Quality not quantity greatest threat to key groundwater source

The greatest threat to sustainable groundwater in the Indo-Gangetic Basin is contamination and not depletion, according to a study co-authored by UCL researchers and published this week . Using groundwater measurements from across the region, the study reveals that over 60% of accessible groundwater is no longer safe to drink or usable for irrigation due to high concentrations of arsenic or salinity. The Indo-Gangetic Basin is the drainage area of the Indus, Brahmaputra and Ganges Rivers whose underlying  sediments form the world's most intensively developed groundwater system. This basin alone accounts for a quarter of all groundwater withdrawn globally and supports the livelihoods and agricultural activities of more than 750 million people in Pakistan, India, Nepal and Bangladesh. Most of the groundwater is used to irrigate food crops, such as rice and sugar cane, but it is also used for drinking water - especially for the cities of Delhi, Dhaka and Lahore. The study looked at thousands of groundwater field measurements in combination with existing groundwater datasets to reveal a diverse picture of groundwater changes across the Indo-Gangetic Basin over the past decade. The authors found that groundwater levels are falling in 30% of the basin, particularly near major cities, but are stable or even increasing across the other 70% due to recharge from leaky irrigation canals.