Doesn't decarbonation imply replacing something? Lots of places with the right distributions of water use hydroelectric, because it was cheaper to build out. Ontario has craploads of water (hello, great lakes) but not much elevation, at least not in the right places.
Funny enough, "electricity" and "hydro" were synonymous in Toronto when I lived there in the early 90's because of Ontario Hydro. It was named for the electricity coming from Niagara Falls, but then yeah... like you said.