Attribution of changes in stream flow to land use change and climate change in a mesoscale tropical catchment in Java, Indonesia

Changes in the stream flow of the Samin catchment (277.9 km²) in Java, Indonesia, have been attributed to land use change and climate change. Hydroclimatic data covering the period 1990-2013 and land use data acquired from Landsat satellite imageries for the years 1994 and 2013 were analysed. A quantitative measure is developed to attribute stream flow changes to land use and climate changes based on the changes in the proportion of excess water relative to changes in the proportion of excess energy. The results show that 72% of the increase in stream flow might be attributed to land use change. The results are validated by a land use change analysis and two statistical trend analyses namely the Mann-Kendall trend analysis and Sen's slope estimator for mean annual discharge, rainfall and potential evapotranspiration. The results of the statistical trend analysis are in the same direction as the results of the attribution analysis, where climate change was relatively minor compared to significant land uses change due to deforestation during the period 1994-2013. We conclude that changes in stream flow can be mainly attributed to land use change rather than climate change for the study catchment.