April 22 (UPI) -- If groundwater levels continue to decline as they have over the last several decades, new research suggests approximately one-fifth of groundwater wells around the world will be at risk of running dry.
Groundwater wells are the main source of water for roughly half the globe's population, but over the last half-century, many of the planet's major aquifers have suffered from mismanagement, growing human pressures and prolonged droughts.
The latest analysis, published Thursday in the journal Science, suggests millions of wells could run dry if aquifers continue to be depleted and regional water tables keep declining.
"Groundwater is a reliable, perennial source of water," study co-author Debra Perrone, an environmental scientist and assistant professor at the University of California, Santa Barbara, told UPI in an email.
"In many places, groundwater does not require treatment for drinking water purposes, making groundwater a strategic resource for meeting sustainable development goals and adapting to impacts from a changing climate," Perrone said.
Despite its importance, few studies have taken global view of groundwater wells and their vulnerability to aquifer depletion.
To do just that, Perrone and research partner Scott Jasechko compiled data on millions of wells from all over the world.
"We compiled 134 different well completion databases to map groundwater well locations and depths in 40 countries around the globe," Jasechko, an assistant professor of water resources at UCSB, told UPI in an email.
The data showed between 6% and 20% of wells around the world are no more than 16 feet below the local water tables.
If aquifers continue to decline at current rates, many of those wells could begin to run dry in the decades ahead.
"Before these maps, most of our understanding of where groundwater wells were located was based on local-to-regional information or, at larger-scales, anecdotal information," Perrone said.
"These maps show, for the first time, local information stitched together to get a global perspective of groundwater use," Perrone said.
The study's co-authors said local data is essential to managing groundwater resources and informing well construction. But because aquifers span political borders and can be affected by disparate variables, global surveys can provide important insights.
"A global perspective is fundamental to inform broader sustainability goals," Perrone said. "What is unique about our analysis is that we assess groundwater depth trends using local information at a global scale."
The researchers said they hope their latest survey will draw attention to the importance of groundwater as a global resource -- one that remains vulnerable to climate change and human development.