Eri’s Limited Role for Groundwater Exploration in Hard Rock with Underground Utilities and Micro-Gravity

In the presence of underground utilities coupled with the fracture controlled groundwater exploration is a formidable task for Electrical Resistivity Imaging (ERI) in the hard rock region of coastal Orissa having high resistive dry laterite soil underlain by khondolites and granites at depth, India. Based on regional lineaments in space imagery of study region aided by regional gravity trends, micro-gravity (N-S profiles) and feasible ERI data acquisition on IIT BBS were done. For decomposition of acquired micro-gravity we used the aquifers identified in a drilled borehole and assessed the total groundwater reserves. A lone ERI profile at the periphery of IIT BBS aided by micro-gravity have identified a fault at a depth of 20m and it serves as groundwater aquifer at shallow depth; however, deeper aquifers do not clearly appear in ERI due to low depth resolution, but the total gravity signal along the same profile can be decomposed into its components with the drilled borehole aquifer information as constraint. This task is left for future groundwater tapping. However, towards the anomaly decomposition advantage of micro-gravity, we illustrate identification of groundwater bearing fractures within IIT Bhubaneswar (IIT BBS) campus with underground utilities within Eastern Ghat Mobile Belt (EGMB) region of coastal Orissa. We could also estimate the amount of groundwater held by inferred fracture zones by using both the gravity models and residual gravity to be at least 11GL within the campus. We have also demonstrated the success of outlined methodology at a site close to IIT BBS campus by drilling results and those results are not included here. The outlined integrated micro-gravity and ERT methodology can be extended to the groundwater exploration of hard rock regions of Odisha state, India.