Impacts of water supply leakage and inter-basin water transfer on groundwater dynamics in Greater Jakarta

Study region: Greater Jakarta in the Ciliwung-Cisadane River basin, Indonesia Study focus: Over 80 % of Jakarta's domestic water supply is imported from the Citarum River basin. Although this supply theoretically meets 65 % of current domestic water demand, approximately 46.67 % is lost through pipeline leakage. Given the large volumes involved, both leakage and inter-basin water transfer (IBWT) must be explicitly accounted in simulating Jakarta's hydrology and water resources. New hydrological insight for this region: This study presents a refined framework for assessing water allocation and groundwater management in urbanized basins by integrating domestic water supply leakage and IBWT into a distributed hydrological model. Simulations were conducted for the Ciliwung-Cisadane River basin, covering Jakarta, at 30-arcsecond (∼1 km) resolution for the 2004–2013 period. Two leakage mechanisms were modeled: (1) LEAK1, where leakage directly recharges groundwater, and (2) LEAK2, where leakage first infiltrates the soil layer. Multiple scenarios were analyzed, including a baseline condition, leakage influence, and IBWT effects. Results show that leakage contributes 35 %-41 % (95 % confidence interval) of total groundwater recharge, with higher contributions in urban areas. IBWT reduces Jakarta's domestic water deficit by 62.5 % and increases leakage volume by 12 %. The simulations also reveal an urban groundwater recycling process in which leaked water initially intended for domestic use is unintentionally reallocated to support industrial groundwater extraction. By explicitly incorporating these urban hydrological processes, this study provides more realistic, policy-relevant insights for sustainable water resources management.