Entire country has been classified into 14 Principal Aquifer Systems and 42 major aquifersbased on the hydrogeological characteristics. Alluviums covers maximum area of around 31% of the entire country and available in Uttar Pradesh, Bihar, West Bengal, Assam, Odisha and Rajasthan. Around 20% of the area of the country is covered by Banded Gneissic Complex (BGC) and Gneiss aquifers which are available almost in all the peninsular states as well as the Himalayan states.Basalt aquifer covers around 17% area of the country and mainly spread over Maharashtra, Madhya Pradesh, Gujarat, Rajasthan and Karnataka. Sandstone aquifer covers around 8% area in the country and available in Chhattisgarh, Andhra Pradesh, Madhya Pradesh, Gujarat, Karnataka and Rajasthan.Shale aquifer accounts for around 7% of area andLimestone aquifer covers a very small area of around 2% in the country.The rest 15% of the entire area is covered by aquifers namely; Schist, Granite, Quartzite, Charnockite, Khondalite, Laterites and Intrusive.