The Change of Hydrological Regime in Upper Cikapundung Watershed, West Java Indonesia

Abstract

The changes of water movement and distribution are influenced by extreme rainfall and landcover conversions. The rainfall becomes more extreme than before. A research of hydrological regime condition is necessary to be done by managing the rainfall and river flow data. This research identifies and analyses the changes of hydrological components (rainfall, river flow, and landcover). Rainfall data obtained from 5 rainfall stations for 35 years (1978-2012), and river flow data obtained from Maribaya station for 43 years (1970-2012) in Upper Cikapundung Watershed were studied to compare the trend of older rainfall data with the newer ones. The statistical analysis employed were the correllation between area rainfall and river flow; the trend-change between maximum and minimum rainfall and river flow data; and the trend-change between baseflow and runoff coefficient C which were built from monthly rainfall and river flow data in a year. The trend-change analysis used was 5 years moving average method. It was found that the trends of 5 years moving average for Lembang, Cikapundung, and Margahayu stations were decreasing, while the other ones for Cemara and Dago Pakar stations were increasing. It was because the three first stations were located in Lembang Basin, and the last two stations were located in Bandung Basin. These changes were also supported by the changes of landcover data from 1998 to 2012. The rainfall, average river flow, and baseflow tend to decrease because the Upper Cikapundung Watershed that located in Lembang Basin had a decreased rainfall. Runoff coefficient and the river flow of Maribaya Station tend to increase due to increased maximum rainfall distribution and the land conversions.