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Irrigation and drainage
Evolution of irrigation development
The main irrigation and drainage works and schemes were executed in the early to mid twentieth century, with a peak of construction and rehabilitation in the 1950s and 1960s. In the last decades, the area under irrigation has decreased due to the poor and deteriorating state of canals, drains, sluices, pumps and other necessary structures. At present, many irrigation areas are in need of rehabilitation. Total area equipped for irrigation in 2012 is estimated at 143 000 ha (Table 5).
The vast majority of agricultural activities takes place in the coastal plains. For more than 8 km inland the land is below sea level at high tide. Therefore, drainage and water control are major problems, and agricultural development has always been tied to the defence against water intrusion from the sea and from rainwater runoff.
Irrigated areas are concentrated between the mouth of the Pomeroon river and the Corentyne river. They are located in five out of the country’s ten administrative divisions. All areas with fully developed drainage and irrigation facilities are classified as Declared Drainage and Irrigation Areas (DDIA). In addition, the sugar estates also have irrigation and drainage infrastructure.
In the DDIA in Regions II, III, IV and V irrigation is done by surface flow, via gravity from high level storage in the conservancies. The areas in Region VI are supplied from pumps that extract from the Canje river basin, supplemented by the Berbice river basin, thus irrigation in this Region VI is mostly powered by pumping. Very few control structures exist along the main canals and distributor canals. Flows in the secondary canals are controlled by headgates, and farmers derive water from secondary canals normally by gravity. Minor drains are interspersed with secondary canals that drain directly to the sea through sluice gates (some are associated with pumping stations) or to a façade drain, which drains to the sea at regular intervals. Sluice gates are open twice a day at low tides. Irrigation canals within sugar estates have no slope and are often used for cane transportation. Surface irrigation is the only technology used in the irrigation schemes.
Most irrigation infrastructure needs extensive rehabilitation, with the exception of some sugar estates and some infrastructure that is being maintained by large-scale farmers. The systems’ state of disrepair contributes significantly to lowering Guyana’s water use efficiency. Another important cause of poor water use efficiency is inadequate water management, a result of conflicting needs of farmers who have different crop calendars. While there are no recent studies measuring water use efficiency, efficiency levels are unlikely to exceed 40 percent.
At the end of the 1990s, the total length of the irrigation canals in Guyana was 485 km of main canals and 1 100 km of the secondary canals.
All the drainage and irrigation systems are open surface channels. However during dry spells, when the water supply level falls below the field intake, pumps are used to meet irrigation requirements. Channels are often used as refuse disposal sites in some areas especially adjacent to populated villages/towns, in addition to aquatic growth and siltation due to runoff over cleared and ploughed areas to facilitate cultivation. Hence, there is a need for regular maintenance of these drainage and irrigation systems.
In the east in Region VI, the irrigation requirements are met by extracting water from the Canje river, at six locations along a section of the river which then is directed northwards to the coast where irrigation is needed. Above the points of extraction is also a canal linking the Berbice river to the Canje river, called the Torani, which supplements the flow of the Canje river to facilitate extraction and limit the intrusion of salt/brackish water into the areas upstream where the pumps are located. The areas supplied by these systems are Declared Drainage and Irrigation Areas (DDIA) while those areas that are not served by these are designated Undeclared Drainage and Irrigation Areas (UDIA).
Role of irrigation in agricultural production, economy and society
Crop production (except sugarcane) and livestock production are characterized by the predominance of small farms. According to the farm household survey in the 1990s, farms of less than 6 ha accounted for about 75 percent of the country’s 24 000 farms. It is estimated that about 70-80 percent of these small farms are geared to rice production. Many of these small farms combine their crop production with some milk production. There are, however, several larger agricultural operations that include private rice growers, some medium- and large-size forest and fishing operations, and large public-sector enterprises.
In the 1980s, sugar and rice were the primary agricultural products, as they had been since the nineteenth century. Sugar was produced primarily for export whereas most rice was consumed domestically. Other crops included bananas, coconuts, coffee, cocoa and citrus fruits. Small amounts of vegetables and tobacco were also produced. During the late 1980s, some farmers succeeded in diversifying into specialty products such as heart-of-palm and asparagus for export to Europe. The extent of Guyana’s economic decline in the 1980s was clearly reflected in the performance of the sugar sector. Production levels were almost halved, from 324 000 tons in 1978 to 168 000 tons in 1988. Sugar production for 1994 was 252 615 tons and was the major export commodity, contributing 28 percent to total exports. The rice industry has been leading growth (1993-96) with production and export earnings rising steadily. In 1995, rice production reached 350 000 tons.
In 2010, total harvested irrigated cropped area was estimated at 179 000 ha, meaning an irrigated cropping intensity of 140 percent. Rice accounts for 131 000 ha or 73 percent of the harvested irrigated copped area. Irrigation allows double cropping of rice, which provides reasonable returns on investment, the average yield for rice being between 4-6 tons/ha. Sugarcane represents 41 600 ha (23 percent), vegetables 4 000 ha (2 percent) and citrus 2 000 ha (1 percent) (Table 5 and Figure 2).
Irrigation development costs are US$3 647/ha composed as follows: construction of head work US$2 187/ha, conveyance system US$860/ha, field system US$600/ha. Maintenance costs are US$33/ha per year.
Women and irrigation
Women in Guyana have always been involved in agriculture at both formal and informal levels of production, processing and marketing. However, their involvement has been underestimated in statistics. Women in rural areas have less access than men to resources, particularly to productive assets such as land and water. Access to water and irrigation depends not only on the availability of water, but also on the legal and regulatory systems governing its distribution and use. In most cases, access to water is contingent on land tenure; as a result, women may find themselves disadvantaged. Rural women spend an average of 8.4 hours weekly fetching water for both domestic and farm use. Some problems that women face in agriculture are the lack of training, lack of farming equipment and poor drainage and irrigation (Rutherford and Odie-Ali, 1996 and IADB).
Status and evolution of drainage systems
Drainage throughout most of Guyana is poor and river flow sluggish because the average gradient of the main rivers is only 0.02 percent. Drainage by gravity is possible only when the tide is low, and this form of drainage is affected by the ever-changing levels of the foreshore outside the sea defences. Therefore it has been necessary in many areas to resort to the expensive method of drainage by pumps. Land requires extensive drainage networks before it is suitable for agricultural use. In the 1990s, drainage canals occupy nearly one-eighth of the area of the average sugarcane field. Similarly, the main drainage infrastructure is about 500 km in length while the length of the secondary drainage system is 1 500 km. In 1991, the entire area equipped for irrigation, 150 100 ha, was drained.
The drainage systems were designed to facilitate the drainage of 37 mm of rainfall per day, through gravity at the low and falling tides. The recent record of rainfall events indicated that a higher drainage capacity is needed: approximately 50 mm/day is required for sugarcane (AGROTECH SpA/European Union, 2003).