Most of the water evaporates in the end. Once it rains down again, it can go through water treatment plants again and be reused. The other water contains everything that was in the original incoming water and concentrated forms of minor pollution for descaling. The contamination problem isn't that big compared to a farm or chemical plant.
Once the outside air crosses a certain temperature, air-to-air AC becomes less efficient and evaporative cooling can be used to get rid of heat instead.
Of course, this has the side effect of using more water during warm periods, when people and agriculture also need more water. That can be rather problematic in drought situations, especially in the decades to come.
It should be noted that evaporated water usually doesn't rain back down in the same place it evaporated from, so increasing the evaporation in one area does not guarantee a matching increase of rainfall there.
Once the outside air crosses a certain temperature, air-to-air AC becomes less efficient and evaporative cooling can be used to get rid of heat instead.
Of course, this has the side effect of using more water during warm periods, when people and agriculture also need more water. That can be rather problematic in drought situations, especially in the decades to come.