Hydro-electric power is power that comes from reservoirs in rivers using gravitational potential energy. The water flows from the upper reservoir to the downstream river, which turns a turbine between the two power sources. The energy from the turbine gets converted into kinetic energy and powers a generator, which stores the energy as electrical energy. The full process from the reservoir to the generator goes from Gravitational potential energy from the upper reservoir, to kinetic energy to spin the turbine, which will produce kinetic energy to charge the generator, which will finally store the energy as electrical energy.