Hydroelectric power works much the same as tidal power but in one constant direction. Hydroelectic power is a very clean energy source. It gives off no byproducts or greenhouse gases into the atmousphere , but, it has problems. Some negative effects are flooding, soil erosion, siltation, pollution, and habitat destruction, especially of endangered species. Its a difficult option to pass up but the stakes are quite high.
Over the past two decades large sections of glacier, Many of them dwarfing Rhode Island, have broken off from the Antarctic Glacial Shelf and fallen to the sea.
A short summary of how nuclear power is generated through nuclear fission.