IMPROVED EFFICIENCY OF IRRIGATION WATER USE: A SOUTH AFRICAN FRAMEWORK

Irrigated agriculture plays a major role in the livelihoods of nations all over the world and in South Africa it is not different. With the agricultural water use sector being the largest of all water use sectors in South Africa, there have been increased expectations that the sector should increase efficiency and reduce consumption in order to increase the amount of water available for other uses. In a recent study on irrigation efficiency, the approach is that irrigation efficiency should be assessed by applying a water balance to a specific situation rather than by calculating various performance indicators such as conveyance efficiency or application efficiency. Unfortunately the concept of irrigation efficiency is frequently misunderstood leading to the widespread belief that water just disappears with low irrigation efficiencies and re-appears with improvements. The purpose of an irrigation system is to apply the desired amount of water, at the correct application rate and uniformly to the whole field, at the right time, with the least amount of non-beneficial water consumption (losses), and as economically as possible. The fraction of the water abstracted from the source that can be utilised by the plant, can be called the beneficial water use component and optimised irrigation water supply is therefore aimed at maximising this component. It implies that water must be delivered from the source to the field both efficiently (with the least volume for production along the supply system) and effectively (at the right time, in the right quantity and at the right quality). Optimising water use at farm level requires careful consideration of the implications of decisions made during both development (planning and design), and management (operation and maintenance), taking into account technical, economic and environmental issues. The South African framework covers four levels of water management infrastructure: -the water source, bulk conveyance system, the irrigation scheme and the irrigation farm. The water balance approach can be applied at any level, within defined boundaries, or across all levels to assess performance within the whole Water Management Area. Copyright (c) 2013 John Wiley & Sons, Ltd.