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.

The classification of India's aquifer systems into 14 principal and 42 major aquifers reflects the country's vast and varied hydrogeological landscape. Alluvial aquifers, covering the largest portion of the nation, are predominantly found in the Indo-Gangetic plains and parts of Rajasthan, supporting intensive agriculture and dense populations. These formations consist of unconsolidated sediments deposited by major river systems, offering substantial groundwater storage and yield potential. Understanding the distribution and characteristics of these aquifer systems is fundamental to the NAQUIM mission, enabling targeted management strategies that balance extraction with natural recharge across different geological terrains.

The Banded Gneissic Complex and Gneiss aquifers form the second most extensive groundwater-bearing formation in India, spanning peninsular and Himalayan states alike. These hard-rock aquifers present unique challenges for groundwater management due to their limited primary porosity and dependence on secondary fractures and weathering zones for storage. Despite covering roughly a fifth of the country's area, their groundwater potential varies significantly based on local structural geology and depth of weathering. The NAQUIM project emphasizes detailed aquifer mapping in these regions to identify sustainable yield zones and guide community-led recharge efforts.

Basalt aquifers, primarily associated with the Deccan Traps, dominate the hydrogeology of central and western India, covering approximately seventeen percent of the national landmass. These volcanic formations exhibit layered sequences where groundwater movement is controlled by cooling joints, fractures, and vesicular zones between massive basalt flows. The heterogeneity of basalt aquifers makes their assessment particularly complex, requiring integrated geological and geophysical investigations. Through systematic aquifer mapping under the NAQUIM framework, authorities aim to delineate productive zones within these challenging formations and implement site-specific management plans that enhance groundwater security.

Beyond the major aquifer classifications, India's groundwater framework includes diverse systems such as sandstone, limestone, and crystalline aquifers found across various states. Each aquifer type responds differently to seasonal recharge, abstraction patterns, and climatic variability, necessitating region-specific evaluation methodologies. The NAQUIM initiative recognizes this diversity by employing a multi-disciplinary approach that combines remote sensing, geophysical surveys, and hydrochemical analysis. This comprehensive understanding supports the development of aquifer management plans that address both quantity and quality concerns, ensuring long-term sustainability of groundwater resources for drinking, irrigation, and industrial uses across the country.