[coredog64]

I can understand concerns about moving thousands of acre-feet of water into the desert for cooling, or pumping your aquifer dry for the same thing. But moving water from the Great Lakes a few miles inland? How much water evaporates out of the Great Lakes every day, and what is the percentage increase when used for cooling?

[its_ethan]

I don't recall the exact specifics, but I do remember a while ago there was some outrage that Nestle was bottling some really large sounding amount of water (think ~millions of gallons a day?) from a Great Lake. The math behind how much was being used as a % of lake volume was negligible (it would take ~3,500,000 years to "drain" Michigan at that rate).

In my mind this is partly due to people not understanding large numbers, and also not understanding just how much water is actually in the Great Lakes. It's a huge amount - Lake Michigan has 1,288,000,000,000,000 gallons in it. Every human on earth could use close to 10gal of water per day for the next 50 years before Lake Michigan would be "dry", assuming it was never replenished. And that's just Lake Michigan. (Obviously environmental systems are more complicated than the simple division I did, and individual water usage isn't simply 10gal a day - it's just to demonstrate a point).

Now, someone else pointed out that the tragedy of the commons is a sort of death by a thousand cuts. And if anyone who shows up is allowed to draw millions of gallons a day, that can add up and certainly have negative effects. It's just important to actually understand the scale of the numbers involved, and to not let legitimate environmental concerns be cross-contaminated with just anti-tech-of-the-year sentiment, or political motivations, or whatever else might cloud the waters (pun unintended).

[shagie]

It's which side of the drainage basin is the water moved to? When the water is flushed back into the system, does it drain back into the Great Lakes? or down to the Gulf of Mexico?

On the southern shore of Lake Michigan, that "few miles" changes the watershed that its part of.

https://en.wikipedia.org/wiki/Great_Lakes_Basin ( https://www.erbff.org/wp-content/uploads/2025/10/10.8.25-Gre... for a high resolution map)

As for diversions that go to evaporative cooling, that's a big question for the data center itself and there are many designs. https://www.nrel.gov/computational-science/data-center-cooli... has some cutting edge designs, but they're more expensive to use for pumping waste heat elsewhere.

Sometimes you get data centers that look like https://www.oregonlive.com/silicon-forest/2021/11/the-dalles... ... and that's not a little bit of water there.

While the Great Lakes are coming off of wet years ( https://water.usace.army.mil/office/lre/docs/waterleveldata/... ) that shouldn't be used as long term prediction of what will be available in another 10 years lest it becomes another Colorado river problem. Currently, the water levels for Lake Michigan are lower than average and not predicted to return to average in the model range. https://water.usace.army.mil/office/lre/docs/mboglwl/MBOGLWL... . You'll note that this isn't at the minimums from the 1960s... and the Great Lakes Compact was signed in 2008.

You can search the database for the authorized diversions of the water. https://www.glslcompactcouncil.org/historical-information/ba...

For example, Nine Mile Point - https://www.glslcompactcouncil.org/historical-information/ba...

[sensanaty]

But where do we stop with all of this endless expansion? Do the great lakes have to go through an Aral Sea type of situation before we decide it's time to stop? It's not like these AI ghouls are shy about wanting infinite expansion and an ever-growing number of data centers to feed their word generators, do we really think that if we just let them have the water now they're not going to abuse that and that they won't start draining the lakes for all the water they can manage? I'm not so optimistic, myself.

[beart]

Water levels have been down for years as-is. It may not seem like much now, but I think it's important to avoid a "tragedy of the commons" scenario in the future.