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Comment by carefree-bob | Hacker News Reader

Most data centers are closed loop systems, they circulate the water over and over again.

You understand, the water isn't used up? It's not even used up in agriculture. Even when you drink a glass of water, the water doesn't actually disappear, soon someone else will be drinking it. The same water that was on the earth when the dinosaurs walked the planet is still on the earth today. No need to panic about someone using water.

The only reason to be concerned is if someone is mixing the water with other chemicals at a rate faster than the natural filtration and then not paying for the treatment to purify the water again. But that is not an issue with data centers. Merely using water is a concern only for people who don't understand how matter is preserved, but a school physics book should dispel those concerns.

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Sure the water is still somewhere, but its location is important for future use. US water reservoirs are at problematically low levels already.

> Most data centers are closed loop systems, they circulate the water over and over again.

The linked article talks about >500 million gallons used by one large Google AI datacenter in a year. It's nice that most are closed loop systems, but if it's such a common thing to do then why isn't it done by default with all those AI datacenters? How cheap is water for Google that recirculating it is not a no-brainer?

"Recirculating" water isn't thermodynamically the same. Evaporating the water is THE POINT of the system. You can make closed-loop coolers but they use more energy.

Which makes the often repeated excuse "Closed loop datacenters exist" to refute water use concerns a bit nonsensical.

It's all contextual. If the energy inputs are carbon-free and local water is scarce, then for that given situation a closed-loop system might make sense. People are building such a thing in Tucson, Arizona right now.

> It's not even used up in agriculture.

However, the source of the water can be "used up" faster than it can be replenished, such as in the case of some aquifers

That’s not entirely correct. Overall water is preserved but local sources of freshwater can be depleted or contaminated, which raises the cost of water.

> The same water that was on the earth when the dinosaurs walked the planet is still on the earth today.

Nope. Plants turn water into oxygen and (the H part of) hydrocarbons, and animals turn those back into water. And after that, the result is different water than the cycle started with.

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