The effect of land use changes to discharge extremities in Cimahi Watershed – Upper Citarum Watershed, West Java

The development of cities and regencies in the Cimahi watershed area increases the rate of population growth which results in high land requirements in the Cimahi watershed area. Land se change affects the flow of runoff and debit of the Cimahi River. The purpose of this research is to assess the hydrological function area in the Cimahi watershed, the impact of the land use change and to analyze the effect of landuse change in the Cimahi watershed on the extremity of water resources in terms of both quantity and quality. The natural conservation index and the actual conservation index (IKA and IKC) are used as a parameter to indicate the existing hydrological conditions and ideal hydrological conditions for conservation which are calculated based on rainfall, rock type, slope, height and land use. The results of the conservation index showed that there was a decrease in the value of the IKC from 0.637 in 2000 to 0.608 in 2012. The debit extremity could be seen based on the calculations by moving averages on the debit data, and the resulting maximum debit value was greater and the value of the base flow (baseflow) was getting smaller. Land changes in the Cimahi watershed also had an influence on the river water quality