Hydropower is the most prevalent renewable energy technology worldwide with the highest installed capacity. Much of this capacity is large scale. Small and medium scaled hydropower is of greater sustainability with potential for expansion.

Why Sustainable Hydro Matters to Local Governments

Sustainable hydro power comes from small-scale systems which allow rivers to keep their natural function as home to wildlife.   These smaller projects are of a manageable size for local governments and have the potential to yield great benefits.  

The Technology

There are a number of hydropower technologies, including impoundment, diversion, and pumped hydro storage. Impoundment is the typical large-scale system that dams water and holds it in a reservoir to be released when electricity is needed via a generator. Released water turns a turbine(s) that drives a generator, producing electricity.  In a diversion (run of river) hydro system, instead of impounding the water behind a dam, only part of the river is diverted, and it is this diverted portion that flows through the blades of a turbine to generate electricity. This form of hydro has significantly less environmental impact and is where much potential for further development, as most large-scale sites are already in operation or are not socially and environmentally acceptable. The last form is pumped hydro storage, where the differential in height between two reservoirs serves to produce electricity when the upper reservoir is released to the lower reservoir as it passes through turbines. The process is repeated when off-peak electrical power is used to pump the lower reservoir back up to the higher reservoir. Pumped hydro storage is currently the most common form of energy storage. 

Read about Ocean Energy here, where wave and tidal power are discussed.