Présentations Colloques

Groundwater is a critical resource for hundreds of millions of people in the Indo-Gangetic Basin (IGB) who rely on it for drinking water, agriculture and industry. Intense exploitation for irrigation and domestic water supply is widespread across the IGB, where deeper (typically 100-200 m below ground level) aquifers are generally considered secure long term sources of drinking water. The water quality at depth is generally of superior quality compared to shallow sources which are affected with a range of issues including arsenic, fluoride, nitrate and pathogens. The security of deep groundwater sources are contingent on a range of factors including regional scale geological controls, local and site scale pumping histories and trajectories as well as site specific borehole design and completion. Chemical properties of groundwater can be used as environmental tracers to provide important insights on its hydrogeochemical evolution, origin and residence time. This paper brings together new environmental tracer data from case studies within sedimentary aquifer systems of the IGB where profiles of groundwater residence time and hydrochemistry have recently been collated. Age tracers and hydrochemical depth profiles are compared from areas with contrasting subsurface lithology and pumping histories. These are used to characterize pumping induced changes in age-depth profiles and water quality and understand the regional scale anisotropy of the IGB aquifer system. This new empirical evidence informs the current dialogue regarding the complexity of the IGB aquifer system and the long term security of deep groundwater resources in this region.