Earthquakes -- there is some causality

Destruction of fish habitat -- salmon in Columbia river

In general, making water go slow when it used to go fast has a lot more negative consequence for the environment than one might expect.

I find this episode of 99 percent invisible to be really informative -- https://99percentinvisible.org/episode/fish-cannon/

https://en.wikipedia.org/wiki/Environmental_impact_of_reserv...

The biggest is the destruction of migrating fish habitat, sometimes reversible with specialized structures (salmon ladders), sometimes not. There is also some evidence for increased CO2 emissions from artificial reservoirs.