Geography, climate and population
Jamaica is located to the south of Cuba and forms part of the Greater Antilles, at latitude 18o 15' N, longitude 77 o 30'W. The largest island of the English-speaking Caribbean, it boasts a total land area of 10 990 km2. In 1997 about 274 000 ha were under cultivation, 174 000 ha of arable land and 100 000 ha of permanent crops. The country is divided into fourteen (14) administrative districts, called Parishes.
There are a series of mountain ranges along the major WNW-ESE axis of the island. In the eastern third, these mountains generally exceed elevations of 1 000 m with Blue Mountain Peak, the highest point rising to a height of 2 256 m. Major alluvial lowlands occur in the southern half of the Island, where they are often associated with coastal swamps. The other main topographical feature is a narrow, discontinuous coastal plain where 65% of the total population reside.
The island's climate can be classified as tropical maritime, hot and humid with a temperate interior. Mean daily temperatures range from a seasonal low of 26 ° C in February to a high of 28 ° C in August. Daily sunshine hours are fairly constant throughout the year, averaging about 8.2 hours in the southern plains.
Long-term mean annual rainfall over the island is about 1 980 mm. Much of the rainfall results from the northeasterly trade winds, which deposit most of their moisture on the northern slopes of the axial mountain ranges and the southern half of the island is in rain shadow. Annual rainfall on the northeastern slopes of the Blue Mountain Range is generally 3 000 to 5 000 mm, whereas in the south coastal plains of St. Catherine and Clarendon it is generally less than 1 500 mm. Annual rainfall exhibits a characteristic pattern, with a primary maximum in October and another in May. The main dry season lasts from December to April.
Jamaica regularly comes under the influence of tropical storms and hurricanes during the period of July to November, characterized by flood-producing rainfall of high intensity and magnitude.
Jamaica's population was 2 515 000 inhabitants in 1997, of which almost 46% was rural. The average density is estimated at 229 inhab./km², but is unevenly distributed. Over one million people (about 43% of the total) live in Kingston, Saint Andrews and Saint Catherine, the main urban centres, while Trelawny Parish has the lowest density with 83 inhab./km2. In 1996, approximate 65% of the total population lived within 5 km of the coast. The average annual population growth rate in the 1990-1997 period has been estimated at 0.85%. Agriculture contributes approximately 8% to the GDP and accounts for 12% of export earnings from sugar, banana, coffee, cocoa, spices and vegetables. In 1997, the sector employed some 22% of the labour force.
Traditionally Jamaica has had a very strong agricultural base, although since 1950 there has been a gradual shift from a dependence on sugar cane and bananas to the bauxite/alumina, manufacturing and tourism sectors. The latter three are currently the main foreign exchange earners. The large farms are generally located on the plains while small farmers occupy the hillsides.
Renewable water resources
Fifty-six percent of the average annual rainfall are lost to evapotranspiration. The internal renewable water resources (IRWR) are 9.4 km3/year, with 5.5 and 3.9 km3/year for surface and groundwater respectively (see following table).
Approximately 44% of these IRWR are considered exploitable or reliable, defined as daily water flow exceeded during 90% of the time for surface water and quantity of water which can be withdrawn over a long period without impairing the aquifer as a water source or causing contamination by seawater intrusion for groundwater. Of the total reliable yield of 4.09 km3/year, 80% are contributed from the limestone aquifer, 4% from the alluvial aquifer and 16% from surface water runoff. About 20% from the limestone aquifer are developed through wells, mainly in the Río Cobre and Rio Minho. However, in other basins, the water is generally available as base flow and is exploitable through run-of-river developments.
Major water basins of Jamaica
1. Total area is slightly different from country area, as they come from different sources of information.
Lakes and dams
There are two major raw water storage facilities, both located in St. Andrew. The Mona Reservoir, with intakes at the Hope and Yallahs Rivers, has a storage capacity of 3.67 million m3. Hermitage Reservoir with intakes at Ginger River and Wag/Morsham River, has a storage capacity 1.78 million m3.
Annual water withdrawal in 1993 was estimated in 928 million m3 and the agricultural sector was the major user of water (75%). The other major water users were domestic water supply 17%, industry 7% and tourism 1%. About 92% of the water was withdrawn from groundwater sources and the remainder from surface water.
Figure 1: Water withdrawal by sectors. Total withdrawal: 928 106 m3 in 1993.
Only 11% of the surface water and 25% of groundwater of the exploitable water resources are currently utilised. The National Water Commission (NWC) provides water to various supply systems from wells, rivers and springs. A total of 500 water supply facilities are operated by the NWC to supply 78% of total demand.
Access to water supply in 1998 was available to 75 % of the rural population and to 95% of those residing in urban areas. Access to water supply via house connections was available to approximately 65% of the population. The remaining 35% of the population were supplied through a variety of means: standpipe, rainwater collection systems, water trucks, wayside tanks, community catchment tanks.
The NWC operates sewerage facilities which serve about 15% of the population. Centralized systems are located in Kingston and St. Andrew, southeast St. Catherine and Montego Bay in St. James. The NWC is also responsible for a number of small sewerage systems, utilizing package plants, which are associated with housing developments in various locations throughout the country. Treatment is given to secondary level for 50% of waters. For the remainder of the population, sewage disposal is accomplished via septic tanks, soak-away pits, tile fields and pit latrines.
There is concern that over-exploitation, sewage effluents and industrial wastes are affecting aquifers and surface waters at an alarming rate. As much as 10% of the groundwater resource has been either abandoned or use is restricted due to saline intrusion or pollution. Wastewater reuse is included in the National Irrigation Development Plan (NIDP), as an expensive source of irrigation water which nonetheless should be investigated as a pilot research project. Fifty percent of the unused water resources in the Liguanea Basin serving the Kingston and St. Andrew area are contaminated with nitrates.
Irrigation and drainage
According to the NIDP, areas suitable for irrigation have been classified into three land categories: (I) lands which may be irrigated with all common techniques of irrigation; (II) lands suited only to sprinkler and micro-irrigation techniques; and (III), lands with generally steep slopes (>10%) and thin soils, which are productive with careful management of the limitations and responsive to manual irrigation. This third category applies mainly to small hillside farmers. From this analysis 90 811 ha were classified as Category I and II, while 97 095 ha or 9% of the island were classified as Category III. These categories do not take water resources into account.
Irrigation has always played a significant role in the island's agriculture, and the need to continuously improve irrigation practices has long been recognized. Over the years some of the improvements which have been made have included channel lining and utilization of closed pipes in order to improve conveyance efficiencies, the use of water measuring techniques to encourage improved management, and the use of overnight storage facilities. Approximately 9% (about 25 000 ha) of the area under cultivation are currently irrigated, and about 9 000 ha require rehabilitation.
Half of the total area irrigated comprises public schemes which are managed by the National Irrigation Commission (NIC), while the other half is on individual private systems and on commercial estates, where banana, papaya and sugar cane are the major crops grown. Three-quarters of the area are under surface irrigation, 17% are equipped with sprinklers and 8% with micro-irrigation systems (Figure 2).
Figure 2. Irrigation area (ha)and techniques in the public and private sectors (1997). Total area under irrigation: 25575 ha.
The NIC has responsibility for operating and maintaining delivery systems for six public districts: Rio Cobre, St. Dorothy, Mid-Clarendon, Hounslow, Braco and Yallahs. The networks consist of open canals and pressurised pipelines. Water is abstracted from surface diversions, small storage reservoirs and deep wells. In the private sector, in addition to sugar estates in St. Catherine, which receive much of their irrigation water from NIC, there are several commercial estates, which have implemented their own irrigation systems. Many farmers with small holdings in most parishes, irrigate vegetables or fruit trees using their domestic water supply or from local surface sources or springs or stored precipitation. NWC has estimated that in areas like Essex Valley or St. Elisabeth, more than 60% of domestic water is used for irrigation.
Figure 3: Irrigated area by crops (1997)
While a wide range of crops is irrigated, 76% of all irrigated lands are under sugar cane production, followed by bananas (8%), pasture (6%), and vegetables (4%). The remaining 6% comprise papaya, orchards, coffee and other crops (see Figure 3).
Water management, policies and legislation related to water use in agriculture
Potable water supplies are the responsibility of the National Water Commission (NWC), the major supplier, the Urban Development Corporation and the Parish Councils. The NWC's responsibilities include the provision of potable water supply services and the collection, treatment and disposal of wastewater.
The NIC is responsible for the management, operation and maintenance of all the public irrigation systems in Jamaica. Activities include the harnessing and distribution of groundwater and surface water for allocation to farmers and also non-agricultural users. The NIC's primary mission is to maximize effective use of irrigation through improved conveyance and distribution, and to provide guidance and training in on-farm water management techniques in an effort to increase productivity and profitability in the agricultural sector and so achieve and maintain self-sustainability of the irrigation industry.
The Water Resources Authority (WRA) was established by statute to regulate the island's water resources. The WRA has responsibility for management, protection and controlled allocation and use of Jamaica's water resources. This is achieved through the development and administration of a long-term comprehensive "Water Resources Development Master Plan for Jamaica", necessary to enable rational decision making on current and future water use and allocation which provides economic and environmentally sound development options. The WRA was established by the Water Resources Act of 1995 enacted in April 1996. This Act repealed the Underground Water Control Act and the Water Act. The WRA replaces Jamaica's previous hydrological agency, the Underground Water Authority.
The responsibility for formulating and implementing the Government's policy on environmental management is vested in the Natural Resources Conservation Authority. Its responsibilities include: watershed protection and management, environmental monitoring and enforcement, promoting industry compliance for the consistent meeting of effluent and waste standards by companies, development of a system of national parks and protected areas, coastal zones management, environmental education, increasing public awareness of environmental issues and promoting the use of environmental impact assessments.
Prospects for agricultural water management
There are plans in place to continue expanding water supply to communities, through rehabilitation of the existing system (the level of unaccounted-for-water is currently at 63%) and expansion of capital infrastructure.
With respect to irrigated agriculture, the National Irrigation Development Plan (1998) proposes a total of 51 irrigation projects for implementation over a seventeen-year period. This plan is aimed at increasing agricultural production to benefit individual farm families and the economy as a whole. Some of the possibilities for developing additional water for irrigation include the export of surplus water from one basin to another, construction, where feasible, of additional storage reservoirs and micro dams; implementation of a groundwater recharge programme and a review of the irrigation policy.
Some of the issues to be examined with respect to irrigation policy include:
Main sources of information
Statistical Institute of Jamaica. 1997. Statistical Abstract 1996.
Underground Water Authority (Water Resources Agency of Jamaica). 1990. Water Resources Development Master Plan. Final Report. Main Volume. Government of Jamaica. Kingston.
Natural Resources Conservation Authority. 1998. State of the Environment. The 1997 Report. Government of Jamaica. Kingston.
National Irrigation Commission Limited, Planning Institute of Jamaica and Inter-American Development Bank. 1998. Preparation of a National Irrigation Development Plan and Preparation of an Irrigation Investment Project. Executive summary. Government of Jamaica. Kingston.
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