Delineation of Groundwater Potential and Recharge Zone Using Electrical Resistivity Method Around Veeranam Tank, Tamil Nadu, India

Abstract

Veeranam tank is one of the largest tank in Tamil Nadu, India which plays a vital role in groundwater recharge to the surrounding aquifer. Electrical resistivity survey were carried out in ten locations around the Veeranam tank. The resistivity, thickness of subsurface formations, longitudinal conductance (S), transverse resistance (R), average longitudinal resistivity (ST), average transverse resistivity (RT) and anisotropy (λ) were used to characterize the lithological formations and also groundwater potential and recharge zones were delineated. The four major zones clay, clayey sand, saline sand and sandstone were identified as a result of primary geo-electrical parameters which includes resistivity and thickness of the formations. The sandstone formation is identified as good water bearing formation and this formation possess low longitudinal conductance, high transverse resistance, and low anisotropy values. The clay and saline formation possess high longitudinal conductance, low transverse resistance and high anisotropy values and these formations are identified as moderate groundwater water bearing formations. High longitudinal conductance is observed in eastern region of the study area due to intrusion of saline water. Sandstone formation of low longitudinal conductance is associated with high percolation rate and groundwater potential is also good in this formation. High transverse resistance zones are associated with high infiltration rate and high transmissivity whereas groundwater potential is good in these zones. VES 2 and VES 3 stations comprises of sandstone formation as second layer and Veeranam tank water infiltrated into these zones due to high infiltration rate of these formations. The resistivity value is decreased in VES 10 station due to intrusion of sea water. The true resistivity near the Veeranam tank is high and decreases towards east which clearly indicates that groundwater recharge is the major process that occurs nearby the downstream shore of tank and intrusion of saline water in the eastern part of the study area. Thus good interaction between exists between Veeranam tank and its downstream zones and interaction decreases as the distance increases from the tank.