U.S. Geological Survey Studies Reveal that Sediment is Filling Many Water-Supply Reservoirs in Puerto Rico

During the past two decades, the U.S. Geological Survey Caribbean District, in cooperation with the Puerto Rico Electric Power Authority and the Puerto Rico Aqueduct and Sewer Authority, has conducted a number of surveys on the principal water-supply reservoirs to determine how fast water holding capacity is being lost by infilling of these reservoirs by sediments. On February 23, Hydrologist Luis Soler-López of the U.S. Geological Survey presented a summary of results of these lake surveys at the Sixth Caribbean Islands Water Resources Congress that was held last week in Mayagüez.

Soler-López provided evidence that the principal reservoirs of Puerto Rico are rapidly losing their water storage capacity because of high rates of sediment influx and accumulation. The factors that promote sedimentation in the reservoirs include land use, steep drainage basin slopes, and most importantly, high rainfall magnitudes and frequencies, like the ones generated from major tropical disturbances. The storage capacity losses for 14 reservoirs studied range from 12 to 81 percent, averaging 35 percent. Soler-López showed that recent construction of new reservoirs has not actually increased water-supply capacity, but has only partially offset the loss of water-supply capacity caused by sediment infilling of the existing reservoirs. Soler-López demonstrated that large hurricanes, such as Hortense in 1996 and Georges in 1998, caused very substantial storage capacity loss in many reservoirs.

Soler-López’s presentation has been published on CD by the Puerto Rico Water Resources and Environmental Research Institute (University of Puerto Rico at Mayagüez), and copies are available upon request from the U.S. Geological Survey at (787) 749-4346 extension 221.

The USGS is 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 resource managers, planners, and other customers. The information is gathered in every state by USGS scientists to minimize the loss of life and property from natural disasters, to contribute to the conservation and sound 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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