Pengaruh Perubahan Penutupan/Penggunaan Lahan terhadap Karakteristik Hidrologi Sub DAS Ciliwung Hulu

Abstract

Watershed is an ecosystem consisting of upstream, middle and downstream. Upstream watershed ecosystem is play an important role, because its function to regulate hydrologic characteristics of the watershed. Ciliwung watershed is one of the superpriority watershed that must be taken high priority effort to rehabilitation. According to Suripin (2002), hydrological components affected by development activities in the watershed includes surface flow coefficient, coefficient of discharge regim river, the ratio between maximumminimum river discharge, mud content or sedimentary deposits in the river, the rate of frequency and period of floods, and also the state of groundwater. The aim of the research is to analyze land use/cover, changes of land use/cover in upstream ciliwung watershed and to analyze its influence on watershed hydrology (flood and maximum-minimum river discharge). In this research landsat image of 1990, 2001 and 2010 was used to analyze the land use/cover changes. After that the condition of land use changes and characteristics of watershed hydrology were compared and evaluated. Based on image interpretation of land cover in 1990 and 2001, the area dominated respectively by dense jungle, mixed farms and tea plantation. While land use in 2010 is dominated respectively by dense jungle, tea plantation and settlement. Patterns of land use/cover change at period 1990-2001 indicates substantially conversion of agriculture land such as the rice field, dryland farming and mixed farms into settlements. Area that converted respectively are 238.8 ha, 238,5 ha and 127,8 ha. Bush land is transformed into agriculture land as well, which are tea plantation (180,1 ha), mixed farms (140,7 ha) and other agricultural cultivation. Mixed farms is the most intensively converted land into dryland farming (411,3 ha). In the period 2001-2010, pattern of landuse/cover changes that occured is not too different but in a much larger scale. Large conversion of agriculture land occurred toward settlement (rice field 231,3 ha, mixed farms 176,2ha and dryland farming 128,9 ha). Mixed farms was converted into dryland v farming are 329,5 ha and rice field 212,8 ha. Amount of bush land converted to tea plantation, rice field and dryland farming were respectivally 107,1 ha, 144,9 ha and 108,4 ha. A decline in the quality of the upstream ciliwung watershed hydrology can be seen from characteristic of flood frequency, the quality of a flood, maximum-minimum river discharge and the ratio between maximumminimum river discharge. Increase of settlement and dryland farming area in the upstream ciliwung watershed contribute to declining of upstream ciliwung sub watershed hydrology characteristics.