Optimization of Water Distribution to Support the Balance of Water Usage: A Case Study of the Sempor Irrigation System, Central Java, Indonesia

The existence of irrigation in Indonesia is commonly quite influenced by environmental and social cultural characteristics, which the people have lived by and developed for a long time. Many factors cause changes in the pattern of water availability, which increases competition among stakeholders, as in the Sempor irrigation system area. It has four main dams, which are the Bojong Dam, Watubarut Dam, Rowokawuk Dam, and Sindut Dam; it provides approximately 5900 ha of services and receives supplies from the Great Sempor Dam (38 million m3). Currently there is a decline in the function of this dam due to sedimentation, making operational services less optimal, especially during the dry season. The methodology of this study is to perform water optimization for the balancing of water in the irrigation area. Meanwhile, the implementation of the water supply on the field considers the calculation of water availability, space, and time. In practice, the operation of water supply is held by a group system in the secondary blocks. In certain conditions, the water rotation in tertiary channels was performed by local cultural wisdom.