In this method, the gross groundwater recharge is worked out by multiplying the aquifer thickness (T) with specific yield (S) of the formation and the area (A) occupied by the unit. The thickness of aquifer (T) is determined based on water table fluctuations recorded from the observation wells. The specific yield (S) of each aquifer/formation is calculated by conducting pump tests. The Groundwater Estimation Committee (GEC, 1997) has suggested certain (S) values for different rock formations but recommended to use the actual (S) values calculated from the pumping tests in the concerned areas. In hard rock areas, variations in specific yield values are so common within the same rock formation, which lead to either over-estimation or under-estimation of the resource. The studies carried out at NRSC have proved that the satellite imagery by way of providing additional information on landforms, weathering and fracturing of the rocks which account for variations in specific yield values within the same rock formation, could help in more realistic estimation of the recharge. The individual rock formation could be subdivided into more homogeneous hydrogeomorphic units taking into account the lithology, landform, fracturing and weathering characteristics derived from satellite data which further minimizes the error of averaging the aquifer parameters over large areas leading to more realistic and accurate estimation of the groundwater recharge.