Two dimensional modelling of electrical resistivity imaging data for assessment of saline water ingress in coastal aquifers of Sindhudurg district, Maharashtra, India

Abstract

In coastal regions, the ingress of saline water into fresh water aquifers is a threatening phenomenon. The present study using electrical resistivity imaging in parts of Sindhudurg district in coastal Maharashtra, India thus assumes signifcance in inferring the extent of saline water incursion and the underlying structures that infuence the occurrence of groundwater in basaltic rocks. The two-dimensional (2D) inversion of the feld data over 18 profles are well correlated with the available lithology. The inversion revealed the top layer consisting of alluvium/lateritic formation, followed by weathered/fractured basalts and compact basalts as bedrock. The imaging profles at places viz., 8 (Achara), 9 (Tondavali), 7 (Munge), 20 (Vijaydurg) and 12 (Wada) situated near the coast evidenced a widespread saline water intrusion. These models further indicate that there are several locations throughout the study region along the coastal part exhibiting strong salinity effect and confrmed with low resistivity values. The 2D inverted models further suggest the occurrence of aquifers mostly in weathered/fractured zones within the traps or beneath it. Also, the resistivity models divulge that the northern part of the study area represents promising aquifer zone with reasonable thickness of weathered/fractured basement.