Evaluation of Groundwater Quality and Effects of Exploitation on Static Groundwater Levels in Dong Thap Province, Viet Nam

Groundwater is an important natural resource used for drinking, agriculture, and domestic use in the Mekong River Basin. In this study, the groundwater quality and storage were evaluated in Dong Thap province from 2010 to 2023. Results showed that most groundwater samples contained major indicators such as $${\text{SO}}_{4}^{{2 - }}$$ , N– $${\text{NO}}_{3}^{ - }$$ , N– $${\text{NO}}_{2}^{ - }$$ , Cl– and Fe while more than 70% of samples were detected with Mn2+, Pb, Cu, Zn, Cd, Hg and coliform. Notably, some parameters, i.e., Cl–, Mn2+, Fe, E. coli and coliform had significant samples above the permissible limits. The calculation of groundwater quality index (GWQI) showed that GWQI was very good and good quality was observed in most boreholes at different aquifers. We observed GWQI values were lowest in 2016 and highest in 2021. Average concentrations of most water parameters were lower in the Lower Pliocene and Miocene aquifers (depth layers), while they were higher in the Holocene aquifer due to the effects surface water in which pollutants were produced from domestic and other purposes. Moreover, the differences in concentrations of most parameters in dry and rainy seasons were only found in the Holocene aquifer. The geological and hydrogeological conditions also impacted the hydrogeochemical characteristics. Declining trends of the static groundwater levels were found in Tam Nong and Thap Muoi districts from 2010 through 2023, indicating a decrease in groundwater storage, especially in the Lower Pliocene aquifer. This study provides valuable information for the future management of groundwater quality and abstraction.