Hydrogeochemical processes regulating the groundwater quality and its suitability for drinking and irrigation purpose in parts of coastal Sindhudurg District, Maharashtra

Abstract

The hydrochemistry of groundwater samples from the northern part of coastal Sindhudurg district, Maharashtra, India, was studied with an aim to comprehend its suitability for domestic and irrigation use. Groundwater samples were collected from 66 dug wells distributed over the study area, during the month of November 2017. The results of the chemical analysis indicate that the groundwater is alkaline in nature and are mainly characterized by Ca+ -Mg+2-HCO3 – , Ca+ -Mg+2-Cl– and Na+ -Cl– facies. The molar ratios of Na+ /Cl–>1, both Mg2+/Na+ and Ca2+/Na+ ratios <1, (Ca2+ + Mg2+)/ (SO4 2– + HCO3 – ) = 1 suggest that the rock-water interaction of silicates / schistose rocks (quartz, chlorite, amphibolites, schist etc.) and ion exchange reaction are the major controlling factors of groundwater chemistry. Lower molar ratios of Cl– / HCO3 –< 0.5, NO3 - /Cl-<0.3 observed reflect freshwater regime. Three samples which are in proximity to the Arabian Sea, deduce the effect of secondary contributions (saline water and anthropogenic sources). In order to determine the probable sources of groundwater contamination, principal component analysis was also carried out. The first three principal components with eigen value 1 or more are responsible for 71.31 %, 12.38% and 8.32% of the total variance in the data set, indicating major role of groundwater-rock interaction and marginal saltwater intrusion effect in the study area. Groundwater quality index computed for drinking purpose indicate that about 96% of the water samples lie within the permissible limits stipulated by the World Health Organization and Bureau of Indian Standards, and fall under the good to excellent category, suggesting its suitability for drinking purpose in the area. Water quality index indicates that most of the water is of excellent to good quality for irrigation, except for a few coastal samples.