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, using electrical resistivity technique. The study was also aimed at alleviating the drinking water scarcity in these regions. A total of 118 vertical electrical sounding sites were occupied using Schlumberger electrode configuration and the data analysis revealed two to five layered curve types. The modelled layer resistivity and layer thickness at every station were used to calculate the Dar-Zarrouk parameters (i.e., longitudinal conductance S and transverse resistance T). The S values showed that 67% of the area had a poor aquifer protection, whereas 16% had moderate protective capacity and 13% had weak aquifer protective capacity rating. Only 4% of the study area depicted a good protective capacity rating. This indicates that the study area has a rather poor aquifer protective capacity rating, and thereby more prone to infiltrating contaminants. The regions with good-to-moderate protective capacity are envisaged to be potential groundwater zones. The large variation in electrical anisotropy λ ranging from 1 to 2.8 in the study area suggests the anisotropic disposition of the aquifers in basaltic region. The intersection points of several lineaments in the study area are probable to be the most favourable zone for groundwater recharge. This is corroborated by the lineament density of the area, wherein high lineament density reflects high probability of groundwater infiltration. Moreover, the rainfall distribution suggests that the central and eastern parts of the study area receive maximum precipitation, which also coincides with the zones of high lineament density. Particle size analysis was determined from 92 soil samples in the study area and correlated with the longitudinal conductance in order to identify the sub-surface conditions and the aquifer vulnerability. Significant positive correlation was observed between the longitudinal conductance and percentage of clay fraction in the study area. These results could be relied upon for making preliminary estimates of protection from pollution for a sustainable groundwater development and management in future.

The present study focuses on the occurrence and intensity of fluoride in drinking water from the Malvan-Vijaydurg coastal tract in Sindhudurg district, Maharashtra. Concentration of fluoride (F-) from 36 dug wells/bore wells sampled during this study ranged from 0.04 mg/L to 1.6 mg/L. The results indicate that about 47% of the water samples from the study area have fluoride content greater than 1 mg/L, which exceeds the permissible limit of BIS (1 mg/L), while 4 samples exceeded the World Health Organization standards of 1.5 mg/L. Spatial variation in F- concentration indicates that most of the sampling sites having comparatively high fluoride also have high values of pH, EC and TDS concentration measured in groundwater. High fluoride levels are associated with Ca-Mg-Cl-SO4, Na-Cl and Na-HCO3 type water produced by calcite precipitation and/or base ion exchange. The groundwater with higher fluoride concentrations is accompanied by lower Ca+2 levels. This study augments our understanding on geochemical behaviour of F- concentration and highlights the importance of spatial variability of F- in coastal aquifers. It is also pertinent to monitor the water quality periodically in this region and consequently discontinue using the wells which contain high fluoride concentration.

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