The problem is more one of scale: a million liters of water is less than half of a single Olympic-sized swimming pool. A single acre of alfalfa typically requires 4.9 - 7.6 million liters a year for irrigation. Also, it's pretty easy to recycle the data center water, since it just has to cool and be sent back, but the irrigation water is lost to transpiration and the recycling-by-weather process.
So, even if there's no recycling, a data center that is said to consume "millions" rather than tens or hundreds of millions is probably using less than 5 acres of alfalfa in consumption, and in absolute terms, this requires only a swimming-pool or two of water per years. It's trivial.
I think the source is the bigger problem. If they take the water from sources which are already scarce, the impact will be harsh. There probably wouldn't be any complaints if they would use sewerage or saltwater from the ocean.
> Also, it's pretty easy to recycle the data center water, since it just has to cool
Cooling and returning the water is not always that simple. I don't know specifically about datacentres, but I know about wasting clean water in other areas, cooling in power plants, industry, etc. and there it can have a significant impact on the cycle. At the end it's a resource which is used at least temporary, which has impact on the whole system.
> If they take the water from sources which are already scarce, the impact will be harsh.
Surprised I had to scroll down this far to see this mentioned.
The water use argument is highly local and depends on where we are building these data centers. Are you building in the great lakes region with plenty of fresh water and no water scarcity issues (yet)? Ok fine.
But we aren't building there. We're building in Arizona, Nevada, Nebraska, Iowa putting further stress in an area that water scarcity is already an issue, or soon going to become one due to long term drought conditions. Or Texas, which already has problems with their power grid.
We're building in these locations because they're cheap. If we're going do to this, we need to not let the bottom line be the sole driving decision of data center locations. If it's not profitable to build elsewhere, don't build it until you've figured out how to make it efficient enough to where it is profitable.
People are critical of farmland and golf courses, too. But Farmland at least has more benefit for society, so they are more vocal on how it's used.