This Is How Much Groundwater Earth Has Left
Finding water on other planets, particularly on Mars, might be an exciting discovery and might give some hope for the future of mankind. But that perhaps shouldn't distract us from the real problem at hand: our own depleting water resources. Groundwater, in particular, is the most commonly used manifestation of water on the planet. As such, it is also the most exploited and most often taken for granted. A group of scientists from different universities published on Nature Geoscience the findings of the first data-driven survey of the earth's groundwater supply. And the results are a bit worrying.
More than just an analysis of how much groundwater there is, something that hasn't exactly been done using gathered data, the study also tries to determine the "age" of the water, how old or young it is in relation to other groundwater. This factor is important in determining how renewable that kind of groundwater is. Older groundwater is found deeper, sometimes saltier than even seawater, and might contain traces of arsenic or uranium. They are also practically non-renewable.
Of the 23 million cubic kilometers of groundwater surveyed from multiple datasets, scientists have estimated 0.35 million cubic kilometers is only less than 50 years old. The implication is that we are consuming more groundwater than we can replace within the span of a human lifetime. As more "modern" groundwater is more vulnerable to climate change because it is closer to the surface, this will eventually lead to some rather substantial changes in the near future.
The scientists findings about the volume of groundwater per specific areas more or less match what intuition might tell us. The largest deposits can be found in the Amazon Basin, the Congo, and Indonesia, just to name a few. The least amount are, of course, in more arid places like the Sahara. The dataset doesn't include high northern latitude areas because how satellites are unable to cover these ranges, but they are presumed to have very little groundwater because they are mostly under permafrost.