Regional-based estimates of water use for commercial sugar-cane in South Africa

Abstract

The water use of rain-fed sugar-cane has come under the spotlight in South Africa, largely as a result of changes in legislation and a focus on streamflow reduction activities. In this study a robust relationship between sugar-cane yield and evapotranspiration
derived by Thompson in 1976 is applied in conjunction with regional cane production records in South Africa. These were used to provide regional estimates of water use of commercial rain-fed and irrigated sugar-cane as affected by environmental
limitations. The mean water use of sugar-cane at an industry scale was 598 mm·a-1. This included irrigated cane and is approximately 40% of the mean industry potential evapotranspiration for a full canopy crop. An estimate of water use of rain-fed cane is approximately 36% of potential evapotranspiration. The results shown in this paper provide strong evidence that simple comparisons of the potential evapotranspiration of different crops or land covers are of little value in determining potential hydrological impacts of land-use changes. This illustrates that the use of potential sugar-cane evapotranspiration to compare this crop\'s impacts on streamflow reduction to those of original vegetation is a problematic approach and is fundamentally
flawed.

Water SA Vol 32(1)pp:1-5