Oficina Regional de la FAO para América Latina y el Caribe |

IRRIGATION IN TRINIDAD & TOBAGO

Climate

The country has a tropical climate and receives abundant rainfall ranging from 1 200 mm to 3800 mm in Trinidad and from 1 200 to 2 800 mm in Tobago. There are two seasons: dry, from January to May; and wet, from June to December, with a secondary dry season or Petit Carême occurring in September and October. Approximately 70-80% of annual rainfall occur during the wet season. Annual temperatures range from 26 to 30 oC. Temperatures in Tobago are somewhat lower than in Trinidad with a marked decline of about 4oC in the Main Ridge area.

Water Resources

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. These are the Caroni and Oropuche Rivers in the Northern Basin, 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. There are five surface water reservoirs (four in Trinidad and one in Tobago) with a total capacity of 75 million m3. The largest of these reservoirs is the Arena dam (Caroni River), with a capacity of 46.6 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.

Water withdrawal

Water withdrawal was estimated at 173 million m3/year in 1997, about 5% of the available surface resources. Domestic withdrawal was 118 million m3/year, 45 million m3/year for commercial and industrial use and about 10 million m3/year for agriculture (Figure 1). The demand is expected to increase with improved public water supply, population growth and development of the oil sector.

Figure 1. Water withdrawal by sector in 1991.
Total water withdrawal: 266 million m3.

The entire population (rural and urban) has access to domestic water supply. About two-thirds of Trinidad's current water supply are taken from groundwater aquifers.

Irrigation and drainage development

The scarce rainfall during the dry season and the Petit Carême make irrigation necessary for crop production in some parts of the country. Improvements in drainage and flood control measures are also needed to enable wet season cultivation in some areas. Investments in water management infrastructure for irrigation and drainage tend to be expensive and, given that most crops are only feasible during the dry seasons, these investments are only justifiable to produce high value crops.
According to a land capability survey carried out in 1974, irrigation potential area considering soil suitability for irrigation (slope lower than 10% and alluvial and terrace lands) was estimated at approximately 102 000 ha. The Basic Agricultural Studies (1992) stated that irrigation is a key element in the agricultural development of the country, and a general target of increasing area under irrigation to 30 000 ha over a period of 20 years was suggested.
The total area under irrigation was 3 634 ha in Trinidad and 78 ha in Tobago in 1981 (1982 Agricultural Census), representing just 7% of the island's total cultivated area at that time. Although no systematic information regarding irrigated areas for the country as a whole is available since the 1982 Agricultural Census, estimates consider that the area under irrigation has increased marginally since 1981. Actual irrigated area in the 1998 dry season was estimated at 3 041 ha, distributed as follows: Caroni (1 739 ha), South Oropuche (720 ha) and Nariva (147 ha), with small-scale irrigation in South Trinidad (435 ha).
However, it should be noted that as the 1997 wet season was relatively dry, these figures will most probably reflect the lower ranges of the extent of irrigated area. Cropped and irrigated areas differ largely from the wet to the dry season.

The largest irrigation system is the Caroni system constructed to serve the surrounding rice fields. This system diverts water from the Caroni River and distributes the water over an area of about 1 200 ha.
Irrigation in Trinidad involves small diversions from creeks and streams at works built by private individuals. Irrigation by gravity flow is also practised in the floodplains. This type of irrigation takes place on a small scale in the Guanapo, Aripo and San Juan Rivers, and on a large scale in the Caroni and South Oropouche Rivers.
In terms of irrigation techniques, surface irrigation systems (furrow, basin) were predominant in 1981 accounting for 78% of the area under irrigation, followed by sprinkler irrigation (19%) and localized irrigation (3%). In Tobago, sprinkler irrigation was prevalent, occurring on 75% of the area under irrigation, followed by furrow irrigation (22%).
No systematic data are available on irrigated crops. However, paddy rice, root crops and vegetables (pumpkins, cucumber, tomatoes, hot and sweet peppers, cabbage, cauliflower, lettuce, beans, watermelon, etc.) are the major crops grown under irrigation. Little or no irrigation occurs during the dry season on hillside vegetable farms, sugar cane, tree crops, coffee, citrus and cocoa.
Drainage infrastructure and flood control structures are needed to allow cropping in the wet season in the lowlands. The drained area under irrigation was reported to be 776 ha in 1998.
Water quality is deteriorating especially in urban and industrial areas and the discharge of agricultural pollutants such as herbicides and pesticides is of major concern.

Trends in water resources management

The Food and Agriculture Policy White Paper (MALMR, 1995) described the policies and strategies for the agricultural sector. This policy includes, among others, the promotion and enhancement of domestic food and nutrition security, facilitating an increase in foreign exchange earnings from exports, promoting private investment in the sector, promoting development of aquaculture and infrastructure support on the establishment of water management systems and promoting on-farm irrigation infrastructure.
Irrigation, mainly used for paddy rice and vegetables so far, is seen as one of the means to increase rice cropping intensity, improve yield of sugar cane and diversify the production towards exportable off-season crops such as vegetables, citrus, tropical fruit trees or cut flowers. The areas with plans for irrigation development cover about 3 200 ha and are mainly concentrated in the Couva basin (2 000 ha), Nariva basin (400 ha) and Ortoire basin (400 ha) in Trinidad and 216 ha in Tobago. However, as adapted in the Water Management Component of the Agricultural Investment Programme, the bottom-up approach that will be used will most probably come up with more realistic and well-founded figures on irrigation potential.
In any case, farmers' demand for public investment in water management assigns a higher priority to drainage than to irrigation. Furthermore, the poor quality of the water presently being used in existing irrigation schemes and the widespread excessive use of pesticides and chemicals undermine the safety of food crops being consumed and represent a threat to the sustainability of the country's agriculture.
Water demand for domestic and industrial use is expected to increase by 72 and 210%, respectively by 2025. By contrast, the demand for water for agriculture will be dictated by the investments in water resources and irrigation development. With the declining contribution of the agricultural sector to the economy since the 1970s these investments are unlikely to be very high. Currently, water resources planning is focused on the development of the public and industrial water supply. A proposal for the development of a policy framework for water for agriculture is currently underway.
A water resources management policy for Trinidad and Tobago has recently been prepared and approved by the Board of Commissioners of the Water and Sewerage Authority for submission to the Ministry of Public Utilities. This document aims to specify the main objectives of water policy of the country and lays out specific guidelines, strategies and priorities for implementation.
A recent study (World Bank financed) on the water resources management strategy recommended the establishment of a new independent agency (Water Resource Management Agency, WRMA) attached to the Ministry of Planning, to which the present institutional functions of WRA would be assigned. Within the framework of the Inter-American Development Bank supported agricultural sector reform programme (1999), it has been proposed to disband the central Land and Water Development Division of MALMR and to replace it by the Division for Irrigation Planning and Management (DIPM). This new division would have the mandate of promoting, planning, administering and regulating the irrigation and drainage subsector. A national irrigation master plan to identify and prioritize areas for water management development and engineering studies for infrastructure development would be one of the first assignments of the new division.
It is also proposed that a new Water Resources Management Act be drafted and enacted, and that existing be amended accordingly.