Hydrological subsurface investigation using geophysical electrical and magnetic methods in and around Valliyar river basin, India

The focus of the present study is to identify potential groundwater zones using resistivity Schlumberger array and magnetic method for mapping hidden lineaments in and around the Valliyar river basin situated in the tail of Southern India. Estimation by 2-D radial power spectrum indicates that the maximum depth at which the magnetic source is present is about 700 m to 800 m. In case of shallow depth magnetic source rock, it is about 40 m to 45 m. The results of magnetic data have revealed the presence of a major magnetic lineament trending in NW to SE direction. The electrical resistivity survey in our study area gives information on sub-surface layers like the weathered zone, aquifer resistivity and aquifer thickness. The locations corresponding to ves-35, ves-40, and ves-47 have weathered and fracture layers having a thickness greater than 20 m, situated in the magnetic major lineament trend. Regarding master curves for layer analysis, H and HA type curves are generally observed in the hard rock region. The interpretation of results from the present study endorses that the coastal region of the study area has good groundwater potential.