More than half of south Asia's groundwater too contaminated to use – study
Sixty per cent of the
groundwater in a river basin supporting more than 750 million people in
Pakistan, India, Nepal and Bangladesh is not
drinkable or usable for irrigation, researchers have said.
The biggest threat to
groundwater in the Indo-Gangetic Basin, named after the Indus and Ganges
rivers, is not depletion but contamination, they reported in the journal Nature
Geoscience.
“The two main concerns
are salinity and arsenic,” the authors of the study wrote. Up to a depth of 200m
(650ft), some 23% of the groundwater stored in the basin is too salty, and
about 37% “is affected by arsenic at toxic concentrations”, they said. The Indo-Gangetic
basin 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.
Fifteen
to twenty million wells extract water from the basin every year amid
growing concerns about depletion. The new study – based
on local records of groundwater levels and quality from 2000 to 2012 – found
that the water table was in fact stable or rising across about 70% of the
aquifer.
It was found to be
falling in the other 30%, mainly near highly populated areas.
Groundwater can become
salty through natural and manmade causes, including inefficient farmland
irrigation and poor drainage. 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.
