Assessment of seawater mixing in a coastal aquifer

Authors: S Sathish L Elango R Rajesh V S Sarma

Publish Date: 2011/06/01

Volume: 8, Issue: 3, Pages: 483-492

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Abstract

Seawater intrusion is a major problem in urbanized coastal regions of India which is due to over exploitation of groundwater for various purposes This study was carried out with the objective of assessing the zone of mixing between seawater and groundwater in the coastal aquifer in south of Chennai Tamil Nadu India using high resolution electrical resistivity tomography High resolution electrical resistivity tomography was carried out in five profiles perpendicular to the sea using IRIS make SYSCAL Pro96 system with 25 m or 5 m interelectrode separation The maximum length of the profile was 170 m which resulted in a depth of investigation of 287 m The apparent resistivity measured in this area varies from 03 ohmm to 30000 ohmm The apparent resistivity of saturated zone decreases towards the sea indicating the influence of seawater This was also confirmed by measuring the electrical conductivity of groundwater which gradually increases from 156 μS/cm to 3430 μS/cm towards the sea Further the concentration profiles of electrical conductivity sodium chloride and chloride / bicarbonate ratio are compared with the high resolution electrical resistivity tomography profile The distance of influence of seawater is comparatively high in northern part than in southern part of the area The high resolution electrical resistivity tomography was effectively used to determine the effect of seawater mixing with groundwater

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