Japan used to have many dams for the electricity but then scaled them down (or not scale it up) due to environmental concern. I'm not sure it was a right call given the limited availability of options there. They are also strong anti-nuclear sentiment which I have some sympathy. However you need something you have to make a call.

This map says hydro share is like 8%. https://app.electricitymaps.com/map/zone/JP/live/fifteen_min...