Hydrogeological typologies of the Indo-Gangetic basin alluvial aquifer, South Asia

The Indo-Gangetic aquifer is one of the world’s most important transboundary water resources, and the most heavily exploited aquifer in the world. Here we characterise typologies for the aquifer which integrate existing datasets at a transboundary scale for the first time, and provide a new lens through which to view this aquifer system. Traditionally considered and mapped as a single homogenous aquifer of comparable aquifer properties and groundwater resource at a basin-scale, the typologies illuminate significant spatial differences in recharge, permeability, storage, and groundwater chemistry across the aquifer system at a basin-scale. These changes are shown to be systematic, concurrent with large-scale changes in sedimentology of the Pleistocene and Holocene alluvial aquifer, climate, and recent irrigation practices. We present seven typologies of the aquifer each having a distinct set of challenges and opportunities for groundwater development and a different resilience to abstraction and climate change. The seven typologies are: 1. The piedmont margin; 2. The Upper Indus and Upper-Mid Ganges; 3. The lower Ganges and Mid Brahmaputra 4, The fluvially-influenced deltaic area of the Bengal Basin; 5. The Middle Indus and Upper Ganges; 6. The Lower Indus; and 7. The Marine influenced deltaic areas.