Hydroelectricity is electrical energy generated when falling water from reservoirs or flowing water from rivers, streams or waterfalls (run of river) is channelled through water turbines. The pressure of the flowing water on the turbine blades causes the shaft to rotate and the rotating shaft drives an electrical generator which converts the motion of the shaft into electrical energy. Most commonly, water is dammed and the flow of water out of the dam to drive the turbines is controlled by the opening or closing of sluices, gates or pipes. This is commonly called penstock.
Hydropower is the most advanced and mature renewable energy technology and provides some level of electricity generation in more than 160 countries worldwide. Hydro is a renewable energy source and has the advantages of low greenhouse gas emissions, low operating costs, and a high ramp rate (quick response to electricity demand), enabling it to be used for either base or peak load electricity generation, or both.
Australia's hydro energy resources
Australia is the driest inhabited continent on earth, with over 80 per cent of its landmass receiving an annual average rainfall of less than 600 mm per year and 50 per cent less than 300 mm per year. There is also high variability in rainfall, evaporation rates and temperatures between years, resulting in Australia having very limited and variable surface water resources. Much of Australia's economically feasible hydro energy resource has already been harnessed.
Australia's hydro energy resources are described in more detail in the Australian Energy Resource Assessment, which provides an integrated scientific and economic assessment of all Australia's energy resources and factors influencing their development and use to 2030.
Australia has more than 100 operating hydroelectric power stations with total installed capacity of about 7800 megawatts (MW). These are located in the areas of highest rainfall and elevation and are mostly in New South Wales (55 per cent) and Tasmania (29 per cent). The Snowy Mountains Hydro-electric Scheme, with a capacity of 3800MW, is Australia's largest hydro scheme and is one of the most complex integrated water and hydroelectricity schemes in the world. The Scheme collects and stores the water that would normally flow east to the coast and diverts it through trans-mountain tunnels and power stations. The water is then released into the Murray and Murrumbidgee Rivers for irrigation. The Snowy Mountains Scheme comprises sixteen major dams, seven power stations (two of which are underground), a pumping station, 145km of inter-connected trans-mountain tunnels and 80km of aqueducts. The Snowy Mountains Hydro-electric Scheme accounts for around half of Australia's total hydroelectricity generation capacity and provides base load and peak load power to the eastern mainland grid of Australia.
Hydro energy is particularly important in Tasmania where it provides much of the state's electricity. The Tasmanian integrated hydropower scheme harnesses hydro energy from six major water catchments and involves 50 major dams, numerous lakes and 29 power stations with a total capacity of over 2600MW. The scheme provides base and peak load power to the National Electricity Market, firstly to Tasmania and then to the Australian network through Basslink, the undersea interconnector which runs under Bass Strait. There are also hydroelectricity schemes in north-east Victoria, Queensland, Western Australia, and a mini-hydroelectricity project in South Australia.