You make a point; data centers are indeed boiling away fresh water reserves. But you're also asking what the direct source of pollution is, in order to more effectively argue against the data centers

Because these data centers require energy and cooling, while also working with "razor-thin margins" of AI competition... they are reinvigorating coal and fossil fuels, through use of an existent infrastructure

But also, nobody asked for them to dump billions into this... though dumping the same amount of effort and capital into renewable energy (as well as curbing climate disaster), isn't apparently as readily profitable

It's hard to directly blame "increased pollution" on data centers, because that would be silly to allow such linear blame to be seen, in all the grift. And could also decrease overall profitability if the general public made the connection

The pollution comes from their use of existing infrastructure, while doubly, they could be building renewable infrastructure. It's just not profitable in such a corporate world to do anything but scrape the remnants of a dying world

Edit: Don't forget to recycle!