Simulation of efficiency impact of drainage water re-use: case of small-scale vegetable growers in North West Province, South Africa

This paper focuses on estimating the effect of drainage water reuse on the technical efficiency of small-scale vegetable growers in South Africa applying a data envelopment analysis (DEA). In the semi-arid North West Province of South Africa water scarcity and the soon to be implemented water charges have urged farmers in small-scale irrigation schemes to evaluate the efficiency of their water use. Data on 60 farmers were used to estimate the level of technical efficiency and the effect that drainage water re-use could have on efficiency levels. This effect of water reuse was simulated by a 5, 10, 15 and 20 per cent reduction in water use at farm level. A Malmquist productivity index was calculated to evaluate the effect of these reductions. The main finding was that under current farming conditions many farmers operated at suboptimal levels of technical efficiency. While a reduction in water use evidently increased factor productivity for most farms, the effect clearly varied strongly between farms. This confirms the need to take a systems approach for this type of evaluations