If you are working outdoors in hot weather (35°+) you can easily require 8-10L of water a day. That's like 50 "glasses". Then the next day if it's 20° you'll need only a handful of liters. It all depends on context. The article makes a great point that humans are super water inefficient. But we can handle high heat and aerobic output so long as we have water.

The article is there.

> if you were to ask someone why you need to drink this much water every day, they probably wouldn’t be able to tell you.

I suspect that the bottled water producers could tell us a bit, especially their marketing divisions.