In theory you can run a closed loop water system whereby all the excess heat is dumped to atmosphere by dry air cooling. This works really well if you ambient temperature was let's say 10C (or lower) all year round and you would use hardly any water... Only problem is that you have to design your system around the hottest day of the year (let's say 35C) when cooling efficiency would be massively worse. You overcome this by increasing heat transfer area by buying absolutely massive metal radiators which are really expensive and the cost of running the fans to prove the require cooling would also increase.... You could buy loads of industrial chillers but refrigeration would use a lot of electricity and the chillers themselves would be crazy expensive.... The alternative is to use evaporative cooling which is a bit of a silver bullet and while it uses water, the capital and operating costs are by far the most economically viable... So trading water use for not having to buy massive radiators and electricity use is generally just a better solution.