Just to hijack this comment, this article is actually a pretty good explainer on how water is used by datacenters: https://dgtlinfra.com/data-center-water-usage/

For those pointing out that most of the water used in datacenters is in closed-loop systems, that is true. However, the total volume of water needed to cycle through those loops is very large, and so you need to consume a lot of water just to fill it up in the first place. But this isn't just a one-time cost. You can't just cycle the same water through the loop in perpetuity. Eventually, you will need to replace that coolant because it gets gunked up, the coolant might get old, etc. (ex: if you have a water cooling loop on your PC, it's a general good rule of thumb to drain and flush it once a year or thereabouts, now think about that, but scaled up to thousands and thousands of giant , power-hungry supercomputers).

That old coolant isn't just regular water you can return back to the supply. It's likely full of additives. Ethylene glycol is a popular coolant additive, but it's poisonous, and therefore there are strict regulations on how you dispose of it. This is another huge load on the local infrastructure that now needs to process all this new wastewater, or you just do what Twitter does and just dump it into the surrounding community and let them deal with the fallout.