Oh boy, here we go again. We had this discussion two weeks ago over on !conservation@slrpnk.net (with a cross-post to a vegan community, but please don't go there and start harassing vegans. It was enough of a shit-show already.), where I wrote way too long of a comment, and the post got deleted afterwards. What a waste. But since it is brought up here again, I'm gonna recycle some of that and make you relive it with me. [Turns out this comment is even longer than my original one. Sorry for that.]

The best source I could find to get a rough idea of what is using how much water (in the USA) was the USGS Estimated Use of Water in the United States in 2015. (yes, there were no AI data centres in 2015, but bear with me, this is gonna be a long ride.)

One of the main problems in discussing this is that there are different kinds of water use, which luckily the USGS publication differentiates - namely "consumptive use" (water that is not available after the process) and, well, "non-consumptive use" (they report it as "reclaimed waste-water", i.e. water that, possibly after treatment, is immediately returned to rivers or similar for further use).

As the report compares total water use, "thermoelectric" (not sure why they use that term, it's probably supposed to be "thermal") power generation is the biggest reported category with 41%, followed by irrigation with 37%. When looking at consumptive use, the share is vastly different - only a fraction of the water used by thermal power generation is evaporated (see page 42), it consumes "only" 4.3 BGal/day, compared to 73 BGal/day for irrigation (page 30). That's not even in the same ballpark!

Turns out water use != water use. However I’d argue, that people would rather agree, that the kind of water “consumed” by growing plants is more permanent than water being “consumed” by cooling power plants, where most of the water is put back into the water cycle immediately.

So now we have a rough picture of how much water is used for agriculture, and how much for (thermal) power generation.

My point would be that it is very unlikely, that AI data centres use more water than the power plants that generate their electricity (on average; not all electricity is generated in thermal power plants), especially as thermal power plants generate at least as much heat as electricity, so the power plants already need as much cooling as you'd need if you just turned their electricity into heat (which data centres basically do). But even if the data centres used as much water as all the thermal power plants in the USA, it would still only be a fraction of the water used for irrigation.

Now considering that feeding animals is less efficient in converting farmed area and water to calories for human consumption instead of directly feeding people, and it should be quite obvious, that animal products are responsible for a big portion of easily avoidable water usage (For some fun comparisons: calorie supply by food group - In the USA 72% of calories are provided by plants, the remaining 28% are some form of animal product vs global land use for food production - 80% of agricultural land is estimated to be for livestock, vs 16% for food crops (granted, livestock land includes land for grazing, but even without that, it's 6 million km^2 for animal feed crops vs 8 million km^2 for crops for human food, so disproportionate to the amount of calories they provide))

And on top of all of that, if it wasn't already enough - the water usage of animal agriculture hasn't just recently started to become a problem, it has been a problem for quite some time. In the USA most aquifers are drying up including some very important ones for agriculture - and that was a problem before AI data centres sprung up everywhere

Water consumption of AI is not the main environmental problem, its energy use and especially the source of that energy is way more concerning.

The thing is that yes, we should not use AI for all the reasons that have been mentioned numerous times, but if you focus on environmental problems, then the best thing you can do is stop eating animal products. Heck, it doesn't even cost anything. On the contrary, it would be cheaper. It doesn't even require new technologies! Going vegan is degrowth in action.

That being said, I'll still condemn you if you use AI, even if you are vegan.