Hydro is mostly (not entirely) tapped out for power generation (not, of course, for pumped storage, which doesn't require rivers). Creating reservoirs is also e

Hydro is mostly (not entirely) tapped out for power generation (not, of course, for pumped storage, which doesn't require rivers). Creating reservoirs is also ecologically damaging, and releases a lot of methane (although I'm not sure how large the impact is relative to the carbon savings, this could be FUD I'm repeating)