Simulating the impact of land use/land cover change and climate variability on watershed hydrology in the Upper Brantas basin, Indonesia

In this study, the impact of land use/land cover (LULC) change and climate variability on hydrological processes was assessed and simulated using the Soil and Water Assessment Tool (SWAT) in the Upper Brantas river basin, Indonesia. The Mann–Kendall (MK) test was used to analyze the spatial variations and temporal trends of the hydro-climatic variables in the basin. The model performance was assessed by using statistical indicators like coefficient of determination (R2), Nash–Sutcliffe model efficiency (NSE), the ratio of root mean square error to measured standard deviation (RSR), and percentage bias (PBIAS). These were found to be 0.905, 0.997, 0.061, and 5.7 during calibration and 0.916, 0.995, 0.071, and −6.967 during validation, respectively. During 1989–2006, LULC changes were found to be 26.12% forest, converted to 1.3% grassland, 0.03% water, 14.58% urban area, 6.77% mixed plants, and 3.44% rice fields. The integrated effects of the LULC change and climate variability decreased surface runoff, groundwater, lateral flow, and streamflow by −4.44, −2.27, −4.47, and −5.50%, respectively, but evapotranspiration (ET) increased to 0.63%. LULC change increased surface runoff by 20.14%, ET 0.03%, and streamflow 0.29%, but decreased in groundwater by −9.65% and lateral flow by −3.70%. The climate variability decreased surface runoff, groundwater, lateral flow, and streamflow by −19.07, −1.50, −0.53, and −5.78%, respectively. Both climate variability and LULC changes influence the hydrological processes. Therefore, this study recommends that the above two aspects should be taken into consideration for water resources planning and management in the study region in Indonesia. © 2017, Società Italiana di Fotogrammetria e Topografia (SIFET).