If you need to cool both a power plant and a data center you are removing thousands of gallons out of the local areas. This is moisture content evaporated and succinctly placed back into the clouds. It does return, but not necessarily to where it came from or in the right means. It is now able to be moved out rather than stay in the water table.

This means wells dry up and natural cycles are disrupted. It usually is fresh water, readily drinkable and serviceable water. Reducing this from law abiding citizens who pay their taxes for profit.

This again assumes best possible case. Which realistically is impossible for maximizing and optimizing. A lot of places just evaporate water and get new one. Easier to take continuously from the source which will be cooled, than to wait or make a cooling infrastructure.

Its why laws in place for downstream were important. Someone fucks up above, you get fucked below. In pollution or diverting of water.