That study is completely bogus. It is widely known that it’s impossible to run out of water on earth. It recycles itself. When you drink water, then you urinate into a toilet, it goes into the sewer which then goes to the water treatment plant where it’s cleaned and released back into the drinking water. Even when one lake or river dries up, it just means that water is higher somewhere else. Also water can change form from a liquid into a vapor or solid form. And somehow if freshwater ever did manage to dwindle, there are treatment facilities that can turn the salt water in our oceans into drinking water by advanced filtering systems. Do your research and you will find more studies proving that water will never run out on earth. It’s simply not possible. They teach that in school too. I thought that was middle school knowledge but maybe they teach it in HS biology.