India's groundwater reserves at depletion risk: study

Excessive pumping of water for drinking and agriculture could deplete groundwater resources in parts of India, southern Europe and the US in the coming decades, a new research has warned.
New modelling of the world's groundwater levels found that aquifers - the soil or porous rocks that hold groundwater - in the Upper Ganges Basin area of India, southern Spain and Italy could be depleted between 2040 and 2060.
In the US, aquifers in California's Central Valley, Tulare Basin and southern San Joaquin Valley, could be depleted within the 2030s, researchers said.
Aquifers in the southern High Plains, which supply groundwater to parts of Texas, Oklahoma and New Mexico, could reach their limits between the 2050s and 2070s, they said.

By 2050, as many as 1.8 billion people could live in areas where groundwater levels are fully or nearly depleted because of excessive pumping of groundwater for drinking and agriculture, according to Inge de Graaf, a hydrologist at the Colorado School of Mines in Colorado, US.
"While many aquifers remain productive, economically exploitable groundwater is already unattainable or will become so in the near future, especially in intensively irrigated areas in the drier regions of the world," said de Graaf.

Knowing the limits of groundwater resources is imperative, as billions of gallons of groundwater are used daily for agriculture and drinking water worldwide, said de Graaf, who presented the findings at the fall meeting of the American Geophysical Union in San Francisco.

Previous studies used satellite data to show that several of the world's largest aquifers were nearing depletion. But this method can not be used to measure aquifer depletion on a smaller, regional scale, according to de Graaf.
In the new research, de Graaf and colleagues from Utrecht University in the Netherlands used new data on aquifer structure, water withdrawals and interactions between groundwater and surrounding water to simulate groundwater depletion and recovery on a regional scale.
The research team used their model to forecast when and where aquifers around the world may reach their limits, or when water levels drop below the reach of modern pumps.

Limits were considered "exceeded" when groundwater levels dropped below the pumping threshold for two consecutive years.
The new study finds heavily irrigated regions in drier climates, such as the US High Plains, the Indus and Ganges basins, and portions of Argentina and Australia, face the greatest threat of depletion.
Although the new study estimates the limits of global groundwater on a regional scale, scientists still lack complete data about aquifer structure and storage capacity to say exactly how much groundwater remains in individual aquifers, researchers said.
"We don't know how much water there is, how fast we are depleting aquifers, or how long we can use this resource before devastating effects take place, like drying up of wells or rivers," de Graaf said.