Arsenic contamination has affected the groundwater of the Ganges, Indus, and Mekong basins, afflicting millions of people with arsenicosis. In the Ganges basin, 20% of deaths are related to arsenic-contaminated drinking water. Site visitations to andsurveys of surface water resources at the affected sites have identified land use and land cover changes as anthropogenic factors that have contributed to this disaster in the river basins. It was also found that due to the construction of dams and barrages upstream of the affected sites, the downstream water supply has been affected by water piracy and has consequently been reduced drastically to about 60%, with surface water resources, such as distributaries, flood plains, ponds, etc., becoming dry. The source of the arsenic contamination is attributed to alluvium-mixed arsenopyrites that are inactive under water but, as the groundwater table sinks following the continued absence of recharging water, form water-soluble compounds of arsenic after contact with atmospheric oxygen. Every season, the contamination is exacerbated because of the scarcity of fresh recharging water with dissolved oxygen that would help to remove arsenic from the groundwater. This is enhanced further when groundwater is overextracted to meet water needs, which exposes more arsenopyrites to atmospheric oxygen. In addition, the movement of groundwater in different spatial and temporal scales spreads contamination to unaffected areas. To help solve this problem, naturally established virgin stream channels should be preserved, and the demolition of dams and barrages is required to restore depleted channels by redistributing water where it had previously been abundant. Finally, upstream water piracy should be minimized in orderto preserve the downstream ecosystem.
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