Assessment of aquifer zones and its protection via second-order geoelectric indices in parts of drought-prone region of Deccan Volcanic Province, Maharashtra, India

Abstract

Assessment of aquifer protection was studied in the drought-prone regions of Mann Ganga River basin encompassing the districts of Satara, Sangli and Solapur, in Deccan Volcanic Province of Maharashtra, India, 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.