The surface-water assessment portion of this study focused on analysis of low-flow characteristics in local streams and rivers, because the supply of safe drinking water was a critical issue during recent dry periods. Low-flow characteristics were evaluated at one continuous-record gaging station based on graphical curve-fitting techniques and log-Pearson Type III frequency curves. Estimates of low-flow characteristics for 20 partial-record stations were generated using graphical-correlation techniques. Flow-duration characteristics for the continuous- and partial-record stations were estimated using the relation curves developed for the low-flow study. Stream low-flow statistics document the general hydrology under current land use, water-use, and climatic conditions.
A survey of streams and rivers utilized 37 sampling stations to evaluate the sanitary quality of about 165 miles of stream channels. River and stream samples for fecal coliform and fecal streptococcus analyses were collected on two occasions at base-flow conditions. Bacteriological analyses indicate that a significant portion of the stream reaches within the municipio of Mayagüez may have fecal coliform bacteria concentrations above the water-quality goal (standard) established by the Puerto Rico Environmental Quality Board (Junta de Calidad Ambiental de Puerto Rico) for inland surface waters. Sources of fecal contamination may include: illegal discharge of sewage to storm-water drains, malfunctioning sanitary sewer ejectors, clogged and leaking sewage pipes, septic tank leakage, unfenced livestock, and runoff from livestock pens. Long-term fecal coliform data from five sampling stations located within or in the vicinity of the municipio of Mayagüez have been in compliance with the water-quality goal for fecal coliform concentration established in July 1990.
Geologic, topographic, soil, hydrogeologic, and streamflow data were compiled into a database and used to divide the municipio of Mayagüez into five hydrogeologic terranes. This integrated database then was used to evaluate the ground-water potential of each hydrogeologic terrane. Lineament-trace analysis was used to help assess the ground-water development potential in the hydrogeologic terranes containing igneous rocks. Analyses suggest that areas with slopes greater than 15 degrees have relatively low ground-water development potential. The presence of fractures, independent of the topographic slope, may locally enhance the water-bearing properties in the hydrogeologic terranes containing igneous rocks. The results of this study indicate that induced streamflow generally is needed to sustain low to moderate ground-water withdrawal rates in the five hydrogeologic terranes. The ground-water flow systems in the hydrogeologic terranes are only able to sustain small withdrawal rates that rarely exceed 50 gallons per minute. Areas with a high density of fractures, as could be the case at the intersection of lineament traces in the upper parts of the Río Cañas and Río Yagüez watersheds, are worthy of exploratory drilling for ground-water development.
Abstract
Sumario
Introduction
Previous Studies
Chapter A: Surface-Water Resources Assessment of the Municipio of Mayagüez, Puerto Rico, 1999-2002
Purpose and Scope
Methodology
Results and Interpretation
Low Flow at a Continuous-Record Gaging Station
Low Flow at Partial-Record Stations
Flow-Duration Characteristics
Drainage-Basin Area/Discharge Relation
Map Features
Potential Reservoir Sites
Flood-Prone Areas
Saltwater Wedge at Streams
Public Water-Supply Filtration Plants and Waste-Water Treatment Facilities
Chapter B: Sanitary Quality of Surface Water During Base-Flow Conditions in the Municipio of Mayagüez, Puerto Rico, 2000-01
Purpose and Scope
Background
Methodology
Field-Data Collection
Analytical Techniques
Results and Interpretation
Upper Río Guanajibo Basin
Quebrada Sábalos Basin (Barrios Sábalos and Río Hondo)
Caño Corazones Basin (Barrios Sábalos and Río Hondo)
Río Yagüez Basin
Quebrada del Oro Basin (Barrio Miradero)
Caño Boquilla Basin (Barrios Sabanetas, Río Cañas, and Miradero)
Río Grande de Añasco Basin
Chapter C: Hydrogeologic Terranes and Ground-Water Resources in the Municipio of Mayagüez, Puerto Rico, 1999-2002
Purpose and Scope
Methodology
Hydrogeologic Terranes
Ground-Water Quality
Delineation of Coastal Saline Ground-Water Zone
Lineament-Trace Analysis
Base-Flow Measurements
Results and Interpretation
Hydrogeologic Terranes
Mayagüez Hydrogeologic Terrane 1 (MayHT1)
Upper Zone
Lower Zone
Mayagüez Hydrogeologic Terrane 2 (MayHT2)
Mayagüez Hydrogeologic Terrane 3 (MayHT3)
Mayagüez Hydrogeologic Terrane 4 (MayHT4)
Mayagüez Hydrogeologic Terrane 5 (MayHT5)
Ground-Water Quality
Ground-Water Withdrawals
Lineament-Trace Analysis
Summary and Conclusions
Acknowledgments
Cited References
The citation for this report, in USGS format, is as follows:
Rodríguez-Martínez, Jesús, Santiago-Rivera, Luis, Guzmán-Ríos, Senén, Gómez-Gómez, Fernando, and Oliveras-Feliciano, M.L., 2004, Surface-water, water-quality, and ground-water assessment of the municipio of Mayagüez, Puerto Rico, 1999-2002: U.S. Geological Survey Water-Resources Investigations Report 03-4317, 68 p., 2 pls.
Plate 1 (3.5MB) shows: Streamflow and bacteriological data collection sites, selected hydrologic features, and sanitary classification of streams with drainage to or within the municipio of Mayagüez, Puerto Rico
Plate 2 (3.3MB) shows: Hydrogeologic terranes, selected subbasins, geophysical transects, lineament traces, and well locations within the municipio of Mayagüez, Puerto Rico
Please visit http://pr.water.usgs.gov for more information about USGS activities in the Caribbean (Puerto Rico and the U.S. Virgin Islands).
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