The sustainability risk of Ho Chi Minh City, Vietnam, due to saltwater intrusion

Groundwater is important for domestic, industrial, and agricultural uses in Ho Chi Minh City, Vietnam. As the city has developed in a coastal environment, the issue of the fresh water supply must be solved for continuous development. The aim of this study was to quantitatively estimate the risk of groundwater salinization in the Ho Chi Minh area due to saline water intrusion into the main coastal aquifer (the Upper Pliocene aquifer) based on field monitoring data, and to evaluate the sustainability of the city with respect to groundwater resources. From the national monitoring database, water level data were obtained for the last 10 years (2000 to 2009), and a total of 33 hydrogeochemical and isotope data sets were obtained from the aquifer. The sustainability of Ho Chi Minh City with respect to the groundwater supply was quantitatively evaluated at an aquifer scale using groundwater sustainability indicators (GWSIs) suggested by the UNESCO/IAEA/IAH Working Group. The results indicated that groundwater in the southern region, part of the western region, and the area along the Saigon riverside was of poor quality, with very high total dissolved solids (>1,000 mg/L) and high concentrations of Cl and Fe, exceeding the World Health Organization’s drinking water guidelines. The Br:Cl ratios and the δ 2 H and δ 18 O values of the samples indicated that the salinization of groundwater resulted mainly from mixing with seawater over a long period. During 2004–2009, the saline boundary moved inland, with the farthest distance reaching ∼3.2 km. The long-term abstraction of groundwater, which has been much greater than its recharge capability, is probably causing the decline in water level (in 39% of the aquifer area), the degradation of groundwater quality (in 62% of the area), and the continuously expanding saline water intrusion (by 7.4% in 5 years). Thus, for the sustainable development of Ho Chi Minh City, in addition to passive measures to regulate over-pumping and pollution controls, active measures should be considered to prevent further seawater intrusion and to increase groundwater recharge through artificial recharge or better management of aquifer recharge (MAR).