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Water Resources of the Caribbean

Lago Loíza at Damsite - 50059000

Pedestrians walking along top of Río Loíza Reservoir walkway, looking toward right bank.  USGS photo archive, January 25, 1958. Pedestrians walking along top of Lago Loíza Reservoir dam in the 1950's.  Photo from USGS archive.
Lago Loíza is located in the municipio of Trujillo Alto.  Carraizo Dam, which impounds Lago Loíza, was constructed in 1953 by the Puerto Rico Aqueduct and Sewer Authority (PRASA).  This reservoir is located about 13.5 miles (21.7 kilometers) upstream of the outlet of the Río Grande de Loíza to the Atlantic Ocean.   Originally, the reservoir was constructed to generate hydroelectricity (3,000 kilowatts), but now the reservoir is used as a public water-supply source exclusively

Real-time Reservoir Level

Real-time resevoir level graph updated hourly with the exception of emergency transmissions which are at 5 minute intervals. To view real-time data, follow the link below.

Lago Loíza at Damsite - 50059000.

Lago Loíza has a drainage area of about 206.0 square miles (331 square kilometers).  Originally, the reservoir had a water storage capacity of 21,735 acre-feet (26.8 million cubic meters), but by 1994 the capacity had been reduced by sediment infilling to.  During 1995, the Sergio Cuevas Filtration Plant produced 89 million gallons per day (337 million liters per day) of potable water to supply more than 750,000 persons within the metropolitan area that includes the municipios of San Juan, Trujillo Alto, Caguas, Gurabo, and portions of San Lorenzo, Canóvanas, Loíza and Río Grande.

Loíza Basin Map

Click onLake symbol in the basin map for combined real-time reservoir and rainfall information.

50059000 Loíza Basin Map



Chart correlating lake level elevation to water volume: Lago de Loíza at Damsite - 50059000

The U.S. Geological Survey, in cooperation with PRASA, has produced a number of reports regarding effects of sediment infilling on storage capacity of Lago Loíza, including:

Webb, R.M.T., and Soler-López, L.R., 1997, Sedimentation history of Lago Loíza, Puerto Rico, 1953-94: U.S. Geological Survey Water-Resources Investigations Report 97-4108, 18 p., 9 pls.

In addition, the U.S. Geological Survey, in cooperation with local government agencies, has produced a number of reports regarding the effects of sediment infilling on the storage capacity of principle water-supply reservoirs of Puerto Rico.  The results of these surveys are summarized in "Sedimentation survey results of the principal water supply reservoirs of Puerto Rico,"

These reports can be purchased at a nominal cost by contacting Information Desk at the U.S. Geological Survey, GSA Center, 651 Federal Drive, Suite 400-15, Guaynabo, PR 00965, 787-749-4346 ext. 296.  Please contact Water-Use Information, 787-749-4346 ext. 259, if you have other questions regarding water supply in Puerto Rico.

The table below shows the relationship between reservoir level and available water. This information is presented in graphical format in the figure above. Note that an acre-foot is a volume of water that would cover an acre (43,560 square feet) to a depth of 1 foot.

Lago Loíza - 50059000

Reservoir elevation in Volume in
meters feet million cubic
41.14 135 14.19 11,504
41 135 13.80 11,188
40 131 11.37 9,218
39 128 9.19 7,450
38 125 7.23 5,861
37 121 5.48 4,443
36 118 3.91 3,170
35 115 2.72 2,205
34 112 1.79 1,451
33 108 1.08 876
32 105 0.58 470
31 102 0.30 243
30 98.4 0.18 146
29 95.1 0.09 73.0
28 91.9 0.04 32.4
27 88.6 0.02 16.2
26 85.3 0.004 3.24
25 82.0 0.001 0.81
24 78.7 0.0003 0.24
23 75.5 0.00 0.00

Lago de Cidra Reservoir covered with water hyacinths.  Photo by U.S.G.S., Orlando Ramos, August 1998
View looking up-stream toward Carraizo Dam, under drought conditions .  Photo by Matthew Larsen, USGS

Lago de Loíza Reservoir during Hurricane Hortense. Photo by Matthew Larsen, USGS
Lago de Loíza Reservoir during Hurricane Hortense. Photo by Matthew Larsen, USGS


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