An international team of hydrologists has unveiled that around six quintillion gallons of groundwater is present in earth. The study provides the first data-driven estimate about the amount of water present in earth’s soil, sand and aquifers.

Earlier estimates about the groundwater level were based on crude estimates carried out in the 1970s. Tom Gleeson of the University of Victoria said, “We already know that water levels in lots of aquifers are dropping. We’re using our groundwater resources too fast – faster than they’re being renewed”.

The researchers have also come to know about how old groundwater is. They have found that the top section of groundwater known as modern is less than 50 years old. To know the planet’s total volume of modern groundwater, the researchers measured global levels of tritium, a radioactive isotope of hydrogen fused into groundwater.

From 55 nations, the researchers took 3,700 tritium measurements. Study’s co-author Elco Luijendijk from Göttingen University’s Geoscience Centre said, “Although the volume of modern groundwater may appear small at first glance, it is still much larger than all other components of the active hydrological cycle such as water in rivers, lakes, and the atmosphere”.

In comparison to older groundwater, it is more important to know about the volume of modern groundwater as it is more renewable. It shall also be noted that modern groundwater is also vulnerable to climate change.