New USGS Ground Water Atlas Available for Puerto Rico

Today, Rafael Rodríguez, District Chief, U.S. Geological Survey Caribbean District, presented at a meeting of the Commonwealth of Puerto Rico's agencies that work on a cooperative basis an atlas, which covers ground-water resources in Puerto Rico as well as Alaska, Hawaii, and the U.S. Virgin Islands.

Ground water is a vital resource for the people of Puerto Rico, supplying about 29 percent of all freshwater used on the island, but according to a new atlas of ground-water resources by the U.S. Geological Survey, there are indications that this resource has been heavily used.

The latest information on current and historical ground-water conditions in Puerto Rico, as well as the chemical quality of water pumped from aquifers around the Commonwealth, are described in the atlas. It includes previously unpublished information and presents an up-to-date, comprehensive discussion of the ground-water resources of the island.

Puerto Rico's natural ground-water quality is generally good and is suitable for most uses, although hard water and naturally high manganese concentrations are common. The most productive aquifers (geologic formations that are sources of water) are found on the periphery of the island, especially on the north and south coasts. Intensive pumping in aquifers near the coasts can mix sea water with freshwater, making it unfit for most uses. These limestone and alluvial (river deposit) aquifers are very susceptible to contamination. Leaking solid waste disposal sites and careless discharge of industrial wastes has forced many public supply wells to be closed.

The volcanic and sedimentary rock formations that form the island's interior mountain ranges provide significant amounts of water from many domestic wells, but most individual wells have small yields.

Highlights from the Atlas:

• The South Coast Alluvial Aquifer extends from Ponce to Patillas and produces 42 percent of Puerto Rico's ground water.
  

• Alluvium that fills river valleys cut into bedrock, mostly in coastal areas, forms small aquifers that are important locally, providing industrial, municipal and domestic supplies.
  

• The North Coast Limestone aquifer produces about 38 percent of the ground water in Puerto Rico.
  

• The North Coast Limestone aquifer is divided into lower and upper parts, separated by a confining layer. The upper aquifer is easily contaminated through many natural caverns, sinkholes and other openings.
  

• Sea water has intruded as much as three miles inland into the North Coast upper aquifer as a result of ground water pumping.
  

• Ground water demand is increasing as Puerto Rico's economy continues to develop.
  

The USGS atlas summarizes ground-water information for Alaska, Hawaii, Puerto Rico and the U.S. Virgin Islands, and provides a list of published reports on ground water in each area.

Printed in an 18-by-23-inch format with numerous maps and illustrations, this atlas joins 12 others in a series that together provide a source of comprehensive information, written in non-technical language, on the ground-water resources of the nation.

The atlas, entitled "Ground-Water Atlas of the United States, Segment 13, Alaska, Hawaii, Puerto Rico and the U.S. Virgin Islands," by James A. Miller, R.L. Whitehead, and Perry G. Olcott, is published as USGS Hydrologic Investigations Atlas 730-N.

Copies may be Purchased for $4.00 each from the Information Services Branch, USGS, Box 25286, Denver, CO, 80225, telephone 1-800-435-7627 or by fax at (303) 202-4693. There is a $3.50 shipping and handling charge for each order mailed. An abstract and ordering information is available on the Internet at: http://wwwcapp.er.usgs.gov/publicdocs/gwa/

Copies will be also available at the U.S. Geological Survey, Caribbean District Office at the GSA Center, 651 Federal Drive, Suite 400-15, Guaynabo PR 00965-5703.

As the nation's largest water, earth and biological science and civilian mapping agency, the USGS works in cooperation with more than 2,000 organizations across the country to provide reliable, impartial, scientific information to the public, resource managers, planners, and other customers. This information is gathered in every state by USGS scientists to minimize the loss of life and property from natural disasters, contribute to sound conservation, economic and physical development of the nation's natural resources, and to enhance the quality of life by monitoring water, biological, energy, and mineral resources.

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