Imagine if you were a Yurok person and your people lived for thousands of years, as a unique culture, and where substituting off of salmon was integral to that culture, only to have foreign invaders remove you from your lands, put you on reservations, and effectively destroy the lifeblood of your people by damming the rivers. Now imagine how after several generations this would damage your people as a group economically.
Given that history, it seems strange to question that the Yurok people might have financial "benefits" from this kind of project.
You can see pictures of what these elevated river temperatures do here: https://english.alarabiya.net/News/world/2021/08/02/Scorchin...
Why is water depth so important? It's pretty well known how hot concrete can get when sitting in exposed California sun. If you have a water depth of a foot - that water is going to get really toasty.
There's quite a few resources regarding water temperatures and the effect it's having on salmon runs:
- https://www.kiro7.com/news/salmon-threatened-hot-temperature...
- https://www.ucsrb.org/low-water-high-temperatures-drastic-ef...
And in the end the real issue is ecological restoration, of which salmon are only a part. Fortunately the case is easy for these dams because the dams don't pay for themselves.
In general dams are pretty terrible, but like so many things can be worth the tradeoff. But the "worth" involves human life (e.g. wiping out the hetch hetchy valley so that people on the SF peninsula can have water). But when there's no clear benefit at all, the downsides (buildup of heavy metals behind the dam, damage to fish and other wildlife, earthquake risks....) are decisive.