This is an interesting story. I am not that familiar with the ecological impacts of a dam but some internet clicking here and there confirmed the story. A hydroelectric project does get in the way of fish migration and ecological balance. This is being experienced by Oregon's largest hydroelectric project, the Peltron Round Butte Hydro Project owned by Portland General Electric Company and the Confederated Tribes of Warm Springs.

Luckily, this project was certified by the Low Impact Hydropower Institute (LIHI) as one that passes their standards, thus receiving eligibility as a renewable energy resource. Hydro power without the LIHI approval cannot be certified as renewable energy and in so being will not enjoy the benefits of renewable energy resource classification.

What did the Butte Hydro Project do to mitigate its ecological impact? Create new fish passage systems, that's what. I have to do more research on that but I know that with what they did, they were successful.

Read more here.