There are about 1,000 hydropower plants in South Tyrol, and the vast majority of them are small or medium-sized – ranging from tiny ones powering a single farm, to clusters of more sizeable ones covering an entire valley"s supply. Most are run-of-river diversion plants, meaning a part of the stream is diverted, typically by small dams or weirs, through a pipe to a turbine. (There is no standard global definition of small hydro, and the upper limit can vary hugely between countries, but international reports tend to define it as up to 10 megawatt installed capacity. In South Tyrol, small typically means up to 220 kilowatt (kW) capacity, and medium, up to 3 megawatts [MW]). Elsewhere in the Alps, the picture is similar, with a multitude of small or mid-sized plants allowing individual farms or villages to be self-sufficient, while typically making a modest contribution of only around 10% or so to national hydropower production.