Hydrogeochemical Characteristics of Groundwater Influenced by Seawater Intrusion in Coastal Aquifer of Guhagar, Ratnagiri District, Maharashtra (India)

Groundwater is the main source of drinking in coastal areas and the gradually decline in its quality is a most important issues. The aim of present study is to assess the groundwater quality and its deterioration in coastal aquifer in Guhagar area of Ratnagiri District, Maharashtra (India) by examining the hydrogeochemical characteristics. A total 25 water samples were collected from three different zones from the study area viz. seawater, backwater and groundwater, apart from this one surface water sample during the winter season. Samples were analyzed for its physicochemical parameters (i.e., pH, EC, TDS, Ca2+, Mg2+, Na+, K+, Cl–, SO42–, CO32– and HCO3–) and selective trace elements such as Cd and Pb. The majority of the observed chemical parameters of all groundwater samples are within the permissible limit of the BIS water quality standards except pH, potassium and lead while WQI values indicate that the water quality is very poor to unsuitable category. The Cd and Pb concentrations in seawater and backwater are observed beyond the permissible limits. Generally established plots such as USSL plots, Gibbs plot, Bivariate plots and molar ratios such as sodium/chloride and chloride/bicarbonate were used to identify the seawater intrusion into the coastal aquifers. The suitability of groundwater for irrigation was evaluated based on sodium adsorption ratio (SAR), soluble sodium percentage (SSP), residual sodium carbonate (RSC), Permeability index (PI), Corrosivity ratio, sodium percentage (Na %) suggests that the most of the groundwater is suitable for irrigation purposes. Seawater ingression, ionic ratios and difference in groundwater geochemistry during the high and low tides indicate that the moderate effect of seawater. Keywords Seawater intrusion, groundwater, coastal aquifer, Guhagar, India.