Impact of climate change on Kupang River flow and hydrological extremes in Greater Pekalongan, Indonesia

Abstract

Located downstream the Kupang Catchment in Indonesia, Pekalongan faces significant land subsidence issues, leading to severe coastal flooding. This study aimed to assess the impact of climate change on future flow regimes and hydrological extremes to inform long-term water resources management strategies for the Kupang Catchment. Utilizing precipitation and air temperature data from general circulation models in the Coupled Model Intercomparison Project 6 (CMIP6) and employing bias correction techniques, the Soil and Water Assessment Tool (SWAT) hydrological model was employed to analyze climate-induced changes in hydrological fluxes, specifically streamflow. Results indicated a consistent increase in monthly streamflow during the wet season, with a substantial rise of 22.8%, alongside a slight decrease of 18.0% during the dry season. Moreover, both the frequency and severity of extremely low and high flows were projected to intensify by approximately 50% and 70%, respectively, for a 20-year return period, suggesting heightened flood and drought risks in the future. The observed declining trend in low flow, by up to 11%, indicated the potential for long-term groundwater depletion exacerbating the threat of land subsidence and coastal flooding, especially in areas with inadequate surface water management policies and infrastructure.