Kathmandu, August 30
More than half of the groundwater in south Asia’s most important river basin where more than 750 million people live, is not drinkable or usable for irrigation, researchers say.
The biggest threat to groundwater in the Indo-Gangetic Basin, which spans Pakistan, India, Nepal and Bangladesh is not depletion, as is popularly believed, but it is contamination, a report in the journal Nature Geoscience says.
The main causes of contamination, according to the report, are salinity and arsenic.
Up to a depth of 200 metres (650 feet), some 23 percent of the groundwater stored in the basin is too salty, and about 37 percent “is affected by arsenic at toxic concentrations,” they say.
The Indo-Gangetic basin, named after the Indus and Ganges rivers, accounts for about a quarter of the global extraction of groundwater — freshwater which is stored underground in crevices and spaces in soil or rock, fed by rivers and rainfall.
According to the study, 15-20 million wells extract water from the basin every year as concerns about depletion looms.
The study, however, found that the water table was in fact stable or rising across about 70 percent of the aquifer between 2000 to 2012.
According to the report manmade, as well as natural causes were responsible for the contamination. Inefficient farmland irrigation and poor drainage are the two manmade reasons, the report notes. Arsenic, too, is naturally present, but levels are exacerbated by use of fertilisers and mining. Arsenic poisoning of drinking water is a major problem in the region, it says.
