I don't know the answers to a lot of these questions, I assume they heat up the water, and dump it back into the rivers, which causes some disruption to the local ecosystem. Which is fine if you do it in small amounts, but it will disrupt things. (powerplants have the problem for example that some flora/fauna gets attracted to these more warmer waters, risking clogs and more. (so a datacenter does this twice, first via the powerplant generating power, and then to cool the datacenter).

There is also the issue of contamination, while I assume they don't put extra dirty things in the water, this is not a guarantee, nor will every municipality/gov just go with the assumption that it is clean, I assume that in some places this cooling water will need to be cleaned extra as industrial waste. Esp when there are some odd laws interacting. (I know some of those laws re waste and what counts as waste interact weirdly in .nl causing weird busywork during roadwork so they don't run into extra costs by accidentally letting the waste count as a different class of waste).

But yes, I think they do not recirculate, and just pump it round and dump it back into the river directly (so no evaporative cooling where the water goes into the air, which you had at some powerplants, the big towers), and I assume they don't use lead pipes so the water isn't very contaminated. But these sort of processes do put a strain on the water quality. (In .nl we have some problems with river water quality because our big rivers come from industrial areas of other countries, (Germany mainly)).

I mostly posted it so that we now at least have some indication of the amounts we are talking about, as tech companies are very tight lipped about this. But as somebody who knows nothing, I do not know all the implications of it. I am however suspicious, due to a combination of natural paranoia, them being very mum about it, and me not trusting the big tech places.

But yeah, if they use up 90% of the daily flow of a river and heat it up, that will absolutely not be good for the local ecosystem. And any industrial site downstream who also wanted to use the water for cooling now also in trouble.

Bit like the same reason I posted about protonmail, more an FYI than a sneer (not a huge shock that eventually protonmail would reveal the data if forced by their gov, they always said they would do this, but it is an important thing to take into account if you worry about privacy).