KAJIAN PENGEMBANGAN PENGELOLAAN SUMBERDAYA AIR PADAWILAYAH SUNGAI PROGO-OPAK SERANG DENGAN RIBASIM

Abstract

Land use change in Progo-Opak-Serang (POS) River Basin has caused hydrologic behavior change, which it is shown by the flooding events during the rainy season, and the lack of water allocation during the dry season. To anticipate hydrologic behavior and water demand changes in the future, integrated water resources managements in Progo-Opak-Serang (POS) River Basin, should be elaborated in the arrangement as well as development program. Water resources allocations of the Progo-Opak-Serang (POS) River Basin at the present time (in the year of 2005) and in the future (i.e. in the year of 2015 and 2025) which are based on several difference developement scenarios were analysed and modeled by using RIBASIM Software. Calculation of water resources allocation was carried out by dividing the POS River Basin area into 52 water districts. Water balance analysis show there is surplus of water in most of water districts in Progo-Opak-Serang River Basin during the rainy season, and some of them are shortage of water during the dry season The highest water demand of POS River Basin is used for irrigation, which achieves to 82 % of total water demands, while for MDI (Municipal, Domestic, and Industry) achieves to 17.6 %, and fish pond, 0.4 %. By applying several scenarios of water resources development managements, i.e., by increasing the irrigation efficiency at about 5 %, rearranging the planting cultivation, and providing a new reservoir in down stream Progo River basin, i.e, Tinalah reservoir, the deficit of water balance during the dry season can be reduced significantly.