Many designs in-between with air cooling, hybrid, etc.
Still a non-issue, it's going back into the water cycle.
Any water issue would be specific to the municipality, it's not a national issue, nor is it an issue specific to datacenters, it's true for anything being built in the town (golf courses, power plants, etc.)
If you use a hybrid design, you still evaporate ~80% of your cooling water - you just use less overall cooling water.
The water going back to the water cycle doesn't mean it's potable.
And yes, I do understand that it is a very small fraction of overall water use. I am actually in favor of using water where it will reduce electricity use. But let's not be inaccurate - the water used for cooling is absolutely evaporated or sent to sewage, with the exception of whatever sits inside the system's closed loop (which exists whether or not the system is cooled evap/dry/hybrid).
yeah... that's the point right?
Hybrid systems keep the primary process fluid in a closed loop, they spray water on pads to cool the coils during the hotter parts. Basically a stop gap when air cooling is not enough.
There's also close loop systems that lose none, it's just more expensive to build. They are already being deployed in areas with scarce water. Microsoft and a quite a few others already built a few.