A modular hydroelectric power plant which converts energy of water flowing in a stream into electric power. The plant comprises a plurality of modules which are removably mounted on piers embedded in a river or stream bed. Each module comprises a turbine over which water flows to rotate the turbine, and turbine rotation is converted into power by a generator attached thereto. The generator is removably mounted on the module. Insertion of the plant in a stream or river does not significantly disrupt flow therein, and locks are provided to assist vehicles in transversing the plant area of the river or stream.