Delineation of Shallow Groundwater Aquifer in the Piedmont Area (Uttaranchal –India) Using Surface Resistivity and Hydrogeological Data

Seventy vertical electrical soundings (ves) have been conducted in the study area using schlumberger configuration with maximum electrode spacing (ab/2) of about 900 m and at the station interval of about 2 km and less. an automatic computerized interpretation method has been used to obtain true resistivity and layer depth from the measured apparent resistivity data at each site. for the geological interpretation, the resistivity values are correlated with the known lithology from available borehole data in the study area. this correlation helps in defining the resistivity ranges for various layers in the area which ranging 22 -165 ohm-m.the lattest indicate water bearing sand with gravel and form the shallow aquifer in the bhabhar and tarai zones.the thickness of this aquifer varies between 2 to 8m in the bhabhar and 5 to15 m in the tarai. the depth to the shallow aquifer zone varies from 17 to 32 m in the foothills (bhabhar zone) and 1 m to 7 m in the tarai. due to occurrence of the finer materials in the tarai belt, the groundwater occurs under confined, semi- confined and unconfined condition.