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Surface water and groundwater resources
Annual internal renewable water resources (IRWR) are estimated at about 80 million m3 (Table 2). Surface water amounts to about 8 million m3, groundwater derived from infiltrated rainfall to about 74 million m3, while the overlaps between the two (springs and base flow) is estimated at about 2 million m3. Groundwater accounts for by far the largest proportion of the island’s water resources due to the fact that the limestone cap, which covers 86 per cent of the island, is highly permeable, allowing for a well-developed aquifer system (MPDE, 2001).
Most of the rivers in Barbados are dry due to the permeable nature of the coralline karstic limestone. Water finds its way into the aquifers via gullies and sinkholes. As a result there are no perennial rivers which may be used for water supply. In the Scotland district much of the rainfall is lost through runoff to the sea due to the relatively impermeable oceanic rocks. However, at times of intense rainfall the gullies do become flooded, often causing localized flooding downstream (GoB, 2008).
Produced wastewater in 1996 is estimated at 11 million m3 (MPDE, 2001). Barbados is now serviced by two municipal wastewater treatment plants, the Bridgetown Sewage Treatment System (BSTS) and the South Coast Sewage Treatment System (SCSTS), and several package treatment plants. The Bridgetown Sewerage System was commissioned in 1982 and has an average design flow capacity of 9 000 m3 a day (3.29 million m3/year) and services about one eighth of the town of Bridgetown. The South Coast Sewerage System, commissioned in 2003, is an advanced preliminary treatment plant. Planning is at an advanced stage for the construction of a third wastewater treatment facility along the West Coast (GoB, 2008 and BWA, 2014).
Due to high demand of water resources and the low per capita renewable water resources a desalination plant was built in 2000 at Spring Garden, Saint Michael, primarily to augment the public water supply in the event of a prolonged drought as well as to meet additional demand arising from increased economic activity. It consists in a brackish water reverse osmosis desalination plant with a total capacity of 30 000 m3/day (11 million m3/year). The water produced is mixed with and serves to complement the general supply of the Barbados Water Authority (BWA) (BWA, 2014 and GoB, 2008).
There are no important dams in Barbados.