Evaluasi Perubahan Penggunaan Lahan dan Pengaruhnya Terhadap Karakteristik Hidrologi DAS Citarum Hulu

Abstract

Currently mayority of watersheds in Indonesia have suffered a lot of decreased function in maintaining water availability and environmental health, one of which is citarum watershed. Land use changes in the Citarum watershed are very intensive, especially in the upstream part. The upstream watershed plays an important role as a water absorbtion area and a buffer zone for the downstream area. The research was conducted in the upper Citarum watershed covering an area of 175,158.9 hectares with the outlet at Nanjung stream monitoring station, which aims to analyze land use changes on hydrological characteristics in the upper Citarum watershed, and formulate land use direction in the upper Citarum watershed that are able to preserve the hydrological function of the watershed. The research were devided to; (1) visual interpretation of SPOT image data; (2) analysis of land use changes; (3) hydrological response analysis of river discharge; (4) analysis of the effect of land use changes on river discharge; (5) analysis of the suitability of upper citarum watershed spatial pattern to spatial plans of West Java. Spot image interpretation can be done well as shown by the Overall Accuracy (OA) coefficient of 93.33% and Kappa Accuracy (KA) of 90.6%. The results of the analysis of the map of land use changes in the upper Citarum watershed in the period 2009 - 2018 showed an increase in vacant land (+95%), developed land (39.7%), rice field (+13%), and plantations (+6.4%). The increase was accompanied by a decrease in bushland (-60%), rice fields (-17.4%), and forests (-5.5%). The percentage of suitability of the existing land is 59.6% suitable and 40.7% not in accordance with the spatial pattern of the West Java spatial plans. The results of hydrological response evaluation show that the Ciwidey, Cisangkuy, and Cihaur sub-watersheds are classified as first priority to be restored it’s hydological response entirely. Second Priority is Cirasea, Cikeruh, and Cikapundung sub-watersheds, where efforts to restore hydrological response are gradual. Where as the Citarik sub-watershed is classified as third priority that the hydrological conditions must be maintained. The application of land conservation that combines vegetative and physical conservation is aimed at types of land use that do not match the area's spatial pattern. The management and utilization of agricultural and plantation land by applying agroforestry systems, intercropping and terracing along with the application of a zero runoff system in built-up land is expected to improve the hydrological response of the Upper Citarum Watershed.