Hydro-electricity is presently the largest contributor to renewable energy worldwide; in Australia and particularly in NSW.
Hydro-electricity also is more desirable than wind generation because of a higher capacity factor and ability to produce power on demand.
But hydro-electricity is resource constrained as it is difficult to build new dams in the developed countries that are presently heavy fossil fuel consumers.
Dams flood private property and/or National parks and have many self-interested and environmentally concerned opponents. Hydro-electric schemes interfere with natural river flows and related wildlife, particularly when they involve extensive inundation. It has become politically very difficult to construct new dams in Australia, even when the potential energy resource is significant.
Nevertheless in developing countries like China, India and Vietnam there are large hydro-electricity resources that remain unexploited.