The diagram shows the process of water to generate electricity in a hydroelectric power station. There are several steps to make electricity.
First, the water from the river enters to the high-level reservoirs. Then, it flows down from the intake which is opened in a day to the reversible turbines through the pipes. During the day, the water operate generator. After this, generated electricity goes to national grid through power lines and remained water stores in the low-level reservoir.
At night, the process is quite different. First, the water starts from the low-level reservoir to reversible turbines. In the reversible turbines, stored water is pumped into high-level reservoir. The water goes along the pipe which is the same one that flows to generate electricity during the day. It goes to high-level reservoir passing underneath the dam.
Overall, large equipment is required to make electricity in a hydroelectric power station and the main characteristic of generating electricity is different height of the water.