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Potentiometric Surface of the Alluvial Aquifer and Hydrologic Conditions in the Juana Díaz area, Puerto Rico, June 29 - July 1, 2005

By José M. Rodríguez, Luis Santigo-Rivera, and Fernando Gómez-Gómez


In cooperation with the


Scientific Investigations Map 2947


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A synoptic survey of the hydrologic conditions in the Juana Díaz area, Puerto Rico, was conducted between June 29 and July 1, 2005, to define the spatial distribution of the potentiometric surface of the alluvial aquifer. The study area encompasses 21 square miles of the more extensive South Coastal Plain Alluvial Aquifer system and is bounded along the north by foothills of the Cordillera Central mountain chain, to the south by the Caribbean Sea, the east by the Río Descalabrado and to the west by the Río Inabón. Ground water in the Juana Díaz area is in the Quaternary-age alluvial deposits and the middle-Tertiary age Ponce Limestone and Juana Díaz Formation (Giusti, 1968). The hydraulic properties of the Ponce Limestone in the Juana Díaz area are unknown, and the Juana Díaz Formation is a unit of poor permeability due to its high clay content. Consequently, the Ponce Limestone and the Juana Díaz Formation are generally considered to be the base of the alluvial aquifer in the Juana Díaz area with ground-water flow occurring primarily within the alluvial deposits.

The potentiometric-surface map of the alluvial aquifer was delineated using ground-water level measurements taken at existing wells. The water-level measurements were taken at wells that were either not pumping during the survey or were shut down for a brief period. In the latter case, a recovery period of 30 minutes was allowed for the drawdown in the wellbore to achieve a near static level position representative of the aquifer at the measurement point. Land-surface altitude from U.S. Geological Survey (USGS) 1:20,000 scale topographic maps (Playa de Ponce, Ponce, Río Descalabrado, and Santa Isabel) were used to refer ground-water levels to mean sea level datum (National Geodetic Vertical Datum of 1929). In addition to the ground-water level measurements, the potentiometricsurface contours were delineated using hydrologic features, such as drainage ditches and saturated intermittent streams that were considered as aquifer drains and losing streams, respectively.

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


Rodríguez, J.M.and others, 2005, Potentiometric Surface of the Alluvial Aquifer and Hydrologic Conditions in the Juana Díaz area, Puerto Rico, June 29 - July 1, 2005: U.S. Geological Survey Scientific Investigations Map 2947, 1 sheet.

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