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Scientific Investigations Map 3218

Prepared in cooperation with the Puerto Rico Aqueduct and Sewer Authority

Storage Capacity and Sedimentation Trends of Lago Garzas, Puerto Rico, 1996–2007

By L.R. Soler-López

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Lago Garzas is located in west-central Puerto Rico, about 3.5 kilometers southwest of the town of Adjuntas, in the confluence of the Río Vacas and three other unnamed tributaries (fig. 1). The dam is owned and operated by the Puerto Rico Electric Power Authority (PREPA), and was constructed in 1943 for hydroelectric power generation and municipal water use along the southern coast.

The dam is a semi-hydraulic earthfill embankment lined with boulders, and has a height of 61.57 meters, a top width of 9.14 meters, a base width of 365.76 meters, and a crest length of 227.37 meters; State Road PR-518 crosses the top of the dam. A morning-glory-type spillway is located near the west abutment of the dam at an elevation of 736.12 meters above mean sea level (Puerto Rico Water Resources Authority, 1969). Figure 2 shows an aerial photograph of the Lago Garzas earthfill dam and the morning-glory spillway section. Additional information and operational procedures are provided in Soler-López and others (1999).

During July 17–18, 2007, the U.S. Geological Survey (USGS) Caribbean Water Science Center, in cooperation with the Puerto Rico Aqueduct and Sewer Authority, conducted a bathymetric survey of Lago Garzas to update the reservoir storage capacity and update the reservoir sedimentation rate by comparing the 2007 data with the previous 1996 bathymetric survey results. The purpose of this report is to describe and document the USGS sedimentation survey conducted at Lago Garzas during July 2007, including the methods used to update the reservoir storage capacity, sedimentation rates, and areas of substantial sediment accumulation since 1996.

First posted September 12, 2012

  • Map PDF (1.5 MB) (29 x 29 inches)

For additional information contact:
U.S. Geological Survey
Caribbean Water Science Center
GSA Center, 651 Federal Drive
Suite 400-15
Guaynabo, PR 00965-5703

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.

Suggested citation:

Soler-López, L.R., 2012, Storage capacity and sedimentation trends of Lago Garzas, Puerto Rico, 1996–2007: U.S. Geological Survey Scientific Investigations Map 3218, 1 sheet, available at

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