Electrical Resistivity Surveys for Groundwater in the Upper Gunjanaeru Catchment, Cuddapah District, Andhra Pradesh

Integrated geological, hydrological and geophysical (electrical resistivity) surveys have been used to delineate groundwater potential zones in Upper Gunjanaeru catchment (latitudes 13°43'45" and 14°1'44" N. and longitudes 79°15'16" and 79°27'38" E.) in Cuddapah district, Andhra Pradesh. The main lithological units in the catchment are alluvium, shales and quartzites. Preliminary pump tests in selected borewells indicate discharge variations from 6,600 lph to 48,000 lph and the respective transmissivities (T) range from 11.5 x 10⁴ lpd/m to 36 x 10⁴ lpd/m.

Forty five vertical electrical soundings were carried out using Schlumberger configuration. The data was interpreted with the help of three layer master curves and auxiliary point charts. Sounding curves suggest a few three layer geoelectrical sections H, A, K & Q type and a number of four layer sections of HK, KH, HA and AK types. Horizontal geoelectrical cross sections for selected depth levels are presented and discussed. The study indicates that the groundwater resources are mainly confined to the boulder, weathered and fractured zones in the study area except in southern parts where the groundwater is confined to the weathered and fractured zones.