An uncertain future for global hydropower

Hydropower is still the leading source of electricity from renewable energy and for some countries, such as Norway, the dominant source of electricity. It is a fully dispatchable source of electricity, with a high efficiency of conversion from gravitational to electrical energy. The long life of hydro schemes—up to a century—potentially gives hydroelectricity a very high rate of energy return to energy invested. Hydro dams can serve multiple other purposes, such as flood control and recreation, although these purposes can sometimes be in conflict. However, hydro, especially large projects, may have a range of serious deleterious effects on both the natural world and humans, including large-scale population displacement and threats to freshwater ecosystems. Further, a variety of external factors, including climate change, will negatively impact on future hydro output. These impacts add uncertainty to the economic viability of planned hydro schemes and will likely lead to future hydro output being smaller than usual forecasts.