The Kaplan turbine is a water turbine that was invented in 1913-1922 by Viktor Kaplan. It has adjustable blades that allow it to efficiently handle a wide variation of water flows. The Kaplan turbine is well-suited for low head sites between 2-40 meters and has efficiencies over 90%. It is an inward flow reaction turbine where the water changes pressure and gives up energy as it moves through the adjustable blades, causing the runner to spin. The Kaplan turbine's adjustable blades make it more efficient at partial loads compared to other water turbines.