FS 188-96
Fact Sheet
U.S. Geological Survey

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Ground-Water Use from the Principal Aquifers in Puerto Rico During Calendar Year 1990

By Wanda L. Molina-Rivera

ABSTRACT

Puerto Rico has an area of 3,460 square miles (mi²) including the offshore municipalities of Vieques and Culebra. Approximately 30 percent of the area (1,067 mi²) is underlain by alluvial and limestone deposits, which make up the principal aquifers of the islands. These aquifers extend mostly along the islands’ coastal areas. Volcanic rock aquifers of limited extent also may be present locally throughout the east/west trending Cordillera Central mountain range of Puerto Rico and the interior mountainous areas of Isla de Vieques and Isla de Culebra (Gómez- Gómez, 1987). A significant amount of the water used in Puerto Rico during 1990 was withdrawn from aquifers at a rate of 158 million gallons per day (Mgal/d).

For the purposes of this report the principal aquifers of Puerto Rico have been divided into four major aquifer areas, the: (1) North Coast Province; (2) South Coast Province; (3) West and East Coast Provinces, Lajas valley, and the Esperanza and Resolución valleys; and, (4) Interior Province (Caguas-Juncos valley and Cayey valley) (fig. 1). The major aquifer types and the area of coverage in Puerto Rico are shown in table 1.

Puerto Rico has a complex rainfall pattern which is mainly controlled by the orographic effects of the Cordillera Central mountain range, with an average altitude of 2,800 feet (ft) at most peaks and a maximum altitude of 4,400 ft. The Cordillera Central forms a barrier to the Northeast Trade Winds and affects the distribution of rainfall throughout Puerto Rico. Much of the south coast lies in a rain shadow averaging less than 45 inches per year (in/yr) of rainfall, whereas the northern part of the island averages about 80 in/yr.

On a yearly basis, Puerto Rico receives an average of 72 inches of rainfall, of which about 46 inches is lost to evapotranspiration, 23 inches is accounted as surface-water runoff, 1 inch is stored as surface water in reservoirs, 1 inch is withdrawn from coastal aquifers, and 1 inch is ground-water discharge from coastal aquifers to wetlands, estuaries, and the seabed (F. Gómez-Gómez, USGS, written commun., 1996). The offshore islands of Isla de Vieques and Isla de Culebra have a similar rainfall pattern as the south coast of Puerto Rico. A generalized water balance for the island of Puerto Rico is shown in figure 2.

TABLE OF CONTENTS

Introduction
North Coast Province
South Coast Province
West and East Coast Provinces, Lajas Valley, and Esperanza-Resolución Valley
Interior Province
Ground-Water Use
Public Supply
Self-Supplied Domestic and Industrial
Irrigation and Livestock
Mining and Thermoelectric
Selected References

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

Molina-Rivera, W.L., 1996, Ground-water use from the principal aquifers in Puerto Rico during calendar year 1990: U.S. Geological Survey Fact Sheet 188-96, 3 p.