South Africa is classified as a semi-arid country with 465mm of average annual rainfall. This is below the global average estimated at 860mm per annum. Roughly 20% of South Africa receives less than 200mm and 47% receives less than 400mm yearly.
The figure below indicates the rainfall distribution.
Figure 1: South Africa’s Mean Annual Precipitation (MAP) (Source: Schulze 2011)
Water use for irrigation agriculture takes place on an estimated 1.1% of South Africa’s total land surface area, often in low rainfall areas where supplementary irrigation needs are very high or total irrigation is practiced. A relatively inefficient mode of irrigation was found to be in use in most cases.
In 2000 eleven of the 19 catchments listed in the table below indicated a negative water balance. In South Africa’s major catchments local water demands exceed the reliable local yields.
Table 1: Reconciliation of water availability and requirements for 2000 (million m3/annum) (Source: DWAF 2000) (* refers to the amount that can be reliably provided 98 years out of 100, with ecological reserve requirements already subtracted)
The figure below indicated South Africa’s water usage by sector. Irrigation comprises nearly 60% of total water consumption. Irrigation water usage in agriculture was 6907 million m³ in 2002. This was 87% of the total water allocation for irrigation purposes (7920 million m³) as reported by the Department of Water Affairs and Forestry.
Figure 2: SA water use by sector. (Data Source: DWAF 2000)