The Ministry of Water Resources, Govt. of India, therefore, constituted a committee consisting of experts in the field of ground water to recommend a revised methodology. This report is the final outcome of the recommendations of the Committee. The revised methodology as recommended has incorporated number of changes compared to the recommendations of Ground Water Estimation Committee - 1997. The revised methodology GEC 2015 recommends aquifer wise ground water resource assessment to which demarcation of lateral as well as vertical extent and disposition of different aquifers is pre-requisite. However, it is recommended that ground water resources may be assessed to a depth of 100m in hard rock areas and 300m in soft rock areas till the aquifer geometry is completely established throughout the country through aquifer mapping.