Estimation of Sustainable Aquifer Yields in the Saigon River Basin

Since the 1990s, under the pressure of socio-economic growth in Ho Chi Minh City and nearby provinces, groundwater becomes an essential resource for domestic and industrial purposes. At the same time, the surface water supply utilities still struggle to satisfy the total water demand in the developing region. The conjunctive use of surface and groundwater is an essential strategy of water supply management that has to be considered coupling with aquifer yield and surface water capability within a basin. The study aims to determine optimal intensity pumping and estimate aquifers yield within sustainable drawdown criteria. The optimal pumping intensity was analyzed from maximum existing pumping per square kilometer in four aquifers with no negative impacts on Saigon River Basin’s groundwater system. The study estimated the sustainable aquifers yield through increasing pumpage until the lowest drawdown of aquifers meets the drawdown criteria. Here, the drawdown criteria considered the groundwater pumping laws of Vietnam and the hydraulic gradient at the salinity interface. Regarding drawdown criteria and hydraulic gradient at salinity interface criteria, the drawdown constraints are –20 m. MSL for aquifer 2 and ‒30 m. MSL for aquifer 3 and aquifer 4. The simulation inputs utilized the historical 20-year climate data. According to the pumping scheme in the existing area, the optimal intensity pumping for aquifer 2, aquifer 3, and aquifer four are found to be 2000 m³/day/km², 3500 m³/day/km², and 4000 m³/day/km², respectively. Based on the optimal pumping intensity, the sustainable aquifers yield in Saigon River Basin are estimated to be at the rate of 1.9 MCM/day, which includes 57,699 m³/day from aquifer 1, 465,233 m³/day from aquifer 2, 455,151 m³/day from aquifer 3, and 925,836 m³/day from aquifer 4.