One destroys an ecosystem and fishery. The other moves water between ponds.

Never understood that to be honest.. we can today build quite excellent tunnels that are crossable for fishes.

https://www.youtube.com/watch?v=j_B5bZvCdJY

Just make it go to almost the same depth and you dont even loose water..

A dam is not the same as an aquarium. True experience is that dams destroy fisheries and drive extinctions. Almost always, the fishery had produced overwhelmingly more value than the dam.

Grand Coulee Dam should be demolished, but won't be.