A sedimentation survey of Lago Loíza reservoir was conducted during January 2004 to determine the reservoir water-storage capacity. After a bathymetric survey performed on November 1994, the drainage basin was impacted by Hurricanes Hortense on September 10, 1996, and Georges on September 21, 1998. In addition, dredging was conducted between 1997 and 1999 to increase the storage capacity by about 5.8 million cubic meters to increase the public-supply water safe yield at the Sergio Cuevas Filtration Plant.
The results of the 2004 bathymetric survey indicate that the storage capacity of Lago Loíza reservoir was 17.53 million cubic meters or 3.34 million cubic meters greater than the November 1994 capacity. The long-term reservoir sedimentation rate is about 310,000 cubic meters per year; however, higher annual rates have occurred since the reservoir construction, but these rates are considered short-term, low occurrence, and principally associated with land-use disturbances and extreme runoff events.
The estimated sediment trapping
efficiency of Lago Loíza was as follows:
72 percent in 1994, 78 percent in 1999, and 76 percent in 2004. The Lago Loíza
drainage area sediment yield for the period 1994 to 2004 was 859 cubic meters
per square kilometer per year, about one-and-a-half times higher than the previously
(1990-1994) estimated value of 600 cubic meters per square kilometer per year.
Based on the 2004 bathymetric survey, the continued utility of Lago Loíza as a water-supply reservoir is about 56 more years. Based on the average long-term reservoir sedimentation rate of 310,000 cubic meters per year, however, the storage added by the dredging, which was conducted from 1997 to 1999, will be lost by 2018.
Purpose and Scope
Dam, Reservoir, and Basin Characteristics
Method of Survey
Historical Sediment Accumulation and Effect on Reservoir Storage
Sediment Trapping Efficiency
Sediment Yield and Reservoir Life Expectancy
Summary and Conclusions
1. Lago Loíza, Puerto Rico, Bathymetry, January 2004, Northern Section
2. Lago Loíza, Puerto Rico, Bathymetry, January 2004, Southern Section
Download the Report (PDF, 4.6MB).
The citation for this report, in USGS format, is as follows:
Soler-López, L.R., and Gómez-Gómez, Fernando, 2005, Sedimentation survey of Lago Loíza, Puerto Rico, January 2004: U.S. Geological Survey Scientific Investigations Report 2005-5239, 26 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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