Hydropower creates electricity.
Many fish die and they need fish ladders to go back up
my oppinan is that hydropower is a disadvantage because it can be very exspencive
Hydropower has high initial costs (meaning that dams are expensive to build), however their opperating cost is very low, since they don't require the purchase of fuel (like coal does or nuclear does).
It produces electricity without generating any emissions of greenhouse gases or other waste.