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Water-Resources Investigations Report

Surface-Water, Water-Quality, and Ground-Water Assessment of the Municipio of Carolina, Puerto Rico, 1997-99

By Jesús Rodríguez-Martínez, Fernando Gómez-Gómez, Luis Santiago-Rivera, and Mario L. Oliveras-Feliciano


In cooperation with the


Water-Resources Investigations Report 01-4267


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To meet the increasing need for a safe and adequate supply of water in the municipio of Carolina, an integrated surface-water, water-quality, and ground-water assessment of the area was conducted. The major results of this study and other important hydrologic and water-quality features were compiled in a Geographic Information System and are presented in two 1:30,000-scale map plates to facilitate interpretation and use of the diverse water-resources data.

Because the supply of safe drinking water was a critical issue during recent dry periods, the surface-water assessment portion of this study focused on analysis of low-flow characteristics in local streams and rivers. Low-flow characteristics were evaluated for one continuous-record gaging station, based on graphical curve-fitting techniques and log-Pearson Type III frequency analysis. Estimates of low-flow characteristics for seven partial-record stations were generated using graphical-correlation techniques. Flow-duration characteristics were computed for the one continuous-record gaging station and were estimated for the partial-record stations using the relation curves developed from the low-flow study. Stream low-flow statistics document the general hydrology under current land and water use. Low-flow statistics may substantially change as a result of streamflow diversions for public supply, and an increase in ground-water development, waste-water discharges, and flood-control measures; the current analysis provides baseline information to evaluate these impacts and develop water budgets.

A sanitary quality survey of streams utilized 29 sampling stations to evaluate the sanitary quality of about 87 miles of stream channels. River and stream samples were collected on two occasions during base-flow conditions and were analyzed for fecal coliform and fecal streptococcus. Bacteriological analyses indicate that a significant portion of the stream reaches within the municipio of Carolina may have fecal coliform concentrations above the water-quality goal 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 at two sampling stations, Quebrada Blasina in Carolina and the Río Grande de Loíza, downstream from the town of Trujillo Alto, indicate that the sanitary quality of Quebrada Blasina is and has generally been poor for more than a decade. The sanitary quality of the Río Grande de Loíza has generally been in compliance with the water-quality goal standard fecal coliform concentrations established in July 1990 by the Puerto Rico Environmental Quality Board.

Geologic, topographic, soil, hydrogeologic, and streamflow data were used to divide the municipio of Carolina into five hydrogeologic terranes. This integrated database was then used to evaluate the ground-water potential of each hydrogeologic terrane. Analysis suggests that areas with slopes greater than 15 degrees have relatively low ground-water development potential. Fractures may be locally important in enhancing the water-bearing properties in the hydrogeologic terranes containing igneous rocks. Potentiometric-surface elevations recorded in piezometers installed in the coastal area during this study were used to define ground-water flow directions in the hydrogeologic terranes composed of coastal plain clastic and limestone units. The resultant potentiometric map indicates that the coastal plain aquifer and streams in the lowland parts of the municipio of Carolina are hydraulically connected. The potentiometric map also indicates that ground-water discharge to the Río Grande de Loíza, downstream from highway PR-3, has been enhanced by dredging of the streambed for sand and gravel. Dredging the streambed may have reduced the thickness of a locally extensive confining clay unit overlying the upper aquifer in this part of the Río Grande de Loíza. The integrated hydrogeologic approach used in this study can serve as an important tool for regulatory agencies of Puerto Rico and the municipio of Carolina to evaluate the ground-water resource development potential, examine ground- and surface-water interactions, and determine the effect of land-use practices on ground-water quantity and quality in the municipio of Carolina.







Chapter A: Surface-Water Resources Assessment of the Municipio of Carolina, Puerto Rico, 1997-99

Purpose and Scope


Results and Interpretation

Low-Flow at Continuous-Record Gaging Stations

Low-Flow at Partial-Record Stations

Flow-Duration Characteristics

Discharge/Drainage-Basin Area

Map Features

Reservoir Sites

Flood-Prone Areas

Public-Supply Water Filtration Plants and Waste-Water Treatment Facilities

Chapter B: Sanitary Quality of Surface Water During Base-Flow Conditions in the Municipio of Carolina, Puerto Rico, 1998-99 Background

Purpose and Scope Methodology

Field-Data Collection

Analytical Techniques

Results and Interpretation

Chapter C: Hydrogeologic Terranes and Ground-Water Resources in the Municipio of Carolina,
Puerto Rico, 1997-99
Purpose and Scope

Results and Interpretation

Summary and Conclusions



  1. Streamflow and bacteriological data collection sites, important hydrologic features, and sanitary classification of streams with drainage to or within the municipio of Carolina, Puerto Rico (PDF 15.0 MB)

  2. Hydrogeologic terranes, potentiometric surface of the alluvial aquifer, selected subbasins, lineament traces, and well locations within the municipio of Carolina, Puerto Rico (PDF 14.0 MB)


Download the Report (PDF, 2.2MB).


The citation for this report, in USGS format, is as follows:


Rodríguez-Martínez, Jesús, Gómez-Gómez, Fernando, Santiago-Rivera, Luis, and Oliveras-Feliciano, M.L., 2002, Surface-water, water-quality, and ground-water assessment of the municipio of Carolina, Puerto Rico, 1997-99: U.S. Geological Survey Water-Resources Investigations Report 01-4267, 45 p., 2 pls.


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