Ok, now I understand, thanks for the crash course on dc cooling!

I assumed scale was my issue but having only second-hand knowledge of coastal larger-scale cooling systems was the big part of my problem. Then I couldn't understand why they were building them inland, especially with the mineralization issue when drawing from inland reservoirs. So I thought that might be a tax jurisdiction reason, plus comparative cost of metal or pump heat exchange setups, especially because Altman said they weren't using evaporative cooling (not that he's a trustworthy source).

But this made it all click:

both of these mean extra capex and/or energy use, but evaporating water is cheap, so it’s done instead. it doesn’t help that one of dc ratings is ratio of how much energy gets into dc to how much energy powers actual silicon.

They were always optimizing for the cost, but I didn't know about this regulation. Water usage is probably either absent from the regulations or a minimal contribution to it, so they've used it as the trade-off without adequate (if any) modeling for impact. They've probably since done a little of that and found it's pretty catastrophic. A little extra reading indicates the 2-8 million gallons is the supply per day by the county, and not total (re)circulating water in the dc, which implies evaporative cooling and aligns with what you're saying about it being the cheapest solution.

Cool, everything is yet again awful, but at least it makes sense on some level. I have been educated, and I again thank you for your effort in that.