In early November, The New York Times ran the following headline: “America is depleting groundwater like there’s no tomorrow.” Journalists of a well-known publication published a study on the state of groundwater reserves in the United States. They concluded that the United States was pumping too much groundwater.

However, the USA is not an isolated example. “The rest of the world is also wasting groundwater like there is no tomorrow,” says Hansjorg Seybold, senior researcher at the Department of Environmental Systems Science at ETH Zurich. He is a co-author of the study newly published in the journal. Nature.

Scientific evidence that water resources are rapidly depleting

He confirmed the journalists’ alarming results together with researchers from the University of California at Santa Barbara (UCSB). A lot of groundwater is pumped out not only in North America, but also in other parts of the world where people have settled. In an unprecedentedly rigorous study, researchers collected and analyzed data from more than 170,000 groundwater monitoring wells and 1,700 groundwater systems over the past 40 years.

These measurements show that humans have greatly increased groundwater extraction worldwide in recent decades. Water levels in most rock layers that contain groundwater, known as aquifers, have fallen dramatically in almost every part of the world since 1980. Since 2000, this decrease in groundwater reserves has accelerated. The effects are most pronounced in aquifers in arid regions of the world, such as California, the High Plains of the United States, Spain, Iran, and Australia.

“We weren’t surprised that groundwater levels were dropping dramatically around the world, but we were shocked to see how quickly that rate has increased over the last two decades,” says Seybold.

One of the reasons for the rapid decline in groundwater levels in arid regions, Seybold says, is that humans use these areas extensively for agriculture and pump (too) much groundwater to the surface to irrigate plants, as in California’s Central Valley.

Rising food supply and climate change are making the problem worse

Additionally, the world population is increasing, which means more food needs to be produced in the arid regions of Iran, for example. It is one of the countries where underground water resources are decreasing the most.

But climate change is also exacerbating the groundwater crisis: In recent years, some areas have become drier and hotter, meaning crops need more irrigation. In cases where climate change causes precipitation to decrease, groundwater resources recover more slowly.

Heavy rains, which are becoming more frequent in some places due to climate change, do not help either. If water comes in large quantities, the soil often cannot absorb it. Instead, water flows to the surface without seeping into groundwater. This problem is especially acute in places with high levels of soil compaction, for example in large cities.

The trend may be reversed

“The study also reveals some good news,” says co-author Debra Perrone. “Aquifers have recovered in some areas where policy changes have occurred or alternative water sources are available for direct use or aquifer recharge.”

A positive example is the Geneva Aquifer, which provides drinking water to approximately 700,000 people in the canton of Geneva and the neighboring French Haute-Savoie region. The level fell sharply between the 1960s and 1970s due to uncoordinated pumping of water by both Switzerland and France. Some wells even ran dry and had to be closed.

In order to preserve the common water resource, politicians and officials of both countries agreed to artificially recharge the aquifer with water from the Arve River. Initially, the plan was to stabilize the groundwater level, then raise it, and the intervention was successful. “Although the water table in this aquifer has not yet returned to its original level, this example shows that groundwater levels do not always have to go in one direction, that is, downwards,” says Seybold.

Other countries are also responding

Authorities had to take action elsewhere, too: In Spain, a major pipeline was built to transport water from the Pyrenees to central Spain, which feeds the Los Arenales groundwater. In Arizona, water is diverted from the Colorado River to other bodies of water to replenish groundwater reserves, but this causes the Colorado River Delta to dry out at times.

“These examples are a glimmer of hope,” says UCSB researcher and lead author Scott Jasiechko. Still, he and his colleagues are calling for more action to combat groundwater depletion. “After significant depletion of groundwater resources in semi-deserts and deserts, it can take hundreds of years to recover because there is not enough rainfall to quickly replenish these groundwater resources,” says Jasechko.

There is an additional danger on the coast: If the groundwater level drops below a certain level, seawater can enter the ground. This leads to salinization of wells, making the pumped water unsuitable for drinking and irrigation areas; Trees whose roots reach groundwater flow die. There are already large ghost forests on the east coast of the United States where there is not a single living tree.

“That’s why we can’t put the problem on the backburner,” says Seibold. “The world must act urgently”