The diagram illustrates how electricity is produced in a hydroelectric power station using water stored in reservoirs.
Overall, the process involves two main stages that occur during the day and night. In the daytime, water flows from a high-level reservoir to generate electricity, while at night the water is pumped back to the upper reservoir for reuse.
During the day, water from the river is stored behind a dam in the high-level reservoir. When the intake gate is opened, water flows down through a pipe towards the power station. As the water moves downward, it spins reversible turbines, which operate a generator to produce electricity. The generated electricity is then transmitted through power lines to the national grid. After passing through the turbines, the water is released into a low-level reservoir.
At night, the process is reversed. The intake gate is closed, and the turbines pump water from the low-level reservoir back into the high-level reservoir. This allows the system to store water again for electricity generation the following day.