The diagram illustrates how electricity is produced in a hydroelectric power station through several stages involving water flow between two reservoirs.
Overall, the process consists of two main stages that occur during the day and at night. During the day, water flows downward to produce electricity, while at night, the stored water is pumped back up to the high-level reservoir, making it a reversible and continuous cycle.
During the day, water from the high-level reservoir is released through an intake valve, which remains open. The water then flows down through a pipeline towards the power station, where it passes through reversible turbines. These turbines drive a generator to produce electricity, which is then transmitted via power lines to the national grid. After passing through the turbines, the used water is collected in a low-level reservoir.
At night, when electricity demand is lower, the process is reversed. The intake valve is closed, and the turbines operate in reverse, using some of the generated electricity to pump water back up from the low-level reservoir to the high-level one. This ensures that sufficient water is stored for power generation during the next day.