having not looked into it at all: it probably doesn't "need" to be fresh water, but it'll probably be rivers anyways.

i assume it works similarly to other large scale cooling operations: you have a closed loop for the heat exchangers and the cooling towers are fed by a local source of flowing water.

doesn't need to be all that clean, or fresh water, but since rivers are pretty much the only source of moving water in most places, there's not really many other options. (for the cooling towers, not AI datacanters...they could just NOT build them, if they weren't fuckwits)

same as nuclear power plants, or any other industrial application that needs a lot of cooling!