Characterisation of Groundwater in the Unconfined Aquifers of Chennai City, India. Part 1 - Hydrogeochemistry

Hydrogeochemical characterisation is a very important aspect of groundwater management. The unconfined aquifer of Chennai city is heavily exploited for meeting the water requirements of the city. Hydrogeochemical investigations carried out showed the existence of diverse hydrogeochemical facies of groundwater. Analysis of the data indicates that the quality of groundwater is related to hydrogeological environment, both in the present and the geological past. Relationship between water level fluctuations and groundwater quality in the area has been established and this is controlled by the lithology of the host rock and overlying material. The enrichment of various ionic constituents in groundwater is controlled by recharge-discharge processes as well as the local environment. Increase of TDS in groundwater after the recharge is observed in predominantly clayey areas while in sandy aquifers, it is seen to decline with recharge. The hydrogeochemistry of the groundwater shows that most of Chennai area can be classified as recharge area pointing to the dominance of vertical recharge processes.