S. Garber and F.C. Koopman: USGS–TWRI book 8, chap. A1. 1968. 23 p. 8-A2. Installation and service manual for U.S. Geological Survey manometers, by J.D. Craig: USGS–TWRI book 8, chap. A2. 1983. 57 p. Section B. Instruments for Measurement of Discharge 8-B2. Calibration and maintenance of vertical-axis type current meters, by G.F. Smoot and C.E. Novak: USGS–TWRI book 8, chap. B2. 1968. 15 p. Book 9. Handbooks for Water-Resources Investigations Section A. National Field Manual for the Collection of Water-Quality Data 9-A1. National Field Manual for the Collection of Water-Quality Data: Preparations for Water Sampling, by F.D. Wilde, D.B. Radtke, Jacob Gibs, and R.T. Iwatsubo: USGS–TWRI book 9, chap. A1. 1998. 47 p. 9-A2. National Field Manual for the Collection of Water-Quality Data: Selection of Equipment for Water Sampling, edited by F.D. Wilde, D.B. Radtke, Jacob Gibs, and R.T. Iwatsubo: USGS–TWRI book 9, chap. A2. 1998. 94 p. 9-A3. National Field Manual for the Collection of Water-Quality Data: Cleaning of Equipment for Water Sampling, edited by F.D. Wilde, D.B. Radtke, Jacob Gibs, and R.T. Iwatsubo: USGS–TWRI book 9, chap. A3. 1998. 75 p. 9-A4. National Field Manual for the Collection of Water-Quality Data: Collection of Water Samples, edited by F.D. Wilde, D.B. Radtke, Jacob Gibs, and R.T. Iwatsubo: USGS–TWRI book 9, chap. A4. 1999. 156 p. 9-A5. National Field Manual for the Collection of Water-Quality Data: Processing of Water Samples, edited by F.D. Wilde, D.B. Radtke, Jacob Gibs, and R.T. Iwatsubo: USGS–TWRI book 9, chap. A5. 1999, 149 p. 9-A6. National Field Manual for the Collection of Water-Quality Data: Field Measurements, edited by F.D. Wilde and D.B. Radtke: USGS–TWRI book 9, chap. A6. 1998. Variously paginated. 9-A7. National Field Manual for the Collection of Water-Quality Data: Biological Indicators, edited by D.N. Myers and F.D. Wilde: USGS–TWRI book 9, chap. A7. 1997 and 1999. Variously paginated. 9-A8. National Field Manual for the Collection of Water-Quality Data: Bottom-material samples, by D.B. Radtke: USGS– TWRI book 9, chap. A8. 1998. 48 p. 9-A9. National Field Manual for the Collection of Water-Quality Data: Safety in Field Activities, by S.L. Lane and R.G. Fay: USGS–TWRI book 9, chap. A9. 1998. 60 p. 53 54 THIS PAGE IS INTENTIONALLY BLANK 55 Figure 10. Río Guajataca basin. 56 RIO GUAJATACA BASIN 50010500 RIO GUAJATACA AT LARES, PR WATER-QUALITY RECORDS LOCATION.--Lat 18q18'01", long 66q52'24", at bridge on Highway 111 (km 32.9), 0.1 mi (0.2 km) upstream from Quebrada Anón and 0.4 mi (0.6 km) northeast of Lares Plaza. DRAINAGE AREA.--3.16 mi2 (8.18 km2). PERIOD OF RECORD.--Water years 1958-71, 1974 to current year. WATER-QUALITY DATA, WATER YEAR OCTOBER 2002 TO SEPTEMBER 2003 Turbid ity, Dis- pH, Specif. Hard- Instan- wat unf solved water, conduc- ness, Magnes- Potas- taneous lab, Dis- oxygen, unfltrd tance, Temper- water, Calcium ium, sium, Sodium dis- Hach solved percent field, wat unf ature, unfltrd water, water, water, adsorp charge, 2100AN oxygen, of sat- std uS/cm water, mg/L as fltrd, fltrd, fltrd, tion Date Time cfs NTU mg/L uration units 25 degC deg C CaCO3 mg/L mg/L mg/L ratio (00061) (99872) (00300) (00301) (00400) (00095) (00010) (00900) (00915) (00925) (00935) (00931) DEC 11... 1300 1.6 2.3 8.1 94 6.3 256 21.9 92 27.2 5.92 2.25 .5 MAR 19... 1330 .45 2.4 8.7 -- 7.9 256 23.8 97 27.8 6.58 3.93 .6 MAY 12... 1630 11 7.5 8.1 -- 7.7 224 24.5 84 25.9 4.76 2.75 .4 AUG 20... 1615 4.5 12 7.2 -- 7.5 254 26.3 -- -- -- -- - SEP 16... 1100 3.4 2.1 8.0 -- 7.6 258 24.0 100 32.4 5.67 2.63 .4 ANC, Residue Residue Ammonia wat unf water, total + fixed Chlor- Fluor- fltrd, at 105 org-N, Ammonia Nitrate Sodium, end pt, ide, ide, Silica, Sulfate Sulfide sum of Residue deg. C, water, water, water water, field, water, water, water, water, water consti- water, sus- unfltrd unfltrd unfltrd fltrd, mg/L as fltrd, fltrd, fltrd, fltrd, unfltrd tuents fltrd, pended, mg/L mg/L mg/L Date mg/L CaCO3 mg/L mg/L mg/L mg/L mg/L mg/L tons/d mg/L as N as N as N (00930) (00410) (00940) (00950) (00955) (00945) (00745) (70301) (70302) (00530) (00625) (00610) (00620) DEC 11... 11.9 119 10.7 <.17 33.7 5.3 -- 168 .74 <10 .20 .03 1.74 MAR 19... 13.0 95 12.9 .09 30.5 11.1 .2 163 .20 <10 <.20 .01 - MAY 12... 9.35 59 9.51 <.17 24.4 9.2 .1 121 3.64 <10 <.20 <.01 - AUG 20... -- 92 -- -- -- -- -- -- -- <10 .30 .11 1.49 SEP 16... 10.2 101 11.0 <.2 26.6 8.8 -- 158 -- <10 <.20 <.01 - Nitrite Total Fecal Fecal Total + Organic Total nitro- COD, coli- strep- coli- Barium, Boron, nitrate Nitrite nitro- Phos- nitro- gen, high form, tococci form, water, water, water water, gen, phorus, gen, water, level, M-FC KF M-Endo, Arsenic unfltrd unfltrd unfltrd unfltrd water, water, water, unfltrd water, 0.7u MF MF, immed, water recover recover mg/L mg/L unfltrd unfltrd unfltrd mg/L unfltrd col/ col/ col/ unfltrd -able, -able, Date as N as N mg/L mg/L mg/L as NO3 mg/L 100 mL 100 mL 100 mL ug/L ug/L ug/L (00630) (00615) (00605) (00665) (00600) (71887) (00340) (31625) (31673) (31501) (01002) (01007) (01022) DEC 11... 1.80 .06 .17 .06 2.0 8.9 <10 2,000 880 -- -- -- - MAR 19... .800 <.01 -- .04 -- -- <10 200 -- 5,300 E1 17.8 E17 MAY 12... 1.70 <.01 -- .03 -- -- <10 640 -- 6,300 E2 23.2 29 AUG 20... 1.50 .01 .19 .03 1.8 8.0 10 E14,000 -- 57,000 -- -- - SEP 16... 1.40 <.01 -- .04 -- -- <10 300 -- 30,000 -- -- - 57 RIO GUAJATACA BASIN 50010500 RIO GUAJATACA AT LARES, PR—Continued WATER-QUALITY DATA, WATER YEAR OCTOBER 2002 TO SEPTEMBER 2003—CONTINUED Chrom- Mangan- Phen- ium, Copper, Iron, Lead, ese, Mercury Silver, Zinc, olic water, water, water, water, water, water, Selen- water, water, com- Cadmium unfltrd unfltrd Cyanide unfltrd unfltrd unfltrd unfltrd ium, unfltrd unfltrd MBAS, pounds, water, recover recover water recover recover recover recover water, recover recover water, water, unfltrd -able, -able, unfltrd -able, -able, -able, -able, unfltrd -able, -able, unfltrd unfltrd Date ug/L ug/L ug/L mg/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L mg/L ug/L (01027) (01034) (01042) (00720) (01045) (01051) (01055) (71900) (01147) (01077) (01092) (38260) (32730) DEC 11... -- -- -- -- -- -- -- -- -- -- -- -- -- MAR 19... <.2 <.8 <10 <.01 40 <1 11.9 <.02 <3 <.3 <25 <.10 <16 MAY 12... <.2 <.8 <10 <.01 220 <1 21.6 <.02 <3 <.3 <25 <.10 <16 AUG 20... -- -- -- -- -- -- -- -- -- -- -- -- -- SEP 16... -- -- -- -- -- -- -- -- -- -- -- -- -- < -- Less than E -- Estimated value --- --- --- --- --- --- --- 58 RIO GUAJATACA BASIN 50010800 LAGO GUAJATACA AT DAMSITE NEAR QUEBRADILLAS, PR LOCATION.--Lat 18q24'02", long 66q55'25", Hydrologic Unit 21010002, on right bank, in a concrete intake tower at Damsite, 5.2 mi (8.4 km) southeast from Quebradillas Plaza, 0.5 mi (0.8 km) northeast from Iglesia San Antonio de Padua and 2.8 mi (4.5 km) from Escuela Segunda Unidad Baldorioty de Castro. DRAINAGE AREA.--24.6 mi2 (63.71 km2). ELEVATION RECORDS PERIOD OF RECORD.--April 1995 to current year. GAGE.--Water-stage recorder. Datum of gage is mean sea level. REMARKS.--Lago Guajataca was completed in 1928. The dam is a semihydraulic earthfill structure about 123 ft (37 m) high, a top w idth of 31 ft (9.5 m) at crest elevation of 664 ft (202.5 m), a base width of 623 ft (190 m), a crest length of 1,036 ft (316 m) and has a maximum storage capacity of 49,200 acre- feet (60.6 hm3). The Guajataca Dam is owned by the Puerto Rico Electric Power Authority (PREPA) and provides water for the municipalities of Aguadilla, Isabela, Moca, Aguada, and Quebradillas although its primary purpose is for agricultural irrigation for the flatlands of the area. Gage-height and precipitation satellite telemetry at station. New capacity table based on U.S. Geological Survey Water-Resources Investigations Report 00-4044, January 1999. EXTREMES OBSERVED FOR PERIOD OF RECORD.--Maximum elevation 648.3 ft (197.60 m), September 23, 1998; minimum elevation, 608.07 ft (185.34 m) May 17, 1998. EXTREMES OBSERVED FOR CURRENT YEAR.--Maximum elevation, 643.58 ft (196.16 m), November 16; minimum elevation, 629.19 ft (191.78 m), April 5. Capacity Table (based on data from U.S. Geological Survey Water-Resources Investigations Report 00-4044, 1999) (Elevation in ft, capacity in acre-ft) Elevation Contents 557 0 577 916 597 5,253 Elevation Contents 616 13,393 636 26,332 646 34,277 ELEVATION ABOVE NGVD 1929, FEET WATER YEAR OCTOBER 2002 TO SEPTEMBER 2003 DAILY OBSERVATION AT 2400 HOURS DAY OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP 1 639.22 642.87 643.03 639.88 636.54 633.95 629.48 637.36 640.93 638.44 634.63 635.97 2 639.16 642.53 642.69 639.77 636.44 633.81 629.40 637.28 640.95 638.32 634.48 635.90 3 640.27 642.04 642.63 639.63 636.36 633.66 629.33 637.20 640.90 638.32 634.36 635.87 4 640.94 641.90 642.62 639.51 636.59 633.52 629.24 637.25 640.82 638.19 634.33 635.80 5 641.19 641.85 642.59 639.39 636.93 633.36 629.73 637.37 641.06 638.06 634.20 635.77 6 641.22 641.78 642.52 639.26 636.95 633.21 629.95 637.35 641.05 637.92 634.05 635.68 7 641.29 641.71 642.43 639.13 636.86 633.05 629.88 637.28 640.99 637.79 633.95 635.63 8 641.70 641.63 642.35 639.05 636.75 632.92 629.77 637.21 640.92 637.68 633.80 635.55 9 642.08 641.56 642.27 638.93 636.62 632.76 629.82 637.19 640.83 637.54 633.67 635.74 10 641.94 641.71 642.17 638.80 636.50 632.61 629.73 637.15 640.73 637.41 633.51 635.66 11 641.96 641.70 642.07 638.66 636.38 632.45 629.62 637.36 640.64 637.28 633.49 636.12 12 642.06 641.76 641.97 638.53 636.25 632.29 629.48 637.40 640.54 637.15 633.54 636.58 13 641.80 642.13 641.87 638.40 636.12 632.13 629.36 637.90 640.42 637.02 633.42 637.21 14 641.66 642.91 641.76 638.27 636.01 631.97 629.56 638.14 640.30 636.88 633.36 637.53 15 642.08 643.56 641.66 638.13 635.88 631.82 629.82 638.34 640.19 636.76 633.30 637.51 16 641.76 643.49 641.55 637.99 635.75 631.65 629.80 638.43 640.08 636.62 633.20 637.45 17 641.48 642.96 641.44 637.86 635.61 631.49 629.77 639.43 639.97 636.55 633.07 637.44 18 641.56 642.32 641.33 637.73 635.48 631.25 630.87 640.13 639.99 636.45 632.94 637.40 19 641.54 641.94 641.23 637.59 635.34 631.09 631.22 640.60 639.97 636.33 633.64 637.32 20 641.53 641.92 641.13 637.45 635.21 630.92 631.28 641.32 639.87 636.17 633.85 637.24 21 641.73 641.92 641.02 637.32 635.08 630.74 632.55 641.70 639.77 636.04 633.78 637.25 22 641.87 641.88 640.91 637.21 634.95 630.56 633.08 641.74 639.66 635.91 633.67 637.16 23 641.96 641.81 640.93 637.09 634.82 630.37 633.18 641.69 639.53 635.76 634.27 637.09 24 641.95 641.74 640.82 637.01 634.68 630.21 634.84 641.58 639.41 635.62 634.71 637.06 25 641.90 641.67 640.71 637.02 634.54 630.04 635.91 641.44 639.29 635.47 635.22 637.16 26 641.89 642.30 640.60 637.11 634.40 629.90 636.95 641.28 639.16 635.32 635.49 637.23 27 641.83 642.53 640.48 637.05 634.25 629.93 637.38 641.15 639.02 635.22 635.63 637.15 28 641.75 642.59 640.36 636.94 634.10 629.93 637.44 641.07 638.87 635.11 635.68 637.06 29 641.67 642.54 640.24 636.81 629.86 637.42 641.00 638.71 634.96 635.64 636.94 30 641.60 643.02 640.12 636.71 629.74 637.41 640.92 638.58 634.81 635.71 636.83 31 642.37 640.00 636.61 629.59 640.84 634.66 635.96 MAX 642.37 643.56 643.03 639.88 636.95 633.95 637.44 641.74 641.06 638.44 635.96 637.53 MIN 639.16 641.56 640.00 636.61 634.10 629.59 629.24 637.15 638.58 634.66 632.94 635.55 59 RIO GUAJATACA BASIN 50010800 LAGO GUAJATACA AT DAMSITE NEAR QUEBRADILLAS, PR—Continued O N D J F M A M J J A S 628 630 632 634 636 638 640 642 644 ELEVATION, IN FEET 2002 2003 60 RIO GUAJATACA BASIN 50011000 CANAL PRINCIPAL DE DIVERSIONES AT LAGO DE GUAJATACA, PR WATER-QUALITY RECORDS LOCATION.--Lat 18q24'02", long 66q55'27", off Highway 476 at Lago Guajataca outlet, 3.0 mi (4.8 km) southwest of Segunda Unidad Baldorioty de Castro, and 5.3 mi (8.5 km) south of Quebradillas Plaza. DRAINAGE AREA.--Indeterminate. PERIOD OF RECORD.--Water years 1958-64, 1974 to current year. WATER-QUALITY DATA, WATER YEAR OCTOBER 2002 TO SEPTEMBER 2003 Turbid ity, Dis- pH, Specif. Hard- Instan- wat unf solved water, conduc- ness, Magnes- Potas- taneous lab, Dis- oxygen, unfltrd tance, Temper- water, Calcium ium, sium, Sodium dis- Hach solved percent field, wat unf ature, unfltrd water, water, water, adsorp charge, 2100AN oxygen, of sat- std uS/cm water, mg/L as fltrd, fltrd, fltrd, tion Date Time cfs NTU mg/L uration units 25 degC deg C CaCO3 mg/L mg/L mg/L ratio (00061) (99872) (00300) (00301) (00400) (00095) (00010) (00900) (00915) (00925) (00935) (00931) DEC 05... 1440 70 2.9 .8 10 6.5 305 25.4 150 53.0 3.28 1.96 .2 MAR 27... 0900 70 4.2 6.9 -- 8.0 296 26.7 130 46.3 3.49 1.90 .2 MAY 14... 0855 60 6.3 .2 -- 7.2 340 25.3 160 58.1 3.61 2.09 .2 AUG 26... 1235 70 7.8 1.4 -- 7.2 313 27.1 -- -- -- -- - SEP 18... 0855 70 4.1 1.4 -- 7.3 314 27.0 140 52.0 3.60 2.09 .2 ANC, Residue Residue Ammonia wat unf water, total + fixed Chlor- Fluor- fltrd, at 105 org-N, Ammonia Nitrate Sodium, end pt, ide, ide, Silica, Sulfate Sulfide sum of Residue deg. C, water, water, water water, field, water, water, water, water, water consti- water, sus- unfltrd unfltrd unfltrd fltrd, mg/L as fltrd, fltrd, fltrd, fltrd, unfltrd tuents fltrd, pended, mg/L mg/L mg/L Date mg/L CaCO3 mg/L mg/L mg/L mg/L mg/L mg/L tons/d mg/L as N as N as N (00930) (00410) (00940) (00950) (00955) (00945) (00745) (70301) (70302) (00530) (00625) (00610) (00620) DEC 05... 4.74 138 5.66 <.17 7.3 6.7 -- 165 48.2 <10 .50 .12 - MAR 27... 5.51 130 6.56 .12 6.7 7.5 <.1 156 45.5 <10 .30 .04 - MAY 14... 5.48 148 8.05 <.17 7.2 9.0 <.1 182 45.7 <10 .40 .12 - AUG 26... -- 137 -- -- -- -- -- -- -- <10 .60 .34 - SEP 18... 5.10 140 7.91 <.2 7.3 9.1 -- 171 49.9 <10 .50 .12 .05 Nitrite Total Fecal Fecal Total + Organic Total nitro- COD, coli- strep- coli- Barium, Boron, nitrate Nitrite nitro- Phos- nitro- gen, high form, tococci form, water, water, water water, gen, phorus, gen, water, level, M-FC KF M-Endo, Arsenic unfltrd unfltrd unfltrd unfltrd water, water, water, unfltrd water, 0.7u MF MF, immed, water recover recover mg/L mg/L unfltrd unfltrd unfltrd mg/L unfltrd col/ col/ col/ unfltrd -able, -able, Date as N as N mg/L mg/L mg/L as NO3 mg/L 100 mL 100 mL 100 mL ug/L ug/L ug/L (00630) (00615) (00605) (00665) (00600) (71887) (00340) (31625) (31673) (31501) (01002) (01007) (01022) DEC 05... <.020 <.01 .38 <.02 -- -- <10 E8 E4 -- -- -- - MAR 27... <.020 <.01 .26 <.02 -- -- <10 <1 -- E49 <2 3.3 <18 MAY 14... .280 <.01 .28 <.02 .68 3.0 10 E12 -- 45 E2 13.1 E12 AUG 26... <.020 <.01 .26 <.02 -- -- 10 100 -- E560 -- -- - SEP 18... .060 .01 .38 <.02 .56 2.5 10 E6 -- 44 -- -- - 61 RIO GUAJATACA BASIN 50011000 CANAL PRINCIPAL DE DIVERSIONES AT LAGO DE GUAJATACA, PR—Continued WATER-QUALITY DATA, WATER YEAR OCTOBER 2002 TO SEPTEMBER 2003—CONTINUED Chrom- Mangan- Phen- ium, Copper, Iron, Lead, ese, Mercury Silver, Zinc, olic water, water, water, water, water, water, Selen- water, water, com- Cadmium unfltrd unfltrd Cyanide unfltrd unfltrd unfltrd unfltrd ium, unfltrd unfltrd MBAS, pounds, water, recover recover water recover recover recover recover water, recover recover water, water, unfltrd -able, -able, unfltrd -able, -able, -able, -able, unfltrd -able, -able, unfltrd unfltrd Date ug/L ug/L ug/L mg/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L mg/L ug/L (01027) (01034) (01042) (00720) (01045) (01051) (01055) (71900) (01147) (01077) (01092) (38260) (32730) DEC 05... -- -- -- -- -- -- -- -- -- -- -- -- -- MAR 27... <.2 <.8 <10 <.01 50 <1 22.9 <.02 <3 <.3 <25 <.10 <16 MAY 14... <.2 <.8 M <.01 40 <1 68.3 <.02 E1 <.3 E17 <.10 <16 AUG 26... -- -- -- -- -- -- -- -- -- -- -- -- -- SEP 18... -- -- -- -- -- -- -- -- -- -- -- -- -- < -- Less than E -- Estimated value M -- Presence verified, not quantified 62 RIO GUAJATACA BASIN 50011400 RIO GUAJATACA ABOVE MOUTH NEAR QUEBRADILLAS, PR WATER-QUALITY RECORDS LOCATION.--Lat 18q28'31", long 66q57'46", Hydrologic Unit 21010002, on left bank at ford 1.7 mi (2.7 km) upstream from bridge on Highway 2, 1.6 mi (2.6 km) west of Quebradillas Plaza, 2.1 mi (3.4 km) upstream from Atlantic Ocean, and 6.6 mi (10.6 km) downstream from Lago Guajatac a. DRAINAGE AREA.--Indeterminate PERIOD OF RECORD.--Water years 1969 to current year. WATER-QUALITY DATA, WATER YEAR OCTOBER 2002 TO SEPTEMBER 2003 Turbid ity, Dis- pH, Specif. Hard- Instan- wat unf solved water, conduc- ness, Magnes- Potas- taneous lab, Dis- oxygen, unfltrd tance, Temper- water, Calcium ium, sium, Sodium dis- Hach solved percent field, wat unf ature, unfltrd water, water, water, adsorp charge, 2100AN oxygen, of sat- std uS/cm water, mg/L as fltrd, fltrd, fltrd, tion Date Time cfs NTU mg/L uration units 25 degC deg C CaCO3 mg/L mg/L mg/L ratio (00061) (99872) (00300) (00301) (00400) (00095) (00010) (00900) (00915) (00925) (00935) (00931) DEC 06... 0915 17 2.5 6.8 79 6.8 483 23.6 220 75.5 7.24 1.33 .4 MAR 26... 1430 7.3 4.4 8.4 -- 7.5 630 25.6 260 86.4 11.1 1.07 .7 MAY 15... 0845 12 1.8 8.9 -- 8.1 234 26.2 220 75.7 8.27 1.41 .6 AUG 26... 1050 26 5.5 6.3 -- 7.5 375 25.2 -- -- -- -- - SEP 18... 1050 12 2.3 5.9 -- 7.3 522 25.1 220 73.6 7.88 1.47 .5 ANC, Residue Residue Ammonia wat unf water, total + fixed Chlor- Fluor- fltrd, at 105 org-N, Ammonia Nitrate Sodium, end pt, ide, ide, Silica, Sulfate Sulfide sum of Residue deg. C, water, water, water water, field, water, water, water, water, water consti- water, sus- unfltrd unfltrd unfltrd fltrd, mg/L as fltrd, fltrd, fltrd, fltrd, unfltrd tuents fltrd, pended, mg/L mg/L mg/L Date mg/L CaCO3 mg/L mg/L mg/L mg/L mg/L mg/L tons/d mg/L as N as N as N (00930) (00410) (00940) (00950) (00955) (00945) (00745) (70301) (70302) (00530) (00625) (00610) (00620) DEC 06... 15.1 197 25.6 <.17 6.8 7.3 -- 257 11.7 <10 <.20 <.01 - MAR 26... 27.0 231 48.9 <.17 6.7 7.6 <.1 327 6.49 <10 <.20 .02 3.29 MAY 15... 20.6 89 37.1 <.17 6.1 8.2 <.1 211 6.71 <10 <.20 .02 - AUG 26... -- 154 -- -- -- -- -- -- -- <10 <.20 .02 - SEP 18... 18.0 201 36.5 <.2 6.7 8.2 -- 273 8.90 <10 <.20 .08 - Nitrite Fecal Fecal Total Chrom + COD, coli- strep- coli- Barium, Boron, ium, Copper, nitrate Nitrite Phos- high form, tococci form, water, water, water, water, water water, phorus, level, M-FC KF M-Endo, Arsenic unfltrd unfltrd Cadmium unfltrd unfltrd unfltrd unfltrd water, water, 0.7u MF MF, immed, water recover recover water, recover recover mg/L mg/L unfltrd unfltrd col/ col/ col/ unfltrd -able, -able, unfltrd -able, -able, Date as N as N mg/L mg/L 100 mL 100 mL 100 mL ug/L ug/L ug/L ug/L ug/L ug/L (00630) (00615) (00665) (00340) (31625) (31673) (31501) (01002) (01007) (01022) (01027) (01034) (01042) DEC 06... 2.00 <.01 <.02 <10 76 E167 -- -- -- -- -- -- - MAR 26... 3.30 .01 <.02 <10 E130 -- 4,700 <2 8.1 36 <.2 1.3 <10 MAY 15... 2.10 <.01 <.02 <10 E13 -- 450 <2 10.0 21 <.2 E.7 M AUG 26... .820 <.01 <.02 <10 54 -- E10,600 -- -- -- -- -- - SEP 18... 2.10 <.01 <.02 <10 50 -- E1,800 -- -- -- -- -- - 63 RIO GUAJATACA BASIN 50011400 RIO GUAJATACA ABOVE MOUTH NEAR QUEBRADILLAS, PR—Continued WATER-QUALITY DATA, WATER YEAR OCTOBER 2002 TO SEPTEMBER 2003—CONTINUED Mangan- Phen- Iron, Lead, ese, Mercury Silver, Zinc, olic water, water, water, water, Selen- water, water, com- Cyanide unfltrd unfltrd unfltrd unfltrd ium, unfltrd unfltrd MBAS, pounds, water recover recover recover recover water, recover recover water, water, unfltrd -able, -able, -able, -able, unfltrd -able, -able, unfltrd unfltrd Date mg/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L mg/L ug/L (00720) (01045) (01051) (01055) (71900) (01147) (01077) (01092) (38260) (32730) DEC 06... -- -- -- -- -- -- -- -- -- -- MAR 26... <.01 60 <1 15.5 <.02 <3 <.3 <25 <.10 <16 MAY 15... <.01 40 <1 9.0 <.02 <3 <.3 <25 <.10 <16 AUG 26... -- -- -- -- -- -- -- -- -- -- SEP 18... -- -- -- -- -- -- -- -- -- -- < -- Less than E -- Estimated value M -- Presence verified, not quantified 64 THIS PAGE IS INTENTIONALLY BLANK Río Camuy basin. 65 Figure 11. Figure 11. Río Camuy basin. 66 RIO CAMUY BASIN 50014800 RIO CAMUY NEAR BAYANEY, PR LOCATION.--Lat 18q23'48", long 66q49'04", Hydrologic Unit 21010002, on left bank at Highway 488, 1.4 mi (2.2 km) southeast of school at Santiago, 0.9 mi (1.4 km) northwest from Escuela Manuel A. Rivera at Bayaney and 9.1 mi (14.6 km) upstream from mouth. DRAINAGE AREA.--Indeterminate. PERIOD OF RECORD.--May 1984 to current year. GAGE.--Water-stage recorder. Elevation of gage is 341 ft (104 m), from topographic map. REMARKS.--Records fair except those for estimated daily discharges, which are poor. Gage-height and precipitation satellite telemetry at station. DISCHARGE, CUBIC FEET PER SECOND WATER YEAR OCTOBER 2002 TO SEPTEMBER 2003 DAILY MEAN VALUES DAY OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP 1 87 297 84 49 2 112 221 72 49 3 113 141 69 49 4 208 93 68 48 5 206 82 74 47 e43 32 e38 75 81 41 e41 e112 e43 32 75 67 85 e43 e38 e74 e41 31 47 60 80 e47 37 e68 e61 31 45 60 73 e42 e69 e71 e71 30 88 130 70 41 e77 e60 6 108 76 69 46 7 155 76 64 46 8 189 69 63 e45 9 169 67 63 e45 10 147 84 61 45 e62 30 123 138 70 42 49 e52 45 30 63 78 67 40 46 e49 41 30 42 85 62 40 43 e65 39 31 38 98 60 40 35 60 38 30 35 188 59 38 33 50 11 116 74 59 e44 12 92 79 58 43 13 108 483 57 43 14 138 493 58 42 15 181 309 56 42 37 30 34 168 58 37 e32 e79 37 30 35 172 57 e35 e43 e80 37 30 56 124 55 e35 e34 e100 38 29 78 123 54 e34 e34 e173 37 29 136 136 52 e34 67 73 16 159 227 55 41 17 108 171 55 42 18 89 121 57 40 19 82 105 e53 39 20 76 96 53 38 36 29 62 147 52 34 e55 63 35 28 45 219 51 32 44 54 35 28 175 241 53 32 36 52 34 32 174 201 71 38 66 e49 35 37 95 388 55 33 119 e52 21 224 94 51 38 22 144 87 52 e38 23 119 82 137 42 24 118 79 101 e39 25 88 77 69 e71 36 33 306 280 51 33 e69 e63 34 30 266 193 49 e33 e46 88 33 29 145 159 47 32 e46 85 33 29 359 131 45 32 e147 96 33 29 419 112 45 e31 e163 117 26 91 87 58 e108 27 85 90 55 e71 28 74 75 52 e54 29 69 73 51 e45 30 67 72 e50 e43 31 94 --- e49 e42 33 29 262 100 45 e41 e137 236 34 35 162 95 45 36 e78 174 32 40 106 87 43 45 e72 125 --- e41 88 82 45 42 e64 80 --- e47 80 77 42 35 e57 69 --- e33 --- 74 --- 35 e171 -- TOTAL 3,816 4,180 1,973 1,474 MEAN 123 139 63.6 47.5 MAX 224 493 137 108 MIN 67 67 49 38 1,113 984 3,677 4,288 1,722 1,153 2,048 2,569 39.8 31.7 123 138 57.4 37.2 66.1 85.6 71 47 419 388 85 47 171 236 32 28 34 60 42 31 32 49 STATISTICS OF MONTHLY MEAN DATA FOR WATER YEARS 1984 - 2003, BY WATER YEAR (WY) MEAN 197 138 76.1 58.4 MAX 427 310 179 163 (WY) (1986) (2002) (2000) (1997) MIN 81.6 53.4 30.2 33.1 (WY) (1988) (1998) (2001) (1991) 49.8 47.0 94.7 165 112 72.6 95.6 183 96.4 93.7 289 624 322 109 187 726 (1996) (1999) (2002) (1986) (1999) (1989) (1998) (1998) 29.1 23.7 28.0 43.2 42.7 37.2 47.9 61.8 (1998) (1994) (1994) (1989) (1997) (2003) (1993) (1997) SUMMARY STATISTICS FOR 2002 CALENDAR YEAR FOR 2003 WATER YEAR WATER YEARS 1984 - 2003 ANNUAL TOTAL 40,431 ANNUAL MEAN 111 HIGHEST ANNUAL MEAN LOWEST ANNUAL MEAN HIGHEST DAILY MEAN 791 LOWEST DAILY MEAN 26 ANNUAL SEVEN-DAY MINIMUM 27 MAXIMUM PEAK FLOW MAXIMUM PEAK STAGE INSTANTANEOUS LOW FLOW 10 PERCENT EXCEEDS 221 50 PERCENT EXCEEDS 74 90 PERCENT EXCEEDS 40 28,997 79.4 107 179 1986 61.5 1994 Apr 8 493 Nov 14 9,010 Sep 22, 1998 Mar 23 28 Mar 17 16 Mar 18, 1994 Mar 20 29 Mar 12 17 Mar 16, 1994 5,440 Nov 13 11,600 Sep 22, 1998 16.76 Nov 13 21.69 Sep 22, 1998 27 Mar 16 15 Mar 22, 1994 159 209 58 67 33 33 e Estimated 67 RIO CAMUY BASIN 50014800 RIO CAMUY NEAR BAYANEY, PR—Continued O N D J F M A M J J A S 10 20 50 100 100 200 500 1,000 DISCHARGE, IN CUBIC FEET PER SECOND 2002 2003 68 THIS PAGE IS INTENTIONALLY BLANK 69 Figure 12. Río Grande de Arecibo basin. 70 RIO GRANDE DE ARECIBO BASIN 50020100 LAGO GARZAS NEAR ADJUNTAS, PR LOCATION.--Lat 18q08'20", long 66q44'29", Hydrologic Unit 21010002, in power gate tower of Garzas Dam on Río Vacas, 1.7 mi (2.7 km) upstream from Río Garzas, and 2.2 mi (3.5 km) southwest of Adjuntas. DRAINAGE AREA.--15.6 mi2 (40.4 km2). PERIOD OF RECORD.--January 1988 to May 1989, March 1993 to current year. GAGE.--Water-stage recorder. Datum of gage is 2,400.00 ft (731.52 m) above mean sea level. Prior to May 25, 1988, at datum 2,376 .80 ft (724.45 m), May 25 to July 13, 1988, at datum 2,338.08 ft (712.65 m), July 14, 1988, to May 25, 1989, at datum 2,337.82 ft (712.56 m), above mean sea level. REMARKS.--Lake is formed by earthfill dam completed in 1943. Outflow from lake controlled by vertical-lift sluice gate and fixed -crest concrete spillway. Spillway elevation, 2,415.00 ft (736.09 m).Lake is used for irrigation and power production. Operated by Puerto Rico Electric Po wer Authorithy. Gage- height and precipitation satellite telemetry at station. New capacity table based on U.S. Geological Survey Water-Resources Investigations Report 99-4143, September 1996. EXTREMES OBSERVED FOR PERIOD OF RECORD.--Maximum elevation 2,418.28 ft (737.09 m), September 22, 1998; minimum elevation, 2,364.79 ft (720.79 m), August 23, 1988. EXTREMES OBSERVED FOR CURRENT YEAR.--Maximum elevation, 2,416.68 ft (736.60 m), October 10; minimum elevation, 2,412.17 ft (735.23 m), June 26. Capacity Table (based on data from U.S. Geological Survey Water-Resources Investigations Report 99-4143, 1996) (Elevation in ft, capacity in acre-ft) Elevation Contents 2,317 0 2,336 243 2,359 794 Elevation Contents 2,376 1,419 2,399 2,700 2,415 4,143 ELEVATION ABOVE NGVD 1929, FEET WATER YEAR OCTOBER 2002 TO SEPTEMBER 2003 DAILY OBSERVATION AT 2400 HOURS DAY OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP 1 2,415.71 A 2,415.33 2,414.95 2,414.73 2,414.43 2,414.94 2,414.96 2,414.97 2,414.26 2,414.86 2,415.03 2 2,415.72 A 2,415.32 2,414.97 2,415.12 2,414.53 2,414.73 2,414.96 2,414.97 2,414.35 2,414.86 2,414.99 3 2,415.67 A 2,415.28 2,414.94 2,415.01 2,414.64 2,415.05 2,414.96 2,414.94 2,414.43 2,414.86 2,414.89 4 2,415.78 A 2,415.27 2,414.94 2,415.00 2,414.76 2,414.93 2,414.95 2,414.93 2,414.49 2,414.86 2,414.88 5 2,415.64 A 2,415.22 2,414.94 2,415.01 2,414.86 2,414.97 2,414.98 2,415.01 2,414.71 2,414.85 2,414.87 6 2,415.63 A 2,415.15 2,414.94 2,415.00 2,414.91 2,414.91 2,414.96 2,414.95 2,414.80 2,414.92 2,414.98 7 2,415.60 2,416.01 2,415.12 2,414.96 2,414.99 2,414.66 2,414.55 2,415.03 2,414.94 2,414.85 2,414.88 2,415.13 8 2,415.66 2,415.99 2,415.12 2,414.96 2,414.97 2,414.80 2,414.71 2,415.06 2,414.94 2,414.90 2,414.86 2,415.01 9 2,415.61 2,416.08 2,415.06 2,414.96 2,414.97 2,414.89 2,414.88 2,414.99 2,414.94 2,414.84 2,414.86 2,414.98 10 2,415.63 2,415.99 2,415.04 2,415.02 2,414.98 2,414.81 2,414.91 2,414.98 2,414.95 2,414.87 2,414.85 2,415.10 11 2,415.55 2,415.96 2,415.02 2,414.95 2,414.98 2,414.77 2,414.65 2,414.98 2,414.91 2,414.88 2,414.86 2,415.08 12 2,415.52 2,416.04 2,414.98 2,414.94 2,414.97 2,414.73 2,414.80 2,414.98 2,414.93 2,414.89 2,414.85 2,415.23 13 2,415.48 2,416.01 2,414.96 2,414.94 2,414.97 2,414.82 2,414.87 2,414.96 2,414.96 2,414.91 2,414.95 2,415.06 14 2,415.01 2,415.88 2,414.96 2,414.95 2,414.62 A 2,414.91 2,414.97 2,414.96 2,414.90 2,414.90 2,415.05 15 2,415.35 2,415.82 2,414.96 2,414.96 2,414.75 2,414.87 2,414.91 2,414.97 2,414.96 2,414.91 2,414.87 2,415.11 16 2,415.42 2,415.78 2,414.96 2,414.96 2,414.88 A 2,414.95 2,415.00 2,414.94 2,414.94 2,414.87 2,415.04 17 2,415.31 2,415.76 2,415.12 2,414.95 2,414.93 A 2,415.02 2,415.01 2,414.94 2,414.90 2,414.89 2,415.04 18 2,415.37 2,415.78 2,414.97 2,414.94 2,414.95 A 2,415.11 2,414.94 2,414.95 2,414.89 2,414.90 2,415.14 19 2,415.34 2,415.71 2,414.96 2,414.93 2,414.96 2,414.70 2,415.02 2,414.96 2,414.94 2,414.89 2,414.89 2,415.13 20 2,415.31 2,415.66 2,414.94 2,414.92 2,414.95 2,414.80 2,415.02 2,414.97 2,414.92 2,414.90 2,414.89 2,415.06 21 2,415.26 2,415.83 2,414.93 2,414.97 2,414.41 2,414.75 2,414.99 2,415.09 2,414.92 2,414.88 2,414.84 2,415.09 22 2,415.22 2,415.64 2,415.01 2,414.90 2,414.56 2,414.81 2,415.04 2,415.00 2,414.92 2,414.88 2,414.86 2,415.03 23 2,415.20 2,415.61 2,414.96 2,415.01 2,414.64 2,414.79 2,414.94 2,414.97 2,414.78 2,414.88 2,414.90 2,415.02 24 2,415.17 2,415.58 2,414.95 2,415.05 2,414.78 2,414.68 2,415.00 2,414.95 2,414.85 2,414.87 2,414.93 2,415.03 25 2,415.14 2,415.18 2,414.95 2,415.06 2,414.91 2,414.67 2,414.76 2,414.94 2,413.07 2,414.88 2,414.97 2,415.04 26 2,415.12 2,415.53 2,414.94 2,415.00 2,414.93 2,414.93 2,414.97 2,414.94 2,413.81 2,414.97 2,415.01 2,415.01 27 2,415.08 2,415.47 2,414.93 2,414.98 2,414.94 2,414.93 2,414.97 2,414.94 2,413.90 2,414.95 2,414.96 2,415.01 28 2,415.06 2,415.44 2,414.92 2,414.98 2,414.32 2,414.91 2,414.95 2,414.96 2,413.99 2,414.97 2,415.03 2,414.97 29 2,415.07 2,415.41 2,414.93 2,414.98 --- 2,414.91 2,414.94 2,414.97 2,414.06 2,414.90 2,415.04 2,415.05 30 A 2,415.36 2,414.94 2,414.98 --- 2,414.88 2,414.96 2,414.78 2,414.15 2,414.88 2,414.95 2,415.01 31 A --- 2,414.93 2,414.58 --- 2,414.90 --- 2,414.93 --- 2,414.87 2,414.95 -- MAX --- --- 2,415.33 2,415.06 2,415.12 --- 2,415.11 2,415.09 2,415.01 2,414.97 2,415.04 2,415.23 MIN --- --- 2,414.92 2,414.58 2,414.32 --- 2,414.55 2,414.78 2,413.07 2,414.26 2,414.84 2,414.87 A No gage-height record 71 RIO GRANDE DE ARECIBO BASIN 50020100 LAGO GARZAS NEAR ADJUNTAS, PR—Continued O N D J F M A M J J A S 2,413.0 2,413.5 2,414.0 2,414.5 2,415.0 2,415.5 2,416.0 2,416.5 ELEVATION, IN FEET GAP INDICATES MISSING RECORD 2002 2003 --- --- --- --- --- --- --- 72 RIO GRANDE DE ARECIBO BASIN 50020500 RIO GRANDE DE ARECIBO NEAR ADJUNTAS, PR LOCATION.--Lat 18q10'54", long 66q44'12", Hydrologic Unit 21010002, at Highway 135 bridge junction with Highway 10, 1.4 mi (2.2 km) south from Lago Adjuntas and 1.5 mi (2.4 km) northwest of Adjuntas Plaza. DRAINAGE AREA.--12.7 mi2 (32.9 km2), this does not include 6.0 mi2 (15.6 km2) above Lago Garzas. WATER-DISCHARGE RECORDS PERIOD OF RECORD.--November 1946 to April 1950 (operated by Puerto Rico Water Resources Authority), March 2000 to current year. GAGE.--Water-stage recorder. Elevation of gage is 1,443 ft (440 m), from topographic map. REMARKS.--Records poor. Flow affected by Lago Garzas, 2.63 mi (4.23 km) and sewage treatment plant 1.1 mi (1.77 km) upstream fro m gage. Gage-height and precipitation satellite telemetry at station. DISCHARGE, CUBIC FEET PER SECOND WATER YEAR OCTOBER 2002 TO SEPTEMBER 2003 DAILY MEAN VALUES DAY OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP 1 11 59 34 37 11 11 18 32 25 8.2 8.5 105 2 27 44 34 41 294 11 19 32 27 8.6 7.7 59 3 31 126 34 40 200 11 262 29 22 7.5 7.8 79 4 184 53 42 33 62 10 54 28 17 6.9 7.5 18 5 64 38 37 31 228 11 152 30 179 14 6.8 12 6 35 34 31 31 74 14 35 32 63 8.5 10 11 7 33 32 27 31 45 16 18 58 31 7.6 13 209 8 91 30 47 31 34 11 11 68 27 9.7 9.0 61 9 176 110 33 31 29 11 14 51 26 12 7.3 24 10 312 65 27 43 27 15 16 32 25 10 6.8 200 11 114 40 28 40 28 11 19 28 25 12 8.4 282 12 78 185 e29 28 27 9.9 14 27 21 12 7.1 525 13 55 283 e27 26 26 9.2 13 26 26 15 70 226 14 38 91 e26 25 22 11 15 35 25 15 30 70 15 16 50 e26 26 13 13 17 28 25 15 20 344 16 46 113 e424 26 13 14 35 114 24 75 14 134 17 38 50 e203 26 19 13 171 62 23 24 17 64 18 142 83 139 22 22 11 580 46 21 15 17 289 19 137 75 53 22 24 11 220 25 23 13 16 346 20 151 52 44 21 24 9.7 115 30 20 11 12 162 21 92 82 38 23 22 10 86 395 18 13 11 214 22 54 e42 420 20 13 9.3 108 164 18 11 10 102 23 51 e38 107 30 12 10 75 55 15 10 8.5 67 24 45 e34 61 35 12 10 84 33 9.4 9.4 9.8 57 25 40 e25 51 110 12 11 52 27 11 12 15 59 26 38 31 48 63 18 11 29 24 9.8 13 62 54 27 35 42 43 31 22 26 42 22 8.4 23 30 42 28 34 38 38 25 19 29 40 21 8.2 21 60 36 29 126 45 36 25 19 33 23 8.4 21 124 70 30 52 38 37 24 18 32 19 8.4 12 47 54 31 60 35 20 12 12 9.7 23 TOTAL 2,406 2,028 2,259 1,017 1,352 399.1 2,379 1,608 789.6 455.1 696.2 3,975 MEAN 77.6 67.6 72.9 32.8 48.3 12.9 79.3 51.9 26.3 14.7 22.5 132 MAX 312 283 424 110 294 29 580 395 179 75 124 525 MIN 11 25 26 20 11 9.2 11 12 8.2 6.9 6.8 11 AC-FT 4,770 4,020 4,480 2,020 2,680 792 4,720 3,190 1,570 903 1,380 7,880 CFSM 6.11 5.32 5.74 2.58 3.80 1.01 6.24 4.08 2.07 1.16 1.77 10.4 IN. 7.05 5.94 6.62 2.98 3.96 1.17 6.97 4.71 2.31 1.33 2.04 11.64 STATISTICS OF MONTHLY MEAN DATA FOR WATER YEARS 1947 - 2003, BY WATER YEAR (WY) MEAN 77.4 55.0 41.8 23.6 27.7 15.1 34.3 39.0 27.0 25.6 44.9 91.6 MAX 119 75.2 72.9 32.8 56.9 21.6 95.1 72.2 36.0 49.3 94.5 132 (WY) (2001) (2001) (2003) (2003) (1950) (1949) (2002) (2001) (2000) (1949) (2000) (2003) MIN 48.6 27.3 30.8 19.7 14.8 10.2 10.4 12.2 14.7 14.7 22.5 55.8 (WY) (2002) (1950) (1947) (1948) (2002) (2001) (1948) (1948) (2001) (2003) (2003) (1947) 73 RIO GRANDE DE ARECIBO BASIN 50020500 RIO GRANDE DE ARECIBO NEAR ADJUNTAS, PR—Continued DISCHARGE, SUMMARY STATISTICS FOR 2002 CALENDAR YEAR FOR 2003 WATER YEAR WATER YEARS 1947 - 2003 IN CUBIC FEET PER SECOND ANNUAL TOTAL 16,601.7 ANNUAL MEAN 45.5 HIGHEST ANNUAL MEAN LOWEST ANNUAL MEAN HIGHEST DAILY MEAN 424 LOWEST DAILY MEAN 8.6 ANNUAL SEVEN-DAY MINIMUM 8.9 MAXIMUM PEAK FLOW MAXIMUM PEAK STAGE ANNUAL RUNOFF (AC-FT) 32,930 ANNUAL RUNOFF (CFSM) 3.58 ANNUAL RUNOFF (INCHES) 48.63 10 PERCENT EXCEEDS 94 50 PERCENT EXCEEDS 27 90 PERCENT EXCEEDS 11 19,364.0 53.1 43.2 53.1 2003 39.5 2002 Dec 16 580 Apr 18 1,510 Aug 23, 2000 Jul 25 6.8 Aug 5 6.8 Mar 31, 2001 Mar 22 8.0 Jun 28 7.1 Mar 27, 2001 4,740 Sep 12 12,000 May 6, 2001 11.21 Sep 12 15.49 May 6, 2001 38,410 31,330 4.18 3.41 56.72 46.27 125 90 28 25 10 11 e Estimated 1,000 500 200 100