The diagram below shows how electricity is generated in a hydroelectric power station. Summarise the information by selecting and reporting the main features, and make comparisons where relevant.

The diagram illustrates the day-to-night steps of the generation of

electricity

from a hydroelectric power station.

Firstly

, the river flows into the high-level

reservoir

which is blocked by a dam to preserve

water

. During the daytime, when the intake below the dam is open, the

water

flows from the high-level

reservoir

through reversible turbines in the power station which operate as generators to the low-level

reservoir

. As turbines spin

while

water

runs through, they will generate

electricity

which will later be transmitted to the national grid through power lines and

then

be distributed for use.

In contrast

, during the nighttime, reversible turbines work in a reserve way, which means they will pump

water

back into the high-level

reservoir

from the lower one as the intake of the dam is closed. As the diagram displays, the generation of

electricity

from hydroelectric stations does not involve any procedure

that is

harmful to nature. In conclusion, it is an environmentally friendly way to produce

electricity

.