Living under Tobago’s Drought

The level of infrastructure development in Tobago and the immediate prospects for improvement are critical to the overall development of the Tobago economy. The specific areas of infrastructure that have to be addressed are water supply; wastewater treatment; transport by land, sea and air; electricity, and information and communications technology. In view of the emphasis being placed on tourism development as a major plank of economic development, the immediate will be on the water supply situation.

In the past, project activity on the water supply system in Tobago placed little emphasis on the development of new water sources although the need was recognised for expediting the Richmond water project and expansion of the water resources development programme.
Rather, the focus was on the distribution system, in particular, the extension and replacement of mains which were seen as a more pressing need. Despite this emphasis, the water distribution infrastructure continued to be very deficient with leakage ranging from 50% to 80%, which translates into considerable losses. In effect, the planning of the improvement of the water distribution system was seriously defective and winning additional water was relegated to a lower priority. No water in dry or rainy seasons

The data on the supply of potable water show that production stands at 9 million gallons per day, (mgd) which is the approximate equivalent of 40,000 cubic metres per day (m?), which serves all users domestic, commercial and industrial.  This supply, made up of six mgd (28,000 m?) from surface water and three mgd (13,000 m?) from wells, has been relatively constant since 1997. The critical problem is that supply is generally deficient in both the dry and rainy seasons but for different reasons.  In the dry season, supply becomes a function of rainfall to feed the dams and replenish the ground water while in the rainy season, turbidity affects the dams causing a reduction of service because of temporary shut downs. This situation is reflected in WASA’s data which indicate that, in the critical periods, surface water production drops to 3.2 mgd (14,477 m3) and ground water to 2.6 mgd (12,000 m?), which is an overall reduction of 35% .

Improvement works are being undertaken at the existing water sources as well as in the distribution network which have enhanced the water supply situation but the desired level of service has not been achieved. The result is that Tobago has a current demand/supply deficit of approximately 3.0 mgd at the critical periods. In order to reduce this gap, it was proposed to construct a 1.0 mgd desalination facility at Courland with an operating cost estimated at $ 2.8 million per year. It was further recommended that this facility be upgraded to an installed capacity of 3.0 mgd for the longer term.

The data for 2002 show that natural water resources availability and actual abstraction from river sources accounted for approximately 70% of the total water captured during that year.  With respect to additional water-producing potential within the island, the Sandy River and Louis D’or Rivers have been identified as surface water systems that may have additional potential. WASA has estimated the quantity of water that can be accessed from these rivers and the associated costs are estimated at $23.1 million.  While this option cannot produce enough water to satisfy future requirements, it may provide necessary temporary respite and narrow the demand/supply gap.

From the ground up
The other major source of water is the groundwater systems which include the traditional alluvial and gravel aquifers but these are producing at levels approaching their potential yield.  However, the existence of deep-seated bedrock aquifers underlying these traditional systems has been proven in a hydro geological study (Tobago Groundwater Study and Well Development Programme, Earth Technologies Inc 2000). 

The study inferred that there is a safe yield of approximately 35 mgd within these aquifers, of which 3.0 mgd have already been developed as a direct consequence of the study. Further, 16 “favourable zones,” where the balance of the untapped potential may exist were identified. Potable water for the south-western part of Tobago is obtained from four surface water sources and one groundwater source. The Crown Point, Buccoo, Diamond and Plymouth area is supplied from the Courland water treatment works which draws water from the Courland River close to Plymouth.  Most of Scarborough, Lambeau, Whim and areas as far east as St George receive water from the Hillsborough water treatment works, Hillsborough West and Greenhill intakes.