Analisis Debit Aliran Sungai Menggunakan Model SWAT di Sub DAS Ciasem Kabupaten Subang Jawa Barat

Abstract

Increasing developed area and decreasing forest area lead to increase runoff coefficient that further to increase the stream discharge during rainy season and draught in dry season. The hydrological model can be applied to understand that phenomena. One of them is SWAT model. Application SWAT model in this research is focused only in rainfall transformation into discharge. Research is conducted in Ciasem Sub Watershed. The aim of this research is to know the dinamics of land use change and stream discharge in Ciasem Sub Watershed, also to know the effectiveness of SWAT Model for analyzing stream discharge by using available data in Ciasem Sub Watershed. The change of land use at 2003, 2006, and 2009 particularly happened on paddy field which was changed into a mixed agricultural dryland area of about 3253,8 ha, decreased runoff coefficient. Discharge estimation using SWAT model with measured rainfall at Curugagung Rain Station as input did not fit succesfully to measured discharge at Ciasem Sub Watershed outlet. Discharge estimation using SWAT model with simulated rainfall as input results better fitting to measured discharge at Ciasem Sub Watershed outlet with the value of R² > 0,51 and NS > 0,74. The result of the simulation showed that land use change of paddy filed to mixed agricultural dryland decreased runoff coefficient from 0,21 to 0,12 and also monthly maximum runoff discharge from 117,55 m3/s to 79,68 m3/s.