The Lago Guayabal dam, located in the municipality of Villalba in southern Puerto Rico, was constructed in 1913 for irrigation of croplands in the southern coastal plains and is owned and operated by the Puerto Rico Electric Power Authority. The reservoir had an original storage capacity of 11.82 million cubic meters and a drainage area upstream of the dam of 112 square kilometers. Sedimentation has reduced the storage capacity to 6.12 million cubic meters in 2001, which represents a storage loss of about 48 percent. However, the actual sediment accumulation in the reservoir during the 88 years is greater, because some sediment removal was conducted between 1940 and 1948 by dredging and sluicing. This report summarizes the historical data from a 1913 land survey and eight bathymetric surveys conducted between 1914 and 2001, and the relation of high sedimentation to agricultural land practices within the Lago Guayabal basin and six major hurricanes which made landfall on the island.
The reservoir had an area-normalized sedimentation rate of about 1,863 cubic meters per square kilometer per year between 1913 and 1936 from a 112 square kilometer basin. In 1972, a new dam upstream along the Río Toa Vaca impounded runoff from 57.5 square kilometers, and sediment transport to Lago Guayabal was reduced. A comparison of bathymetric survey results between 1972 and 2001 indicates an area-normalized sedimentation rate of 1,120 cubic meters per square kilometer per year or about 60 percent of the rate between 1913 and 1936. The significant reduction (almost half) of the sedimentation rate after the Toa Vaca dam was built may indicate that erosion susceptibility of the Río Toa Vaca watershed is about twice that of the Río Jacaguas watershed impounded by Lago Guayabal.
Abstract
Introduction
Dam, Reservoir, Basin Characteristics, and General Land-Use History
Method of Survey
Field Techniques
Data Processing
Previous Bathymetric Surveys, Storage Capacities, and Sediment Accumulation
Trapping Efficiency
Sediment Yield
Summary
References Cited
1. Lago Guayabal, Puerto Rico, Bathymetry, December 2001 (183KB)
The citation for this report, in USGS format, is as follows:
Soler-López, L.R., 2003, Sedimentation History of Lago Guayabal, Puerto Rico, 1913-2001: U.S. Geological Survey Water-Resources Investigations Report 03-4198, 28 p., 2 pls.
Please visit http://pr.water.usgs.gov/ for more information about USGS activities in the Caribbean (Puerto Rico and the U.S. Virgin Islands).
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