Seite - 472 - in Book of Full Papers - Symposium Hydro Engineering

primarily for the fulfillment of raw water supply of daily necessities (raw water of DKI Jakarta and districts / cities), irrigation, industry and others. The water requirement downstream of the Ir. H. Djuanda reservoir is mainly for irrigation covering almost 87% of the total water requirement. Therefore, to determine the water requirement required the classification of irrigation water supply for Jatiluhur Irrigation Area of 240,000 ha by considering data of water availability from local sources, channel capacity and plan and condition of existing cropping pattern. The data is traced from the furthest irrigation area to the water requirement at Bendung Curug as the main building for the various needs downstream of the Ir. H. Djuanda dam by considering also the water loss in the channel and the safety factor. Water needs downstream of the Jatiluhur dam became one of the inputs in establishing the Citarum cascade reservoir operation. Some of the principles (limits) in determining the operation of the Citarum cascade reservoir are as follows: • Runoff is avoided. • Water level elevation at the end of the year is equal to or more than the water level at the beginning of the year. • The principle of equal-sharing operation, ie the proportion of clean reserves for each reservoir against the total system is constant, ie 18.8% for Saguling, 24.4% for Cirata and 56.8% for Ir. H. Djuanda. The inflow data for the three reservoirs was statistically determined using data from 1988, the year from which the Citarum cascade reservoir system began to operate fully. From the input data, optimization is done so that the maximum power production with the water requirement is fulfilled with the optimization process done by the Solver program. In operating the model, the reservoir operation model is conducted sequentially and needs to be continually updated and re-operated to obtain the most accurate forecast data on real conditions and how operational decisions are established for each component of the operation of the reservoir. With many interested parties in the operation of this Citarum cascade reservoir, the Citarum cascade operation is always evaluated and updated monthly through a coordination meeting mechanism within the coordinating team for the operation dam cascade of the Saguling, Cirata and Ir H. Djuanda (TKPBSCJ). 4.2 Economic Value of Water on Citarum Cascade Reservoir Operation. Climate change is one of the risk factors in the sustainability of the reservoir operation so it should be managed as well as possible through the deepening of climate change and its impact on reservoir operation and management of natural resources as a whole. Climate change, which can lead to changes to the hydrological regime in this case decreasing annual flow may result in a decrease in the production of hydropower generation. 472