Geoelectrical Study for Groundwater Resources in Parts of the Ahmedabad and Gandhinagar Cities, Gujarat, India

The central alluvial plains of Gujarat, western India, consist of deposits of north–south flowing rivers from the Aravalli hills. The Gandhinagar and Ahmedabad districts in the state form a part of the Cambay basin and are occupied by Quaternary alluvium comprising mainly of sand, gravel, silt clay, kankar, etc. Direct current (DC) electrical resistivity studies have been carried out at six sites in Gandhinagar and Ahmedabad cities to map ground­water levels and major shallow subsurface geo­electric layers using a 72-electrode resistivity imaging system. Two dimensional (2D) resistivity models and bore­hole data infer a multilayered aquifer system in Ahmeda­bad. The top confined aquifer is at a depth of 22–25 m and the second unconfined aquifer is at a 60–65 m depth. These two aquifers are separated by highly com­pacted clay/clayey sand. For the two locations in Ahmedabad city, the 2D resistivity model suggests 10–15 m variation in the groundwater level. In Gandhinagar, as the survey location is close to the Sabarmati River and the exploitation of groundwater is less than in Ahmedabad, the groundwater table is at shallow level. Further, the resistivity estimates suggest that, at all three locations, the groundwater is moderately saline. The infer resistivity sections are correlated with groundwater level and borehole data