The Impact of Land Use and Land Cover Change on Hydrological Processes in Brantas Watershed, East Java, Indonesia

Abstract

Assessing the impact of land use and land cover change (LULCC) on hydrology is essential for water resource management. The Brantas watershed contributes about 30% of the water supply of the East Java region. The present rapid pace of land occupation for agricultureand settlementsis expected to continue to alterflow processeswithin thewatershed. This study aims to simulateLULCCand its impact onthe hydrological processesof the watershed. The long-termimpact of LULCCis evaluated using the Soil & Water Assessment Tool (SWAT). The analysis model is calibrated using monthly data series from 1996 to 2005 and then validated using data seriesfrom 2006 to 2015. Two editionsof maps(2001 and 2015)are then used to calculate the LULCCthat took place across this time period.The impactsof LULCCon hydrological processes at the sub-basin level are also evaluated. The results show that the variability of rainfall patternsfrom 2001 to 2015strongly affectedflow variability.The LULCCfrom agricultural land to otheruses(irrigated ricefields, settlementsand forests/plantations) is mostevident in three sub-basins(sub-basins2,9 and 17). However,eachsub-basin mayrespond differently with respectto theLULCCtaking place.The increase inarea occupied by eachclassof land use and coveruse(LULC)is not always linear to the observed flow, and widely differingLULC classesmay display similarflowresponseswhileclasseswith similar characteristics may havediffering impacts onflowswithin a sub-basin. In other words, the hydrological processes taking place aretoo complex to be simplified at thesub-basinlevel.