|Pays, régions, bassins fluviaux|
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|Irrigation et drainage|
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|ODD Cible 6.4|
|Year: 2005||Revision date: --||Revision type: --|
|Regional report:||Water Report 29, 2005|
The Gambia is situated in the Sahelian zone on the West Coast of Africa. It is the smallest country on the African continent with a total area of 11 300 km2, of which about 20 percent is considered as wetland. The River Gambia runs from east to west, dividing the country in two strips of land 25 to 50 km wide and about 300 km long.
In the Gambian landscape two major geomorphological units may be distinguished, the uplands and the lowlands:
The vegetation of the Gambia is of the Savannah type with shrub and grass understoreys. Mangroves are found in the western half of the country in the floodplains of the River Gambia. The cultivable land area is estimated at about 430 000 ha, which is 38 percent of the total area. In 2002, arable land was 250 000 ha, while 5 000 ha were under permanent crops (Table 1).
The Gambia lies in the Sahelian agro-climatic zone and its climate is characterized by two different seasons: a rainy season from June/July to October and a long dry period between November and May. The dry season is characterized by a hot, dry wind blowing southwards from the Sahara desert, which can bring sandstorms. There has been a steady decline in rainfall from 1875 onwards which is causing increased salinity in the lowlands and increased aridity in the uplands. Average annual rainfall is 836 mm, with a spatial variation from over 1 000 mm in the south to less than 800 mm in the north. In the areas where there is less rainfall, it is generally more reliable. As much of the wet season rainfall falls in short heavy storms, water conservation is essential to ensure crop security. However, there is a risk of washout due to the severity of the rainfall. The average daily temperature is 30 °C in the dry season and 27 °C in the wet season.
Total population was almost 1.5 million in 2004, of which 74 percent was rural. Annual population growth rate was 2.7 percent, and population density reached 129 inhabitants/km2. In 2002, 82 percent of the population had access to improved drinking water sources; this coverage was 95 percent and 77 percent for urban and rural areas respectively. Sanitation coverage was 53 percent for the whole country in 2002, corresponding to 72 percent in urban and 46 percent in rural areas.
The Gambia is among the poorest countries in the World. It was ranked 155th out of 177 in the UNDP Human Development Index of 2002. Poverty in the Gambia has increased drastically since the early 1990s. It is a predominantly rural phenomenon, although urban poverty is sharply on the rise. Women are more vulnerable to income poverty and as regards access to property. Regional variations are clearly visible, showing a high prevalence rate in the eastern half of the country.
The GDP of the Gambia was about US$386 million in 2003. Agriculture accounted for 27.8 percent of GDP, and 78 percent of the total economically active population was employed in the sector. Agriculture accounts for about 90 percent of export earnings, and peanuts and peanut products make up about 70 percent of exports. Foodstuffs, especially rice, constitute the most important imports.
The Gambia’s preferred staple food is rice, which is traditionally cultivated primarily in the lowlands as a subsistence crop. Most farmers are too poor to buy the required fertilizer and agricultural machinery, and the small areas of cultivation and primitive farming technology keep output low, about 1.5 tonnes/ha. Of the total available food, only about half is produced in the country and the remaining 50 percent is made up of commercial imports and food aid. The food import bill was estimated to be US$40 million for the year 2002. However, there is a food shortage that affects about 54 percent of the rural and 33 percent of the urban population, especially during the rainy season when the calorie requirement is highest because of the intensive field work.
Agricultural farming in the Gambia is characterized by subsistence rainfed production, depending on the distribution and amount of rainfall. Farmland can be classified into upland and lowland:
The following main rice ecologies can be identified in the country:
The River Gambia originates in Fouta Djallon in the mountain region of Western Guinea and flows through Senegal before entering the Gambia. Within the country, the River Gambia flows from east to west for about 400 km. It is a major waterway and tourist attraction. Its floodplains, riverbanks and wetlands are important habitats for wildlife and play an important role in local livelihood strategies. Its flow is highly seasonal. The maximum flow occurs at the end of the rainy season in late September or October with a flow of about 1 500 m3/s; the minimum dry season flow is less than 4.5 m3/s. Both measurements are taken at Gouloumbo in Senegal. Because of the flat topography there is a pronounced marine influence and the river’s seasonality and salinity have important repercussions on land use.
The country’s total actual renewable water resources are estimated at 8 km3/year, of which about 3 km3 are internally produced and the remaining 5 km3 represent the inflow of the River Gambia from Senegal (Table 2). It is estimated that internally produced groundwater amounts to about 0.5 km3/year, all of which is drained by the River Gambia and becomes the base flow of the river. Groundwater is available in all parts of the Gambia. The country is located in one of Africa’s major sedimentary basins and is often referred to as the Mauritania/Senegal Basin. It is characterized by two main aquifer systems with water table depths varying from 10 m to 450 m.
Along the river, the width of the valley varies from 20 to 40 km and three major sections may be distinguished:
The Gambia is located entirely within the Gambia River Basin, which is shared between Senegal (77.5 percent of the basin area), the Gambia (13 percent), Guinea (9 percent) and Guinea-Bissau (0.5 percent). The Gambia signed several international agreements and conventions regarding the Gambia River Basin, namely:
Total water withdrawal was 31.8 million m3 in 2000. The largest water user was agriculture with 21.3 million m3/year (67 percent), followed by the municipal sector with 6.9 million m3/year (22 percent) and industry with 3.6 million m3/year (11 percent) (Table 3 and Figure 1).
Surface water is rarely used as a source of potable water in the Gambia, because of the continuously saline conditions which exist in the lower reaches of the River Gambia and its tributaries, where the population centers and tourism facilities are located. The potable water demand for urban areas, tourism, industry, irrigation and livestock watering is supplied by groundwater sources.
Irrigation potential in the Gambia was estimated in 1984 to be 80 000 ha. There are several irrigation development projects under way in the country:
Accurate up-to-date figures on irrigated areas are not available. In 1991, the area equipped for full or partial control irrigation was estimated to be 1 670 ha; this figure might have increased to 2 149 ha by the year 1999, referring to the sum of the JPSP, RIDEP, SSWC, and Lamin-Bakau schemes. In addition, non-equipped wetlands and inland valley bottoms are cultivated and these accounted for approximately 13 170 ha in 1991. These areas represent mangrove swamps and freshwater swamps, where rice is grown from August to January by constructing simple protection dykes. Thus, the total water-managed area is estimated at 15 319 ha or 7 percent of the cultivated area (Table 4 and Figure 2). All the area equipped for full or partial control irrigation is surface-irrigated, either with pumped schemes (818 ha or about 38 percent of the area in 1999) or by employing tidal irrigation (1 331 ha or about 62 percent of the area).
In the low-lying marshy areas tidal flows are employed for irrigation purposes. This is feasible in the middle reaches of the river, beyond the 240 km mark, where river water is not salty. Tidal irrigation is very different from ordinary gravity irrigation or pump irrigation, as it takes advantage of the ocean tides to force river water onto the fields. Tide heights vary from 3.5 m at the mouth of the River Gambia to 0.9 m at Basang, 310 km upstream, and as a general rule tidal irrigation can be used to water marshy fields with an elevation of less than 1.7 m above the average sea level. A water control valve is usually installed where water enters the system, and the system should have separate inlets and outlets. River water is allowed to flow into the system at flood tide, and the outlet valve is shut as the tide ebbs to keep the water on the fields. Areas where tidal irrigation is feasible include Wassu, Kuntaur, Tobakuta, Sukuta and Bauajali on the north bank, and Sapu, Willirgara, Kuffzally and Yidda on the south bank in the Middle River Division.
To avoid an increase in salinity, the safe limit for irrigation from the River Gambia, without major dam construction, was estimated to be a maximum of 2 400 ha in the dry season. The lower and lower central river sections (up to Carrol’s Wharf) contain considerable areas of actual and potentially acid sulphate soils.
The main irrigated crop is rice. In the Jahaly Pacharr Smallholder Project (JPSP), a high rice yield is achieved in the areas receiving pumped water. Between 4 and 7 tonnes/ha is expected rather than the 3-4 tonnes/ha achieved in the tidal areas.
Estimates on the cost of installing irrigation systems vary from US$4 000/ha for tidal irrigation to US$10 000/ha for pump irrigation. Analyses taking into account installation and production costs, the anticipated rice output after implementation, the value of that output, etc., indicate that the profit/cost ratio for tidal irrigation is 2.02, while that for pump irrigation is 0.72. It is evident, therefore, that by using tidal irrigation the Gambia could increase its rice output significantly. Costs for certain water control structures are: about US$3 per metre of dyke in the valleys, including labour and all other inputs; about US$30 per metre of concrete spillway; about US$1 per metre of contour or diversion bund, including the rock dams that are installed in the system at road crossings for example.
In the Gambia, the resources that are made available for irrigation, especially labour, are influenced by a particularly complex network of rights and obligations in rural society. Women in rural communities play an important role in the allocation of family labour to food production tasks. Despite this role, women are often stressed because old traditional obligations are upheld in new situations. The introduction of irrigation, or the technical formalization of existing water-use systems, involves in most communities a change in the traditional farming system. Women are major participants in irrigation at field level, however there is only scant evidence that they participate significantly in water management or policy decisions at the system, regional or national levels.
The Colonial Development Corporation (CDC) implemented irrigation and development schemes but started the alienation of women’s land rights by assuming that men own the land. This approach ignored the fact that women had significant access to land resources and their benefits from rice farming as well as responsibilities for food and support of children. Post-colonial development schemes made similar mistakes. Irrigated rice projects funded by the World Bank, China, IFAD, etc., be they small- or large-scale double-cropping schemes, ignored the elaborate system of land rights and cropping responsibilities. The women’s land was taken and they were expected to labour on men’s fields. Thus women had no means of generating the same income and maintaining independent decision-making rights over their labour and livelihoods. As a result of this situation, women tend to rebel and refuse to work at certain times of year when they want to work on their own fields, and they form work groups to drive up wage labour. As a consequence, many projects are expensive and unsuccessful.
In the course of the Jahaly Pacharr Smallholder Project (JPSP), the patterns of access to land and distribution of benefits have undergone a number of changes. However, the registration of project land in women’s names has had only a limited impact on the power bases of men and women. In the Rice Irrigation Development Project (RIDEP), training for the operation and maintenance of power tillers is offered to both men and women. However, while the women were enthusiastic, the older men of the village clearly disapproved of women handling power tillers and commented that they did not want women coming home too tired to do other duties.
Gender issues in irrigation in the Gambia can be summarized as follows:
In tidal irrigation schemes, drainage is the paramount concern during the rainy season; during the dry season, irrigation is the most important consideration. The ditches of a tidal irrigation system must therefore have a dual irrigation/drainage function. It is necessary to prevent irrigation water from flooding the fields, and attention must be paid to controlling irrigation and drainage at the times of flood and ebb tides.
Policy guidance and technical support for agriculture are provided by the Ministry of Agriculture (MOA) through a Central Management Unit and four main departments. The Department of Agricultural Services (DAS) is responsible for Agricultural Extension Services, the Soil and Water Management Unit (SWMU), the Crop Protection Service, the Food and Nutrition Unit, and the Agricultural Communications Unit. The SWMU is in charge of developing policies for soil and water management, land capability zoning, upland conservation and development of small-scale water control schemes in lowland rice ecologies. It is divided into five sections, one of which - the Engineering Section - is involved in irrigation development.
The Department of Water Resources (DWR) of the Ministry of Natural Resources and Environment (MNR&E) liaises closely with the SWMU.
Most farmers involved in irrigation/water management belong to Water User Groups. In the IFAD-led Small-Scale Water Control Project SSWCP, a three-tier organizational structure was established:
However, none of these groups was working properly by the end of IFAD support in 1996 and both project staff and beneficiaries were unclear about responsibilities and work modalities.
Pumping irrigation water from the River Gambia has a potentially negative impact on the salt front in the river and thus on the environment overall. It has been estimated that if 1 m3/s is pumped from the Upper River during the dry season, the salt front can move up to 4 km upstream.
Deforestation is a problem due to the high and ever-increasing demand for fuel wood.
Given the low farmgate price of rice, the Government is considering alternative crops such as sugar cane, bananas and onions to justify investment in the rehabilitation of existing pump irrigation schemes.
By fully developing tidal irrigation and using superior seed rice together with the best cultivation technology, the Gambia can greatly increase output per unit area and even attain self-sufficiency. However, if tidal irrigation is to succeed in increasing the Gambia’s rice output, the following measures are required:
National policies give high priority to increased rice production using technologies which are environmentally sound and sustainable without subsidies. The Government also gives high priority to food security and poverty alleviation within the context of sustainable development.
Central Statistics Department, Ministry of Finance and Economic Affairs. 1993. Statistical abstract of the Gambia 1992.
Chancellor, F. 1996. Women in Irrigation: Case studies of schemes in the Gambia, Kenya and South Africa. HR Wallingford, UK. Report no OD/TN 82.
Department of Planning, Ministry of Agriculture. 1991. Statistical yearbook of Gambian agriculture 1990.
Department of State for Finance and Economic Affairs. 2002. Strategy for Poverty Alleviation (SPA II). Strategy for Poverty Alleviation Coordinating Office. The Republic of the Gambia.
FAO. 1982. The Gambia: Water resources development in the framework of the National Food Plan. Report prepared by P. Pallas and S. N’Guiamba for FAO project TCP/GAM/0104. Rome.
FAO. 1984. Agricultural Research in the Gambia River Basin. Rome.
FAO. 1994. The Gambia: Lowlands Agricultural Development Programme. FAO Investment Centre/IFAD Cooperation Programme report Nº 52/94 IFAD-GAM 15. Rome.
FAO. 1997. Treaties concerning the non-navigational uses of international watercourses: Africa. FAO Legislative Study 61. Rome, Italy.
FAO. 2001. The Gambia: Lowlands Agricultural Development Programme. Socio-economic and production systems study. Project document.
FAO. 2002. Water Control Component of the Special Programme for Food Security. TCP/GAM/2801 (D). Project Document.
International Cooperation and Development Fund (ICDF). 1999. Tidal Irrigation in the Gambia. In: ICDF. 1999 ICDF Annual Report - Special Report. 67-70.
Njie, M., and Mikkola, H. 2002. Management and development of the Gambia River fisheries: A case for the co-management of inland fisheries resources. In: Geheb, K., and Sarah, M.T. (eds.). Africa’s inland fisheries: the management challenge. Fountain Publishers. Kampala. 228ff.
Sonko, E.O. 2001. Gambian experience in water harvesting. In: FAO. Water harvesting in western and central Africa. Proceedings of a regional workshop held in Niamey, October 1999. Accra, Ghana. 103-108.
UNEP. 1998. Tidal Irrigation, the Gambia. In: UNEP. Sourcebook of Alternative Technologies for Freshwater Augmentation in Africa. Technical Publication 8a.
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