Water resources management policy evaluation in the Brantas Basin, East Java, Indonesia

We describe the application of an integrated economic-agronomic-hydrologic river basin policy simulation model, intended to assist water managers in designing and evaluating strategies for improving the physical and economic productivity of water. The model is specified for the Brantas Basin in East Java, Indonesia, a densely populated catchment of 12,000 km ² containing extensive irrigated agriculture. The Brantas is seasonally water constrained, and municipal and industrial users compete with irrigated agriculture, and with environmental quality demands, for increasingly scarce water. As options for supply augmentation in the Brantas are limited, water managers will depend increasingly on demand management strategies, particularly those effective in limiting irrigation abstraction. We describe the results of three simulation scenarios, including the introduction of volumetric water charges, the reduction of paddy and sugarcane price supports, and the introduction of formal water use rights in combination with market instruments. The effectiveness of these policies is evaluated on the basis of two criteria: the extent to which net irrigation withdrawals are reduced, particularly during the dry season, and the financial impact on the irrigation sector. We discuss key policy findings based on the results of these scenarios.