Kaplan turbine runner. (Source: © Tunatura / stock.adobe.com)

Reaction water turbine with variable pitch for both the guide vanes and the runner blades. The runner has 3 to 12 blades and its shape resembles a propeller. The runner blades are adjusted by a mechanism hidden in the turbine body. Thanks to them, the Kaplan turbine adapts well to the actual flow, which is why it is used on rivers with larger but variable flow and lower heads.