A hydroelectric power generator having a bulb turbine generator housed in a bulb shaped inner casing. The turbine runner of the generator is connected to a main shaft of the electric power generator. The outer casing is coupled to the inner casing by stay vanes. A draft tube is coupled to the downstream end of the outer casing. A liftable gate is positioned to retain water in the open channel and the outer casing is fixedly secured to the gate and vertically movable with it.