While the findings may look worrisome, scientists said that there is also a piece of good news – the amount of groundwater that can be replenished is three times larger than any other source of fresh water such as rivers and lakes on Earth.
Nevertheless, there are concerns that the slow pace groundwater gets replenished at may cause the resource to run out. This may challenge the commonly held belief that the supply of groundwater gets automatically replenished by rainfall and melting snow just like lakes are. Yet, few people know that underground reservoirs of fresh water are replenished much more slowly.
Tom Gleeson, co-author of the study and hydrogeology expert at University of Victoria in British Columbia, Canada, explained that just 6% of groundwater is renewed within a ‘human lifetime.’
Since groundwater is located a few hundred feet of the surface, there is also the risk of pollution, and evaporation because of high temperatures at ground level. Also, diminished rainfall and shrinking snowpacks may affect the rate at which the resource gets renewed.
In a recent interview, Gleeson underscored the importance of groundwater. He noted that nearly 3 billion people worldwide rely on the resource every day for drinking and economic activities that allow them to survive.
Because of its importance, groundwater stirred up the interest of researchers at several universities including University of Texas at Austin, University Gottingen in Germany, and University of Calgary in Alberta, Canada. The team planned to learn just how much groundwater was left and how fast it replenished.
Other studies have tried to map underground sources of fresh water, as well, but none of them was able to estimate the rate these resources were replenished at. Gleeson’s team, however, found a method of detecting which groundwater was not yet 50 years old.
During the Cold War, the world’s most powerful nations conducted above-ground nuclear tests. This is how a radioactive element dubbed tritium made it to the planet’s supply of fresh water.
The research team concluded that groundwater with high amounts of tritium was replenished since the 1960s, when the nuclear tests were conducted, while water with no tritium was older.
Researchers based their analysis on 3,500 measurements of tritium levels in nearly 60 states. They also used computer simulations to learn how groundwater was flowing around the world and how old it was.
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