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Irrigation and drainage
Evolution of irrigation development
The long-term irrigation potential in Lesotho is estimated at 12 500 ha. In 1996, it was estimated at 2 520 ha for the foreseeable future. The distribution of this latter area over the districts is given in Table 4.
Other estimates of irrigation potential, considering only the available water resources and taking into account the reduced availability due to the LHWP, reckon that a minimum of 3 500 ha and up to 7 000 ha could be brought under irrigation if the Senqu River potential is fully exploited. However, others still, taking into account the high cost of irrigation development in the country, conclude that irrigation potential is limited by the market for high value crops and put the potential for new irrigation at about 1 000 ha.
In the last 40 years there have been many irrigation development projects in the country, almost all of them with funding form external donors. Public sector irrigation development has been largely unsuccessful due to a top-down and supply-driven approach on the part of government and donors and little consultation with, or participation by, farmers. Irrigation systems (mainly large sprinkler systems) have mostly been inappropriate for operation by smallholders as well as expensive to install and to run. As a result, farmer commitment and the overall sustainability of the irrigation works have been poor. Many irrigation schemes have been converted back into dryland farming.
The more successful irrigation projects in Lesotho, such as the small-scale irrigation and water harvesting projects, are based on an individual approach to communally owned irrigation schemes, where farmers control the on-field crop production activities. Private irrigation, consisting mainly of home gardens and small market gardens, is successful and is contributing to meeting household food security needs, as well as supplying rural markets.
The Ministry of Forestry and Land Reclamation (MFLR) investigated potentially irrigable catchments requiring water storage infrastructures for long-term development and identified 14 areas in the mountain districts of Mokhotlong, Thaba Tseka and Qacha’s Nek. Out of the 14 areas, six are already operational and MFLR has constructed stone water tanks on some of the sites. Collaboration with the Irrigation Section of the Ministry of Agriculture and Food Security (MAFS) should be forged to improve progress on these sites.
The Agricultural Sector Investment Programme (ASIP) intends to improve the viability and sustainability of existing public irrigation schemes by making them more responsive to demand, and, subject to demand, to expand irrigation for fruit and vegetable import substitution, employment creation and enhanced food security.
By 1999, of the 2 637 ha equipped for irrigation only 67 ha were still under operation, and this still relied heavily on government/donor support, although the latter has declined in recent years (Table 5). Of the total equipped area, 175 ha were small schemes (< 100 ha) and 2 462 ha were large schemes (> 100 ha) (Table 5 and Figure 2). In small schemes mostly vegetables are grown and surface and sprinkler systems are used. Large schemes were equipped for sprinkler irrigation, but as the schemes never managed to make a profit, they are no longer irrigated. The two types of irrigation systems commonly used are sprinkler and surface irrigation. Sprinkler irrigation is the most common, while surface irrigation is not so widely used because of the topography of Lesotho.
Depending on pressure, three categories of irrigation are distinguished:
- Pressure < 5 m; taps with buckets or surface irrigation;
- Pressure from 5 m to 20 m; low pressure system;
- Pressure > 25 m; high pressure system.
Pressures over 25 m are normally produced by engine- or motor-driven pumps using petroleum or electricity.
Role of irrigation in agricultural production, the economy and society
Vegetables are produced in fairly large quantities under irrigation but production remains very seasonal. The main crop is cabbage, but carrots, spinach and a variety of other crops are also grown. There are both large-scale farmers (often using rented land) and smaller farmers working under irrigation programmes.
Home gardens are an important source of horticultural produce in Lesotho, where an estimated 70 percent of rural households produce some vegetables. Most home gardens are rainfed, supplemented with irrigation from household and/or community municipal water supplies, although some families have invested in small pumps supplied by streams and ponds. The produce from home gardens is mainly for self-consumption, with limited quantities appearing on the local village market.
Vegetable cultivation in the Small-Scale Irrigation Vegetable Project gave a net income of US$2 300/ha in 1992. Yields achieved in various projects range from 1.9 to 3.6 t/ha for maize, between 3.5 and 13.5 t/ha for potatoes, and from 2 to 11.5 t/ha for onions.
Farmers in Lesotho may be categorized as shown in the Table 6.
Irrigation development in Lesotho is expensive and figures of up to 12 000 US$/ha are given for previous schemes. At present the cost of a system comprising gravity-fed, low-pressure sprinklers, excluding mainline pipe from tank/reservoir to the edge of the field and without installation, is estimated at about US$2 500 /ha. High-pressure systems are estimated to cost about US$7 900/ha, leading to the conclusion that the high-pressure system is expensive and will need high-level management to recover the costs.
The following costs for small-scale irrigation development are given:
- Treadle pump system: US$200-370 (for irrigated areas of 0.6 and 1.8 ha, with one pump);
- Drag-hose sprinkler system fed by a pump: US$1 500-2 300 /ha;
- Low-pressure gravity-fed sprinkler: US$1 950-2 750/ha.
The rates of return from irrigation schemes according to energy used to bring water from source to the field are shown in the Table 7.
From the previous table, studies concluded that probably only gravity-fed systems produce an adequate, commercial rate of return. Investments in pump-based irrigation in Lesotho should rather be considered primarily as social investment.