Human life is directly linked to water. We can last only three days without drinking it, but we pretty much take it for granted. Maybe we shouldn’t.

According to a new study, access to water will soon get much harder because of climate change, and arid areas in the US will expand.

A large part of the people living on the planet relies on groundwater, which is basically water stored in underground deposits called aquifers. Some of these aquifers, however, are close to the surface — making them vulnerable drought and other climate-change-related phenomena.

A study, published in the journal Nature Communications, showed that the US is set to be affected by a significant loss of groundwater because of climate change, which could mean losing 119 million cubic meters under the most modest scenarios of global warming.

The growing temperatures can alter the supply and demand balance of water. Aquifers can help with the water stress but not forever and only when there’s a connection with shallow groundwater. Not stopping the global warming could deplete the aquifers, researchers argued.

Countries agreed to limit global warming to 2ºC or ideally 1.5ºC under the Paris Agreement on climate change, signed in 2015. Nevertheless, they haven’t shown a sufficient level of ambition to accomplish that goal yet. With the current climate plans, global warming is expected to reach at least 3ºC. This could spell disaster for water management in many parts of the world.

“Even with a 1.5 degrees Celsius warming case, we’re likely to lose a lot of groundwater,” said Reed Maxwell, professor of hydrology at the Colorado School of Mines, who co-authored the paper. “The East Coast could start looking like the West Coast from a water standpoint. That’s going to be a real challenge.”

Maxwell, working with Laura Condon of the University of Arizona and Adam Atchley of Los Alamos National Laboratory, simulated the movement of water in the subsurface and the way it connects with the land surface – an innovative approach compared to previous studies.

The study proved there’s a direct connection between warmer temperatures and groundwater, affecting its storage and evapotranspiration even with a low to moderate global warming. In the western US, these effects may not be noticed for a while, as groundwater is deep and lower levels wouldn’t affect the surface waters.

Nevertheless, the situation is different in the eastern US, the researchers argued, claiming the region will be more sensitive to any changes. Changes in the groundwater would mean negative effects on vegetation and rivers. The region also lacks systems to manage water shortage, which is available in the western part of the country.

“Initially, plants might not be experiencing stress because they still have existing shallow groundwater available, but as we continue to have warmer conditions, they can compensate less and less, and changes are more dramatic each year,” Condon said. “In other words, shallow groundwater is buffering the response to warming, but when it’s depleted, it can’t do that anymore.”

In their study, the researchers didn’t change precipitation patterns and increased temperatures in a range from 1.5ºC to 4ºC. While modest warming of 1.5º would mean losing 119 million cubic meters of water storage, a 4ºC would mean losing 324 million cubic meters.