Impact of landuse on the groundwater quality along coastal aquifer of Thiruvallur district, South India

The present study was carried out to understand the impact of landuse pattern that includes agricultural and urban development on coastal aquifers of the SE coast of India. Regional geology includes marine sediments, alluvium, sandstone and laterite formations. Groundwater samples were collected from 50 dug wells and bore wells during pre-monsoon 2013 (May) and post-monsoon 2014 (January). Water samples were analyzed for physical and chemical parameters such as electrical conductivity (EC), pH, TDS, Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, HCO₃ ⁻, SO₄ ²⁻, NO₃ ⁻ and Total Hardness, using standard procedures. Results indicate the following order of concentration of ions: Na⁺ > Ca²⁺ > Mg²⁺ > K⁺, and Cl⁻ > HCO₃ ⁻ > SO₄ ²⁻ > NO₃ ⁻. Further, total hardness (TH) was evaluated to understand the suitability of groundwater for drinking purpose. Na–Cl, Mixed Ca–Mg–Cl and Ca–HCO₃ facies were the dominant groundwater types in the study area. Study findings gives a detail understanding of interrelations between geology and landuse practices with water quality. Statistical results indicate that leaching of secondary salts, sea water intrusion, infiltration of contaminated water and ion exchange processes are responsible for the groundwater chemistry variation.