The problem is not killing what lives in said water. And many times we the public become aware something damages the ecosystem when the damage is extensive, and some people never acept the fact, much less any responsibility.
Edit: In this specific case, the best case scenario is saving half the energy expenditure. Larger and more intrusive infrastructure with unknown effects for saving less than half the energy. Let's hope they always use renewables, btw.
I totally agree about the consequences needing to be understood, but in the end, if it comes to this, it’s water. We can’t survive more than 3 days without water. We will boil the oceans if we need to