Hydropower is energy derived from flowing water. More than 2,000 years ago, the Ancient Greeks used waterpower to run wheels for grinding grain, today it is among the most cost-effective ways discovered so far to generate electricity. An outstanding 99% of Norway’s electricity needs are met by hydropower. In many countries, micro-hydropower projects are significantly improving lives of many communities, in even the most remote locations.

The basic principle of hydropower is using water to drive turbines. The water’s kinetic energy – or energy of motion – is turned into mechanical energy, which is then turned by a generator into electrical power.

The largest hydropower plant is the 22.5 gigawatt Three Gorges project in China. It produces 80 to 100 terawatt-hours per year, which is equivalent to the yearly demand of 70 to 80 million Chinese households.

Hydropower plants consist of two basic configurations: the first based on dams with reservoirs and the second, run-of-the-river scheme (with no reservoir). Hydropower dams with a large reservoir can store energy over short or long time periods to meet peak demand. The dam scheme can also be sub-divided into small dams with night-and-day regulation, large dams with seasonal storage, and pumped storage reversible plants for both pumping and electricity generation. Small-scale hydropower is normally designed to run in-river, and is considered an environmentally friendly option since it does not significantly interfere with a river’s flow