Many of the CARICOM Member States face severe constraints in terms of both the quality and the quantity of freshwater because of their small size and particular geological, topographical and climatic conditions. The scarcity of water resources is a limiting factor for economic and social development in CARICOM (Caribbean Environmental Outlook, 2005). This is even more the case for low-lying coral-based islands, where there are limited supplies of groundwater and which are protected only by a thin permeable soil. Water supply was identified as a priority by the 1978 Caribbean Environmental Health Strategy and the First CARICOM Ministerial Conference on the Environment (CARICOM 1989).
Water Resources
Groundwater, rainfall, surface reservoirs and rivers are the main sources of freshwater in many CARICOM member states. The majority of the member states are reflective of the following four country examples:
In Antigua and Barbuda for example, there are no perennial water sources in the country. The total average rainfall for both islands is estimated at 453 million m3/year and Internal Renewable Water Resources (IRWR) about 52 million m3/year. At present the country's agricultural and municipal (domestic and commercial) water demands are being met by two desalination plants (total capacity 3.3 million m3/year); three surface dams, numerous small ponds and 5 well fields (total capacity 2.8 millions of m3/year). The small ponds are used primarily for agriculture and many of the reservoirs are used for both agricultural and municipal uses. During drier months irrigation is restricted to a very limited surface due to shortfall in surface and groundwater yields, and most surface water storage is diverted to municipal supply. On the other hand, Barbuda's topography and geology are not well suited to dam construction (AQUASTAT).
In Barbados, the Annual Internal Renewable Water Resources were estimated in a 1997 Water Resources Study to total about 82 million m3. Groundwater derived from infiltrated
rainfall accounts for 73.9 million m3; surface water amounts to 5.8 million m3; springs 2.0 million m3 and direct runoff to the sea 0.5 million m3(AQUASTAT).
The mean annual rainfall is 2 200 mm for Trinidad and 1 900 mm for Tobago. According to a study conducted in 1998, available surface water resources were estimated at 3 600 million m3/year for Trinidad and 136 million m3/year for Tobago. The groundwater safe yield for both islands was estimated at 107 million m3/year. Large-scale development of surface water has been limited to four rivers in Trinidad and Tobago. There are five surface water reservoirs (four in Trinidad and one in Tobago) with a total capacity of 75 million m3. Private water users have constructed and operate small reservoirs, mainly in south Trinidad, but no data about their capacity were available. 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.
Estimates of surface water resources are not available over all of Guyana: there are data available from the three main drainage basins of Essequibo, Demerara and Berbice (Table 9).
Table 10: Characteristics of the main river basins in Guyana.
Drainage basin Station Surface area (km2) Discharge (km3/y) Specific discharge (m3/s/km2)
Plantain 66 600 66.96 0.0319
Apaikwa 14 000 23.98 0.0543
Essequibo
Kamaria 53 500 35.52 0.0211
Demerara Great Falls 2 460 2.32 0.0299
Berbice Itabru 5 100 1.60 0.0099
The groundwater system comprises three aquifers. A small amount of the copious supplies of surface water which run off is trapped by a long low earth embankment to form large shallow dams locally known as "conservancies". The conservancies are located in the "backland" or upper stream catchment areas and comprise water-retaining embankments and structures.
Water Use
Water demand which has increased over the past 30 years as a result of population growth and rapid urbanization is exceeding the natural supply capacity. At current population levels, the available water supply in some of the member states is significantly below the international limit of 1 000 m3 per capita per year below which a country is classified as ‘water scarce’ (Government of Barbados 2000). This limit places Antigua and Barbuda (800 m3 per capita), Barbados (301 m3 per capita), and St Kitts and Nevis (621 m3 per capita) in the category of water-scarce countries (FAO 2003b).
Agriculture is the largest consumer of water in the CARICOM, consuming over 90 per cent of the total water used in Guyana, Haiti and Suriname. Industrial consumption of total
renewable water resources exceeds other uses in Barbados, while domestic consumption is the primary use in others such as Trinidad and Tobago (UNEP, 2005).
The demand for water in many of the islands The Bahamas is met primarily by extraction from shallow freshwater lenses. Extraction of freshwater is very high on some islands in this archipelago as a result of the demands of the local population and the tourism industry. This is especially the case on New Providence, where inadequate freshwater resources necessitates the import of water from Andros Island. Nationally, the high water deficit has led to desalination of seawater by reverse osmosis (Government of the Commonwealth of The Bahamas 2001).
Management Issues
Many of the low limestone islands of the Caribbean such as Anguilla, Antigua and Barbuda, Grenada, and Barbados, are heavily dependent upon rainfall as the freshwater recharge source. The situation is critical for these countries where rainfall seasonality is very pronounced (UNEP, 2005). For example, in Barbados groundwater recharge is restricted to the three wettest months of the year; with only 15–30 per cent of annual rainfall reaching the aquifers (Jones and others 1998). Of critical importance, much of the rainfall in the region is strongly associated with tropical depressions and storms, therefore any change in the occurrence of these events will have an impact on the water supply of many CARICOM countries (see Gray 1993; Nurse and others 1998 in UNEP, 2005). In Dominica, for example, reduced flows in the Castle Comfort, Roseau, Layou and Geneva rivers have raised national concerns, since these rivers are the main source of potable and irrigation water on the island The declining flows have been well correlated over the last few decades with extended periods of drought (Government of the Commonwealth of Dominica 2000 in UNEP, 2005).
continues (Martin and Bruce 1999). Saltwater intrusion into the freshwater lenses from over extraction is also threatening freshwater supplies in the Bahamas and Barbados.
The Caribbean Environmental Outlook (2005) reported recent increases in salinity levels for several coastal aquifers in Trinidad and Tobago, attributed mainly to rapid draw-down exacerbated by sea-level rise. The impact of climate change on water supply is also a critical issue for sustainable development in CARICOM. Shrivastava (1997) suggested that annual precipitation would increase by approximately 6 per cent in the Western Caribbean and decrease by 4 per cent in the Eastern Caribbean as a result of climate change. Prolonged and heavy wet seasons and more severe and longer droughts during the dry seasons are predicted.
The vulnerability of water resources to climate change has been demonstrated in Grenada where the droughts of 1984 and 1992 caused freshwater losses of 20 per cent and 40 per cent, respectively. Recovery from these losses can take many years (Government of Grenada 2001). This situation is expected to become worse with the increase in freshwater demands due to population growth and the expansion of tourism. In several countries, the adverse implications of climate change on water resources will be compounded as growing populations move into marginal areas with very limited water supply. Insufficient quantity and quality of water, particularly potable water, is correlated with increases in waterborne diseases, particularly when people seek alternative sources, which may be of poor quality. Increases in the incidence of heat-related illnesses also occur during periods of drought and elevated temperatures (Government of Jamaica 2001).
One of the targets of the Millennium Development Goal 7 requires countries to ‘halve, by 2015, the proportion of people without sustainable access to safe drinking water and sanitation’. It will be difficult for many Caribbean countries to meet this goal, considering their already high coverage rates (over 82 per cent for drinking water and up to 97 per cent for sanitation, with the exception of Haiti), as well as the deteriorating condition of remaining freshwater resources (UNDP 2004).
Deforestation and inappropriate land use practices in watersheds have impacted upon groundwater recharges and water retention capacities of soils. In addition, ineffective maintenance and replacement of infrastructure give rise to transmission losses as high as 50 per cent in some countries.