The impact of future climate projections and anthropogenic activities on basin-scale groundwater availability

Abstract

Abstract. Groundwater is under the pressure of changing climate and increasing anthropogenic demand. In this study, we project the effect of these two processes on the projected future groundwater status. Climate projections of Representative Concentration Pathway (RCP) 4.5 and RCP8.5 from the Coupled Model Intercomparison Project Phase 6 (CMIP6) drive a one-way coupled fully distributed hydrological and groundwater model. In addition, three plausible groundwater abstraction scenarios with diverging predictions from increasing, constant, to decreasing volumes and spatial distribution are used. Groundwater status projections are assessed for the short-term (2030), mid-term (2050), and long-term (2100) periods. We use the Bandung groundwater basin as our study case, located 120 km from the current capital city of Indonesia, Jakarta, which is currently under a relocation plan. It is selected as the future anthropogenic uncertainties in the basin, related to the projected groundwater abstraction, is in agreement with our developed scenarios. Results show that changes in the projected climate input, including intensifying rainfall and rising temperature, do not propagate notable changes in groundwater recharge. Under the current unsustainable groundwater abstraction rate, the confined piezometric heads are projected to drop up to a maximum of 7.14 m, 15.25 m, and 29.51 m in 2030, 2050, and 2100, respectively. When groundwater abstraction expands in proportion to the present population growth, the impact is worsened almost two-fold. In contrast, if the groundwater abstraction decreases because of the relocated capital city, the groundwater storage starts to show replenishment potential. As a whole, projected groundwater status changes are dominated by anthropogenic activity, and less so by changes in climatic forcing. The results of this study are expected to demonstrate and inform responsible parties in operational water management on the issue of the impact of projected climate forcing and anthropogenic activity on future groundwater status.