Water Resources of the Caribbean
Caribbean Water Science Center Science Plan 1999Introduction
Severe water rationing has been implemented three times during the 1990's in Puerto Rico. At the same time, significant agricultural losses, valued in the $100's of millions have occurred. A drought in 1994-95 affected more than one million people in the San Juan metropolitan area who endured a regimen of water rationing that lasted for six months in which sections of San Juan had their water-distribution networks shut off on alternate days. Hurricanes, or other tropical disturbances, are the dominant type of high-magnitude storms affecting Puerto Rico and the U.S. Virgin Islands. Hurricanes Hugo, Marilyn, Hortense, and Georges have all struck the islands in the last 10 years. Hurricane rainfall totals during the 20th century have averaged 300 to 800 millimeters (mm) during a 24 to 48 hour period, and most of the peak discharge of record for the surface water gaging station network have been associated with hurricanes. Puerto Rico’s population density is among the highest in the world, about 440 people per square kilometer. The U.S. Virgin Islands are also densely populated with more than 300 people per square kilometer. The population growth rate in Puerto Rico shows a general decline since 1970, being 2.8 percent per year (%/y) between 1970 and 1980, and 1.4 %/y between 1980 and 1990. However, the population has increased from 2.7 million in 1970 to 3.8 million in 1995.
During this period (1970 to 1995), water use has risen at an average annual rate of 1.6 %/y from 1.5 million cubic meters per year (m3/y) in 1970 to 2.1 million m3/y in 1995. In addition, surface-water storage has been reduced by the high sediment loads of river systems in which the Puerto Rican reservoirs have been constructed. For example, the annual rate of storage loss at the Lago Loíza reservoir, which supplies about half of the public water supply to the San Juan Metropolitan area, was 1.3 percent, between 1953, when the reservoir was impounded, and 1994. The sedimentation has reduced the reservoir’s firm yield from about 50 million gallon per day (Mgal/d) to about 35 Mgal/d.
One of the most critical issues is water availability: both Puerto Rico and the U.S. Virgin Islands face difficulties for supplying their future generations. Although the situation for Puerto Rico is vastly different from that of the smaller Caribbean islands, it has a water shortage stemming from rapid urban development, increased consumption by all economic sectors, deteriorating water quality, and aging infrastructure. To solve some of these problems, the Commonwealth government has recently built a major 70-kilometer-long pipeline to supply communities along the north coast and the San Juan Metropolitan area and begun several additional water infrastructure projects in other parts of the island. The U.S. Virgin Islands lack surface water sources and must rely on desalinization of seawater for their main water supply. Their limited ground-water resources and coastal environment are under constant danger from pollution from industry, septic and leaking underground storage tanks, and saline-water intrusion. These two different realities provide for unusual opportunities for applied hydrologic research in which the USGS Caribbean District should play a major role. Throughout the 42 years that the USGS has maintained a continuous presence in Puerto Rico and the U.S. Virgin Islands, many studies have been completed for lakes, watersheds, and individual river basins. We should now begin to emphasize on long-term hydrologic monitoring and interpretive studies with potential applicability on a broader scale to other tropical areas and more specifically to the Caribbean and Central America. The USGS has collected many years of useful data that need to be interpreted at the various scales to give the full regional perspective on water-resource issues in the Caribbean. The Caribbean District has a talented staff of scientists, engineers, and technicians that can conduct the necessary studies. The Science Plan for the Caribbean District has been prepared following the issues presented in the Southeastern Region, “Planning for 2003-2008 in the Southeastern Region of the Water Resources Division.” The present level of understanding of each hydrologic and program support category is briefly presented followed by a list of information needs and deficiencies and the Caribbean District's desired scientific direction for its hydrology program. The strategies and goals presented in this document are expected to be valid for approximately five years, but will be reassessed every two years so as to maintain their relevance and reflect as accurately as possible the Caribbean District program objectives. The USGS, Caribbean District is in a privileged position to help water resources managers, inform the general public, and encourage wide participation in water-management decisions in the Caribbean region. To assist in this process, the USGS has established an integrated surface water, ground water, and water-quality monitoring network. The Caribbean District is using GIS technology and dual-language fact sheets to disseminate the data to the general public. Some of this data is now available to the public on the internet. The network consists of 129 hydrologic data-collection sites equipped with satellite telemetry instrumentation. Data gathered in past years has been used by the Caribbean District to establish the long-term yield of major watersheds and reservoirs in Puerto Rico and build ground-water models for major aquifers in both Puerto Rico and the U.S. Virgin Islands. Flow duration and flood frequency studies have been conducted and updated studies will be published soon. These studies are essential in managing the water resources of the islands. Real-time simulation of river flows during storm events has been conducted for the Río Grande de Loíza and its major tributaries. Additional basins like the Río Grande de Arecibo, Río de la Plata, and the Río Grande de Manatí should be modeled in the future. |
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U.S. Department of the Interior |
U.S. Geological Survey
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Jan 18, 2008, 13:57
Several rainfall deficient periods in the 1990’s and an aging public water-supply infrastructure have seriously affected the ability of our cooperators to deliver a continuous supply of potable water to the 4 million people living in Puerto Rico and the U.S. Virgin Islands. In addition, during this decade more hurricanes and droughts have impacted the islands than during the previous 50 years.
During the winter and spring of 1997-98, more than two hundred thousand people in northwestern Puerto Rico experienced severe rationing of public-supplied water as water level in their principal reservoir, 
This rainfall deficit may be an indication of a regional drying trend that makes large populations in the West Indies vulnerable to water shortages. The total population of the 24 island nations in the West Indies is 37 million. The critical water shortages that have occurred in Puerto Rico, the third most populous island in the West Indies, provide an example of the impact of water resource shortages on regional population.
In addition, these storms have typically been responsible for the largest amounts of suspended sediment transport documented in Puerto Rico. For example, sediment transport associated with Hurricane Hortense, September 1996, measured at the 
These high population densities combined with complex geology, high relief (1,338 meters on Puerto Rico), and the short distance (maximum of 35 kilometers) between the insular hydrologic divide and the sea, create and drive many of the water-resources issues that the Caribbean District is facing in the next millennium. This brief description of some water-resource related problems provides the setting for USGS Caribbean District research and program direction in the future.
It includes streamflow, lake-stage, ground-water, rainfall, and meteorological stations. The Ground Water Site Inventory includes data from over 5,000 wells in Puerto Rico and 1,000 wells in the U.S. Virgin Islands.