Unfamiliar readers have to note that here sustainable is not used in its normal meaning but in the one used by some environmentalists. Hydropower can definitely be sustained indefinitely. It does cause flooding in some area previously I flooded and disturbs fish which some people view as an issue.
It’s really hard to have a good discussion about climate change because some people constantly push unrelated agenda into the mix.
That’s absolutely not what “sustainable” means.
The difference between “renewable” and “sustainable” isn’t a fringe concept. It’s been pretty well accepted for about 55 years now.
And even in the specific meaning you are pushing, the actual impact of hydro is questionable. Until you take a die hard position that no ecosystem whatsoever should be disturbed the benefit vs loss analysis is more than compelling.
Definition #2:
> the quality of not being harmful to the environment or depleting natural resources, and thereby supporting long-term ecological balance:
I would imagine this varies, but is a much smaller problem than e.g. heating up water habitats (data center cooling) or burning fossil fuels.
Geothermal completely slipped my mind! facepalm Obviously the consensus view is that geothermal is sustainable. I have some mild concerns about how many years a installation in a non-geologically/thermally active area can run before it changes the temperature of its lithic heat sink enough to significantly reduce power output, but many installations are proving the success of the technology overall, and that's more an economic challenge (lifetime/ROI of installation) than a question of sustainability.