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Trinidad and Tobago
Surface water and groundwater resources
The mean annual rainfall in the country is 2 200 mm (Table 2). Long-term annual renewable surface water resources are estimated at 3 740 million m3, of which 3 600 million m3 in Trinidad and 140 million m3 in Tobago. Long-term average annual renewable groundwater resources are estimated at 614 million m3, of which 545 million m3 in Trinidad and 69 million m3 in Tobago. Considering an overlap between surface water and groundwater resources of 514 million m3, the total Internal Renewable Water Resources (IRWR) are estimated at 3 840 million m3/year.
There are 55 catchment areas in Trinidad and 15 in Tobago. Large-scale development of surface water has been limited to four rivers in Trinidad and Tobago. These are the Caroni and Oropouche rivers in the Northern Basin and the Navet river in the Central Range in Trinidad and the Hillsborough river in Tobago, which is the principal source of supply for Scarborough and southwest Tobago.
Groundwater is found throughout most of Trinidad. The major groundwater areas include the Northern Valley aquifers in alluvial deposits at Chaguaramas, Tucker Valley, Diego Martin and Port of Spain; the alluvial fan deposits at El Soccorro, Valsayn, Tacarigua and Arima; the artesian aquifers in the Sum Sum and Durham sands; the reef limestone’s of the Central Range; and sands in the Erin, Morne L’Enfer, and Mayaro formations of Southern Trinidad.
There are four surface water reservoirs, three in Trinidad (Caroni-Arena, Navet and Hollis) and one in Tobago (Hillsborough), with a total capacity of 72 million m3. The largest of these reservoirs is the Caroni - Arena dam in the Caroni river, commissioned in 1981. It has a capacity of 46.6 million m3 and supplies water to areas of central Trinidad. The Navet reservoir, commissioned in 1962 and expanded in 1966 and 1976, has a total capacity of 19.1 million m3 and was designed to supply San Fernando and other outlying districts including Rio Claro, Princes Town, Moruga and Gasparillo. The Hollis reservoir on the Quare river, commissioned in 1936, has a total capacity of 4.75 million m3 and supplies Arima, Port of Spain and other areas of north Trinidad. The Hillsborough reservoir, commissioned in 1952, has a maximum storage capacity of 1.02 million m3. Water from the reservoir serves areas such as Mt. St. George, Concordia, Whim, Mary's Hill, Union and Les Coteaux (WASA, 2015).
Private water users have constructed and operate small reservoirs, mainly in south Trinidad, but no data about their capacity were available.