[20after4]

There is another problem with evaporative cooling in regards to the effect on climate: water vapor has an incredibly strong greenhouse effect. It's complicated though, because white clouds have the opposite effect: they reflect heat back into space. I have no idea how you could begin to calculate the net effect from additional humidity introduced into the environment, you would have to somehow figure out how much becomes just humidity and how much contributes to more cloud formation.

[BehindBlueEyes]

There might also an effect on fish spawning if the temperature is higher, some fish may not return to spawn until the water is cool enough or they have lower chances of survival if they hatch early due to increased temperatures. That is, assuming the remaining water flow allows for passage of fish runs.