Groundwater depletion will soon be as important a factor in contributing to sea-level rise as the melting of glaciers other than those in Greenland and Antarctica, scientists say.
That’s because water pumped out of the ground for irrigation, industrial uses, and even drinking must go somewhere after it’s used—and, whether it runs directly into streams and rivers or evaporates and falls elsewhere as rain, one likely place for it to end up is the ocean.
To find out how much of an effect this has on sea level, a team of Dutch scientists led by hydrologist Yoshihide Wada, a Ph.D. researcher at Utrecht University, divided the Earth’s land surface into 31-by-31-mile (50-by-50 kilometer) squares on a grid to calculate present and future groundwater usage.
To make the calculation as precise as possible, they used not only current groundwater-use statistics from each country, but also economic growth and development projections. They also took into account the impact of climate change on regional water needs, considering “all the major factors that contribute,” Wada said.
Because aquifers can be refilled, the scientists also used climate, rainfall, and hydrological models to calculate the rate of groundwater recharge for each region. From this, they projected the net rate of groundwater depletion.