Read the full profile
Irrigation and drainage
Evolution of irrigation development
Around 13 000 ha have been identified as suitable for irrigation on the basis of soil and water availability in the Limpopo, Okavango and Chobe river basins. However, this figure is based on major surface water resources thus ignoring the potential for small-scale irrigation from minor surface water or groundwater resources.
Irrigation in Botswana is more or less synonymous with horticulture. Some irrigation of fodder (mostly alfalfa) occurs in very small areas but generally irrigation is used for the production of vegetables (mainly tomatoes, potatoes, cabbage and leafy vegetables, green mealies, onions, water melons, butternut squash and beetroot) and citrus crops (mainly oranges) (Figure 3).
The 1 381 ha developed for full/partial control irrigation in 1992 increased to 1 439 ha in 2002, but only about 620 ha was irrigated in the dry season in 2002 (Table 4, Table 5 and Figure 2). The rest of the surfaces were not irrigated owing to factors such as no water, poor marketing conditions or simply the cost of irrigating. No recent figures on irrigation technology are available, but in 1992, 15 percent of the equipped area was equipped for surface irrigation, 65 percent for sprinkler irrigation and 20 percent for localized irrigation (Figure 4).
Depending on the amount of flooding experienced, there are up to 6 500 ha of recession agriculture - molapo - in the Okavango and Chobe river basins, with the main areas being Chobe and Ngamiland West and East districts. Extensive low-lying areas regularly flood at two different times of the year:
- In the Chobe area this flooding begins with the start of the rainfall (runoff is constrained by flat topography and depressions with slightly heavier soils) in January-February and continues through to March-April when water is received from the Rivers Linyati (Kwando in Angola) and Chobe and also from the Zambezi (all with sources in Angola);
- In the Okavango area, further west, the flooding from the river starts in June-July. The Okavango has its source in Angola and rises in March-April but the floods are attenuated by the distance. These floods start to recede in October and then any residual moisture is supplemented by rainfall from November onwards.
Local subsistence farmers have developed a system of agriculture to utilize residual moisture according to the time of year. At the end of the flood season, areas are ploughed (using animal power) and may be bunded if further floods are possible. Bunds are usually used for protecting planted areas and not for water control. The flooding varies considerably from year to year and the farmers have developed a system to cope with these changes. Crops are planted on the ploughed areas and also on the margins of the receding flood and at other times on the banks or beds of the streams and rivers.
The main crop grown is maize for green mealies, sold in the markets of Maun and Kasane as early as December, and for grain. Other crops include water melons and pumpkins as well as vegetables, beans and similar short-season cash and food supplement crops. Cash crops tend to be grown more in locations close to the main towns of Kasane and Maun.
Role of irrigation in agricultural production, the economy and society
The Ministry of Agriculture calculates in-field costs, excluding pumping and delivery costs to the farm/scheme boundary, as follows:
- Micro-jet (6 m x 6 m spacing for citrus or similar tree crops) : US$1 040/ha,
- Drip irrigation (0.9 m lateral spacing for row crops): US$6 455/ha,
- Drip irrigation (3.0 m lateral spacing for trees): US$2 180/ha,
- Sprinkler irrigation (3 laterals per ha - hand move): US$2 745/ha,
- Centre-pivot (13-ha machine): US$30 910/unit.
The recent Contract Award Wastewater Reuse Project to develop 203 ha (about 180 ha net) in Gaborone at Glen Valley has a contract cost of over US$1.8 million which, with in-field works, is likely to have a development cost of over US$13 000/ha: about US$10 000/ha for land clearance, the main pumping station, provision of potable water and sewerage piping and drainage works and about US$3 000/ha for the in-field sprinkler works.