Methods, tools and institutional arrangements for water conservation and demand management in irrigated sugarcane

Abstract In this paper, methods, tools and institutional arrangements to facilitate water conservation and demand management (WCDM) in irrigated agriculture are discussed. Case study evaluations of the performance of irrigation system hardware and associated water management systems have shown that there is potential to reduce irrigation water applied by up to 20 percent per annum and to improve sugarcane yields, provided better design, management and maintenance procedures are implemented. Availability of appropriate guidelines and tools to effect water savings is, however, only part of the solution. Institutional arrangements for water allocation and management which provide positive incentives for the adoption of these tools and guidelines are needed. Traditionally, water has often been allocated in terms of a volume per unit time, issued at some estimated level of assurance. Such allocations are then managed using priority-based reservoir and river operating rules. This approach is shown to have significant disadvantages in terms of: ease of management, equitability, and potential to foment conflicts. Critically, it also provides little incentive for WCDM. In contrast, fractional water allocation and capacity sharing, which has been successfully implemented in the Mazowe catchment in Zimbabwe, is presented and shown to enable more efficient, equitable and productive water use and management. Keywords: irrigation efficiency, models, fractional water allocation, water banking, mobile irrigation laboratory Introduction Uncertain water availability and a climate characterised by recurring droughts, provides strong motivation for the sugar industry in southern Africa to strive for continuous improvement in water management. For example, the sugar industry in Zimbabwe which is totally reliant on irrigation, nearly collapsed as a result of crippling water shortages following the 1991/2 drought (Binnie and Partners,1993