Since 1880–1890 when the first plants were built, hydropower has become an important source of electricity in many different countries all over the world (Koch 2002; Oud 2002). Hydropower was the first renewable energy to be developed on a mass scale and is now considered to be one of the most cost-effective means of producing clean renewable electricity. It is generally more efficient, more reliable and has a higher capacity factor than solar, wind, and marine energy (wave and tidal) technologies (Fraenkel et al. 1991; Mishra et al. 2011) and often offers a better energy payback ratio than other power generation technologies (British Hydropower Association and IT Power 2010).