Transboundary groundwater of the Ganges–Brahmaputra–Meghna River delta system

Abstract The Ganga–Brahmaputra–Meghna (GBM) River delta is the world’s largest fluvio–deltaic system and hosts one of the most prolific transboundary aquifer systems of the world that is shared between India and Bangladesh. Since the major shift from surface water usage in the 1970s, the groundwater from these aquifers serves as the primary source of drinking and irrigation water for more than 150 million people residing within the delta. While large-scale usage of groundwater has reduced the prevalent cases of water-borne diseases such as diarrhea and has ensured better food security, it has also exposed millions of people to the widespread occurrence of toxic levels of arsenic (As) in the groundwater of the delta, resulting in the largest mass poisoning in history. Also, the human-induced stress caused by heavy exploitation of the groundwater across the delta is found to disturb the natural flow system of the aquifer, accompanied by a steady decline in the hydraulic head in some areas, especially around the metropolitan centers. Over the years, persistent efforts have been made by both governmental and non-governmental organizations to mitigate groundwater As contamination, using technologies such as removal filters and surface water treatment (as an alternative freshwater source), along with identification and installation of As-free tube wells. However, these mitigation measures are yet to successfully reach the entire As-affected population residing within the delta, and millions of people remain exposed to severe As toxicity in their drinking water and food.