Data center water cooling isn't a closed loop. They generally don't use it like PC water cooling. There are exceptions, but servers are typically air cooled.
What they did is look for a less energy intensive way to cool the air than traditional air conditioning. So they turned to evaporative cooling, and also misting the incoming air. This reduced their energy use, but at the expense of water use.
Most of the overall amount of "operational" water that Google used in 2021 is related to these data centers; it withdrew 6.3 billion gallons during that fiscal year, according to its 2022 Environmental Report. Of that amount, 1.7 billion was discharged.
They're evaporating away a lot more water than they return.