Hydrochemistry and isotope data from groundwater monitoring wells in the Mekong Delta, Vietnam

A total of 119 groundwater samples were collected across the Mekong Delta in Vietnam for hydrochemical and isotopic analysis (major ions, secondary elements, δ2H-H2O, δ18O-H2O, δ13C-DIC, 14C-DIC). The campaign comprised samples from five deep, (semi-)confined aquifers of the Mekong Delta and was conducted in March and April 2021 at monitoring wells of the National Groundwater Monitoring Network in cooperation with the Division of Water Resources Planning and Investigation in the South of Vietnam (DWRPIS). At each well, about three well volumes of groundwater were pumped with a submersible pump and field parameters were measured using a flow cell. A set of five bottles was taken for analysis of cations and secondary elements (PET), anions and alkalinity (PET), dissolved organic carbon (DOC) (glass with aluminum cap), stable isotopes of water (glass), and carbon isotopes (HDPE). Water for cations and secondary elements was passed through 0.45 µm cellulose acetate filters and acidified with ultrapure nitric acid (Merck) to pH<2. The main objective of the project was to assess the impact of groundwater abstraction on groundwater flow and water quality in the different aquifers.