There is no international consensus on the definition of small hydro power. The upper limit varies between capacities of 2.5 and 25 MW in different countries, but a value of up to 10 MW is becoming generally accepted. Small hydro can be further subdivided into mini hydro (usually defined as <500KW) and micro hydro (<100kW). Whichever size definition is used ,small hydro power is one of the most environmentally benign forms of energy generation. 

Small-scale hydro-electric systems capture the energy in flowing water and convert it to electricity. Although the potential for small hydro-electric systems depends on the available of suitable water flow, where the resource exists it can provide cheap clean reliable electricity. If they are well designed, small hydro-electric systems blend with their surrounds and have minimal negative environmental impacts

Moreover, small hydro power has a huge, as yet untapped potential in most arts of the globe, and can make a significant contribution to future energy needs. It depends largely on already proven and developed technology, yet there is considerable scope for development and optimization of this technology.