[lesostep]

>> Water which is evaporated is also returned to the ecosystem. It falls back out as rain.

No, not necessary to the same one. Every body of water has a catchment area, and through the bottom parts of some lakes/rivers water sips into the earth, filling underground water levels.

Now, let's say you life on a coast with a regular winds in the ocean direction.

You basin fills with water evaporated by you, your neighbors catchments and – sometimes – ocean (wind doesn't always blow in one direction). But the large percentage of the water you evaporate goes into the ocean. Let's say 90 percent falls again on your catchment area, 10 percent falls in ocean but is regained through neighbors basins evaporation.

Now, if you increase your evaporation, you could easily drain a lot of water from your land.

[AnthonyMouse]

> Now, if you increase your evaporation, you could easily drain a lot of water from your land.

At which point we're back to the quadrillion watt hours of sunlight you get a day, which evaporates such a large amount of water that you have to be doing something pretty dramatic to move the needle. Which thermal power plants and data centers don't, but agriculture? It's pumping trillions of gallons of water out of the ground and into fields in that sun.

[yreg]

Why can't they condense the vapor on site? Or simply use closed cooling loops? Would it be that much more expensive?

[AnthonyMouse]

The premise of evaporative cooling is that the phase change absorbs an enormous amount of heat and carries it away. The heat is returned when it condenses back into water, so doing it on-site would defeat the purpose.

Hypothetically you could recondense it somewhere else, i.e. get a large land area and then capture the rainfall. Probably the big win there would be to take the water which is currently routed into the ocean from storm drains and recover it instead of doing that with it.