Chemical Characteristics of Surface Water and Groundwater in Coastal Watershed, Mekong Delta, Vietnam

The objective of this research was to provide hydrological and stable isotopic information to figure out the characteristics of surface water and groundwater in Cu Lao Dung (CLD) Island, a coastal area in the Mekong Delta, South of Vietnam. Water samples were collected in March 2013 during the driest period of the year. The basic tracing elements of water showed that groundwater was characterized by fresh water of Ca-HCO3 type, whilst almost river and canal water samples were categorized in saline water of Na-Cl type. Groundwater is only fresh water source for drinking purpose in this area, because river and canal water cannot be used for that due to serious seawater intrusion. Moreover, the results of inorganic solute concentration and stable isotopic compositions suggest that currently, interaction between river/canal water and groundwater may not occur in CLD Island. This implies that main recharge areas of the groundwater seem to be located outside of the CLD Island. For sustainable groundwater pumping, an appropriate management is necessary in the coastal areas in the Mekong Delta; more investigation, not only in small areas but also in large scale of Mekong Delta, is needed.