People depend on water in so many ways. Rivers provide people with drinking water, irrigation for crops, habitat for fisheries, recreation opportunities like swimming and boating, and so many important cultural benefits. They also can provide a tremendous amount of energy through hydropower.

Hydropower dams can play an important role in helping developing economies transition to a cleaner energy system that also meets the needs of their people. But the environmental externalities — the side effects — of dams can be catastrophic.