Billions of people depend on vast subterranean reservoirs of groundwater for daily activities. Increasing depletion of global groundwater supply poses a potential threat to what is still a largely global agricultural system, according to Marc Bierkens of Utrecht University in the Netherlands who led the study.
“If you let the population grow by extending the irrigated areas using groundwater that is not being recharged, then you will run into a wall at a certain point in time, and you will have hunger and social unrest to grow with it,” he cautioned.
The scientists compared estimates of groundwater added by rain and other sources to the amounts used for agriculture and irrigation. They also constructed models to estimate the rates at which groundwater is both added to aquifers and withdrawn.
The team discovered that the rate at which global groundwater stocks are shrinking has more than doubled between 1960 and 2000, rising to 283 cubic kilometers lost annually from 126 cubic meters.
Through evaporation and precipitation, groundwater depletion contributes 0.8 millimeters annually to the sea level rise, about a quarter of the current total rate of 3.1 millimeters per year.
The highest rates of groundwater depletion occur in some of the world’s major agricultural centers, including northwest India, northeastern China, northeast Pakistan, California’s Central Valley and the Midwestern United States.
Groundwater represents about 30 percent of the available freshwater on the planet, while the rest is locked up in glaciers or polar ice caps. Thus, any reduction of the availability of groundwater supplies could have extreme effects for a growing human population.
