(Proceedings of Symposium HS1001 at IUGG2007, Perugia, July 2007 – IAHS Publication 312, 2007 pp. 50)
Integrated geoelectric and geochemical investigation were carried out in the Sagar Island region to assess the prevailing groundwater conditions and chemical quality of groundwater. Geologically, the area is constituted of alluvial and marine sediments of Quaternary age. Vertical electrical soundings (VES) in the area of investigation mostly show five layers consisting of topsoil, saline water, brackish water, a clay layer and freshwater-bearing zones. The VES findings show the potential freshwater-bearing zone to be of appreciable thickness at depths of 175.0 to 220.0 m under confined conditions. The surface true Resistivity contour map shows the intrusion of saline water in the southern part of Sagar Island at shallower depths. The results of VES studies significantly correspond with the borehole data. Chemically, the fresh groundwater is Na-HCO3 type with TDS ranging from 465 to 645 mg/L. The water is safe for drinking and domestic purposes but unsuitable for irrigation purposes. The concentrations of arsenic, iron, lead and mercury in the samples are below the recommended limit for drinking water of the World Health Organization (WHO).
Sagar island, Vertical electric sounding (VES), Litho-resistivity relation, Seawater contamination (SWC), Freshwater aquifer
