The presented graph illustrates the process in which electricity is produced by a hydroelectric power station.
Overall, the process of generating electricity involves four key stages, beginning with intaking water from reservoir and ending with distributing the generated power through the national grid.
At the starting point, there is a huge high-level reservoir located behind a dam, collecting water which comes from the river. The gates of the dam are opened during days, flowing the water towards turbines, and closed during nights, pumping water and recollecting in the reservoir. During the days, when the flow of water is toward turbines, it flows to a low-level reservoir in which the generator located, and the power station becomes active and produces electricity. In contrast, at nights the low-level reservoir become empty and the reversed flow can generate more power by flowing through the reversible turbines. The generated power goes to the national grid via the power lines.