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RESERVOIRS AND DAMS
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Hillsborough Reservoir
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OVERVIEW
The Water And Sewerage Authority is pleased to welcome you to Hillsborough Reservoir.
Standing 100 feet above sea level, Hillsborough has a rustic beauty that blends with its design from a bygone age.
The reservoir has a maximum storage capacity of 225 million gallons and an elegent design spillway provides a safety outlet when the reservoir is too full.
Hillsborough remains the largest and most reliable source for potable water in Tobago, supplying a water treatment facility with a daily output of 1.7 million galons.
HISTORY
Back in the 1940's the world was upturned in the throes of the Second World War. In the quiet uplands of Tobago, the landscape was also scattered and greatly altered, but for a different purpose. Stone was being quarried, a river was blocked, the trees of the forest were felled, and a whole area flooded, with the impounded waters of the Hillsborough East River. While war rages elsewhere, a new water source for Tobago was being captured.
In 1944, the first excavations began and by May 1952, the Hillsborough Dam and Reservoir were proudly commissioned, along with its treatment plant by His Excellency Sir Hubert Elvin Rance, then Governor of the Colony of Trinidad and Tobago.
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TREATMENT PROCESS
Water passes from the reservoir for treatment through one of the three draw off points that are situated at different levels in the reservoir. Sometimes the reservoir itself becomes too full and there is the danger of the water flowing over the dam well. To prevent this, a spillway was built, to divert excess water from the reservoir to a safety outlet channel.
The spillway at Hillsborough has a particularly elegant design running in a series of converging stepways, down the gradient of the land. As the reservoir itself stands 36.5 meters (100 feet) above sea level, water passes from it and through the treatment plant by gravity flow.
The raw water from the reservoirs passes through two strainers that clear the incoming water of large debris, such as branches and twigs and leaves then to the chemical house.
Here activated carbon is added to rid the water of bad tastes and smells. Aluminum sulphate (alum) is also added to make the suspended particles of silt and mud carried in the water coalesce in large and heavier particles that sink to the bottom of the sedimentation (or settling) basins. The water passing through the sedimentation basins gets clearer as its muddy contents settle out.
The settled water leaves the basins by a main that transports it to the filter complex. The water is then filtered through layers of sand and gravel, a process, which removes fine particles still in the water. In the two narrow galleries overlooking the filters on the eastern and western sides, there are valves, which allow for the filters to be emptied and which provide for them to be cleaned by air scouring and washouts, from time to time.
The final stage of the water treatment process is the addition of lime to counteract the acidity of the water and the injection of chlorine to destroy any disease-causing bacteria.
The chlorine also protects against any contamination that may occur while the water is being distributed.
Hillsborough provides the largest and most reliable supply of potable water in Tobago.
LOCATION
Off the Windward Road in MT. St. George
COMMISSIONED
May 1952
DAILY OUTPUT
9090 cubic meters (M3/D)
AREAS BENEFITING
The main pipeline branches at Mason Hall, from which point some of the water is taken to Government House Road and up to the service reservoir on 'The Fort'. Another main branches at Greenhill, carrying its supply by a different route via Mt. St. George, Hope and Bacolet to Scarborough and the 'The Fort'. The intervening areas are served along the way.
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View Hillsborough Capacity (Historical)
View Hillsborough Rainfall Data
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