APPLYING SWAT TO PREDICT IMPACT OF LANDUSE CHANGE ON HIDROLOGICAL RESPONE IN UPPER CIMANUK CATCHMENT AREA

Abstract

Cimanuk River which catchment area of 3,752 km2 is the longest river in West Java. Increasing population growth with rapid changes of other aspects such as social and economy. Based on Watershed Management (BPDAS) for Cimanuk-Citanduy data, during 1995-2003 about 400,000 trees in forest of Cimanuk catchment area were loss due to illegal logging and agriculture area demand. Landuse in upper cimanuk catchment area has changed, the most changes is conversion to settlement areas. During 1991-2002, conversion of plantation to settlement area was about 131.2 Ha, that of paddy field to settlement was 323.9 Ha, while that of un-irrigated agriculture to settlement was 91.9 Ha. The converted areas became larger in 2005, whereas plantation was 169 Ha, paddy field was 258.9 Ha and agricultural area was 274.4 Ha. Forest and paddy field areas were relatively smaller in Upper Cimanuk Catchment area. However, landuse change such as increment of the settlement or agricultural areas has a profound impact on runoff hydrographs. The general objective of the research was to develop SWAT and GIS model to investigate impact on landcover change to water yield and landuse optimization in Upper Cimanuk Catchment Area. The SWAT simulation is done during 2004 – 2005 and the validation was done for landuse 2005. The calibration of model resulted showed R2 which is 0.636 and The Nash Sutcliffe efficiency (NSE) 0.49. This simulation resulted 15.32 mm for total surface runoff and 711.2 mm for total water yield. Those numbers can infer that catchment condition was much better than the simulated landuse of 2002 condition, where the value of surface runoff was 20.75 mm and total water yield was 718.8 mm. The result SWAT simulation for 1991 was better catchment condition, where value of surface runoff was 15.3 mm and water yield was 711.2 mm.