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 (2H, 18O and 3H) 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.

Assessing causes of quality deterioration of groundwater in Puttalam, Sri Lanka, using isotope and hydrochemical tools.

Extensive extraction of groundwater has resulted in deterioration of the groundwater quality in the Puttalam area in the northwestern coastal zone of Sri Lanka. This situation led us to carry out the present comprehensive study based on environmental isotopic ((18)O, (2)H, (3)H) and geochemical evaluation to understand the root cause for water quality deterioration. The isotopic data suggest that the surface water and shallow groundwaters are subjected to intensive evaporation and, as a result, increase in their salinity. Deep groundwater of the area is mostly recharged by direct infiltration of rainwater and at few places by nearby surface water bodies. The salinity increase of deep groundwater depends on the specific hydrogeological zones and would be due to dissolution of salts which are precipitated in soil through the seawater spray over the time, dissolution of minerals in geological matrix and leaching of salts from salterns. The quality of the deep groundwater is relatively good in the granitic gneiss zone and nearby areas outside the sedimentary aquifer. There is no evidence from isotope and hydrogeochemical evaluation for seawater intrusion into groundwater in the Puttalam area.