Development of Suitability Criteria and Hydrological Conditions Impact Assessment of Channel Reservoir in Upper Ciliwung Watershed
Penyusunan Kriteria Kesesuaian dan Kajian Dampak Pengembangan Dam Parit terhadap Kondisi Hidrologis DAS Ciliwung Hulu
Poerwanto, M Yanuar Jarwadi
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Channel reservoir is constructed to store and distribute water to the irrigated target area. The objectives were: a) characterize the parameters quality of the channel reservoir development, b) created design criteria for the suitability of the position and dimensions of individual channel reservoir in micro catchment, c) hydrological analysis for the determination of the channel reservoir capacities, quantity and distribution in watershed area, and d) to analysis the impacts of the channel reservoir development to the hydrology condition, land productivity and farmer’s income. Geologically the Cibogo sub watershed is dominated by volcanic rocks as the results of eruption of Gede-Pangrango Mountains. Physiographically the study area is classified into plated volcanic systems while the elongated hills is the dominant topography. The land use consist of: rice fields, settlements, mixed farms, tea gardens, dry land, scrub, pine forest and mixed forest. The soil is classified into Udhorthents, Hapludands, Eutrudepts, Dystrudepts, and Flufaquents. Soil Groups. Hydrologically Cibogo sub watershed has a network of rivers to upto 3th order, with a parallel drainage pattern, consists of four branches. The position and dimensions of individual channel reservoir have been prepared on the synchronization (matching) among quality/ characteristic parameters with the criteria for determining parameters. The position of channel reservoir is determined by 6 parameters: a) water availability, b) construction stability, c) accessibility, d) water distribution, e) water utilization, and 6) social condition. While the dimension is determined by: a) river cross-section, dimension of irrigation channel and irrigation target area. To simplify the process of evaluation the level of suitability and limiting factors in determining the position and dimensions DSS soft ware was developed. The soft ware is named “Expert System for the Position and Dimensions Suitability of the Individual Channel Reservoir Development (ESPADS-ICRD)”. Base on field investigation found that individual channel reservoir its influence to reducing the peaks discharge volume which between 13.2% - 48.5%, increase the land productivity from 1.5 to 2.0 to 3.0 of cropping index, and increasing the farmers income as much as 16.9 million rupiahs/ha/year. Base on historical 50 years record data of rainfall and Ciliwung river discharge’s, there are + 68 mm rain fall its equivalent to 23.4 m3 discharge with total volume 10,591,593 m3 of water must be harvested by channel reservoir construction. Its volume can be satisfied by constructing of + 663 units channel reservoirs which are spread on the second, third and fourth rivers order of upper Ciliwung watershed.