Isotope and chemical assessment of natural water in the Jaffna Peninsula in northern Sri Lanka for groundwater development aspects.

The demand for fresh groundwater in the Jaffna peninsula in northern Sri Lanka, has been increasing as the only water source for domestic and agricultural needs. Isotopic and hydro-chemical assessment on groundwater recharge and quality was done with the objective of assisting groundwater management plans. Water samples were collected in pre and post monsoon periods for isotope analyses (H, O and H) and major ions. Isotope data provide evidence that the groundwater is predominantly recharged by inter-monsoon (convectional) and North-East monsoon rains. Different residence times of shallow groundwater were found. The study revealed that the groundwater quality is mainly deteriorated due to dissolution of geogenic elements. However, in some instances, seawater intrusion and evaporation have caused lowering of groundwater quality. More saline groundwater is found in deeper levels in the karstic limestone aquifer system. Fresh water is available in coastal sandy aquifers in the eastern part of the peninsula. The impact of rainfall variations and agricultural activities are contributory factors for producing variations in the quality of groundwater. The current study suggests artificial groundwater recharge for the development and utilization of groundwater resources through small scale tanks/reservoirs or ponds in the areas where direct rain recharge occurs.