Localized recharge processes in the NE Mekong Delta and implications for groundwater quality

Area of Science:

• Hydrogeology
• Environmental Science
• Isotope Hydrology

Background:

• Groundwater recharge is critical for Mekong Delta resources.
• Local-scale recharge processes require detailed investigation.
• Understanding impacts of rural pollution on groundwater quality is essential.

Purpose of the Study:

• To investigate localized recharge processes in the northeastern Mekong Delta.
• To assess the impact of recharge on groundwater quality using environmental tracers and pollution markers.
• To identify areas for groundwater resource protection.

Main Methods:

• Time-series analysis of environmental tracers (δ18O, δ2H, 3H).
• Measurement of major ions, ammonium (NH4), and nitrate (NO3).
• Assessment of spatial variations in recharge and groundwater chemistry.

Main Results:

• Pleistocene aquifer receives recent recharge (<60 years) during high rainfall months.
• Shallow clay layers cause spatial variations in recharge, evidenced by δ18O fluctuations.
• Recharge via acrisol soils leads to low EC, acidic conditions, and delayed nitrate contamination.
• Localized nitrogen processes result in elevated NO3 and NH4 in some areas.
• This region's groundwater is currently unaffected by arsenic contamination.

Conclusions:

• Localized recharge processes significantly influence groundwater quality in the northeastern Mekong Delta.
• Adsorption in soils delays but does not prevent nitrate contamination.
• The absence of arsenic contamination presents an opportunity for groundwater resource protection.
• Findings inform targeted strategies for safeguarding groundwater from anthropogenic activities.