Groundwater Investigations in Parts of Alwar District, Rajasthan

Geohydrological investigations including deep resistivity Schlumberger soundings were carried out to locate suitable drilling sites for groundwater expIoitation near Ramgarh, Alwar district, Rajasthan. The area under study appears to be a synclinal valley and is covered by a thick piIe of sediments comprising sand, silt, clay, gravel, pebble, kankar and scree underlain by rocks of Ajabgarb Group, which are exposed north-west of the area. The subsurface layer parameters obtained from the sounding interpretation have been presented in the form of fence diagrams and a geoelectric section. Characteristic resistivities of various litho-units were obtained by correlating the lithology of an existing tube well with the geoelectrical sounding data. The correlation indicated that there is very little resistivity contrast between water-bearing sandy layers and the kankar and clay beds. However, the kankar and clay beds are mostly confined to the top 20 m or so. Although occurrence of clay has not been reported in rocks of Ajabgarh Group except for thin lenses, the present investigations reveal a surprisingly low resistivity for the formation underlying the bedrock, which may be an indication of its saline and clayey nature. The possibility of an altered horizon in the bedrock comprising metasediment through lateral inflow of water cannot be ruIed out.