The diagram illustrates the method of electricity generation at a twin-level hydroelectric power station.
As per the diagram, during the day, water is released from the reservoir at the top via narrow pen-stock pipes to fall forcefully into the turbines placed at a low-level. The swift rotation of the turbine thus created converts mechanical energy into electrical energy in the generators and the power thus generated is stored at the power house. As per the demand, this is supplied via high- capacity power lines to the national grid. The water which passes past the turbine is channeled to a low-level reservoir, and is stored there for recharging the reservoir at the top.
At night, the flow of water to the turbine is inversed by shuttering the reservoir at the top and releasing water from the low-level reservoir. Water which passes past the turbine is pumped upwards to the top-level reservoir by the mechanical force created by the turbine movement. The power generation process is continued by a reverse action in the day.