| Abstrak/Abstract |
Water utilization for irrigation purpose through reservoir operation often faces problems in the form of uncertainty in water potential either in the amount or in the distribution pattern of flow from water sources. This issue is found in Pandanduri Reservoir, West Nusantara Province, Indonesia, where a unique mechanism of water reuse persists in which the return flow from drainage system and pond is used for irrigation water supply in the downstream cultivated area. Ddetermination of water allocation based on the water availability according to time and space distribution should be considered in formulating an optimal reservoir operating rule. In this research, a multi-criteria water allocation model was developed to optimize the performance of the reservoir operation in fulfilling irrigation water demand. Standard operating rule method of reservoir simulation was applied in combination with a deterministic linear programming model to control release from the reservoir. The criteria used to measure the performance of water allocation are annual cropping intensity, k factor as the ratio between actual release and target release according to water demand, and the reliability of reservoir operation. The result shows that the distribution of return flow discharge can be estimated with a simple Tank model. The optimum reservoir operation concludes that irrigation water supply capacity is characterized by average k factor of 0.87 and the reservoir operation reliability is 83%. Moreover, the consistency of the performance of water allocation model was verified using reservoir operation simulation model with input of the generated synthetic stream flows. |
