The Indus Basin aquifer shared by Northwestern India and Pakistan is the second-most “overstressed” underground water reserve, two new studies have found, as human activity rapidly drains about one-third of the world’s largest aquifers.
The researchers said the Arabian Aquifer System, which provides water for more than 60 million people, is the world's most overstressed source. The Indus Basin aquifer was second and the Murzuk-Djado Basin in northern Africa third, they said.
The Indus Basin represents an extensive groundwater aquifer, covering an area of 16.2 million hectares and the aquifer was in a state of hydrological equilibrium before the development of a canal irrigation system by India and Pakistan, according to a 2011 report of the Food and Agriculture Organisation.
"What happens when a highly stressed aquifer is located in a region with socioeconomic or political tensions that can't supplement declining water supplies fast enough?" said Alexandra Richey, the lead author for the new studies.
"We're trying to raise red flags now to pinpoint where active management today could protect future lives and livelihoods."
It is unclear how much water remains in underground reserves and huge sections of the population are using up groundwater without knowing when it will run out, researchers said in findings published in the journal Water Resources Research.
Scientists used data from special NASA satellites to measure groundwater losses.
In one paper, they looked at 37 of the world’s biggest aquifers between 2003 and 2013. Eight of these were classified as "overstressed", meaning they were being sucked dry with almost no natural replenishment to offset usage.
Five other aquifers, including the Indus Basin aquifer, were classified as "extremely or highly stressed."
The US government has already identified water stress as a potential driver of regional insecurity that can contribute to regional unrest.
South Asia’s three major river systems – the Indus, Ganges and Brahmaputra – sustain India and Pakistan's breadbasket areas and many of their major cities including New Delhi and Islamabad, as well as Bangladesh.
The strain on groundwater in India is most disturbing. More than 60% of irrigated agriculture and 85 percent of drinking water in the country depend on it, says the World Bank. Yet in 20 years, most of its aquifers will be in a critical condition.
“Given how quickly we are consuming the world's groundwater reserves, we need a coordinated global effort to determine how much is left," said University of California Irvine professor Jay Famiglietti, the principal investigator in the new studies.
The scientists warned the situation will worsen with climate change and population growth. The most overburdened aquifers are in the world's driest places, where there is little natural replenishment.
The second paper concluded that the total remaining volume of the world's usable groundwater is poorly known and huge discrepancies exist in estimated "time to depletion".
"We don't actually know how much is stored in each of these aquifers. Estimates of remaining storage might vary from decades to millennia," Richey said.
"In a water-scarce society, we can no longer tolerate this level of uncertainty, especially since groundwater is disappearing so rapidly."