Model answer:

The diagram (1)...............the process of electricity production in a hydroelectric power station. The process begins when the water flows from the river into a (2)........................and ends with the transmission of electricity to the national grid.

In general, the process is broadly (3)..................into day and night stages with the daylight stages involving electricity production from a river and storage of water in a reservoir. At night, the water flows (4).............in the opposite direction towards an initial reservoir and the river.

The day stage of the process involves (5)......................the river water into a high-level reservoir backed up by a dam. There is an (6).................area leading to the power station that opens during the day and closes at night. Water flows during the day to (7)....................electricity through the power station turbines. The generated electricity is then sent to a national grid through power lines while the excess water runs to a low-level reservoir.

During the night stage, the water stored in the low-level reservoir is (8).......................to the power station and the turbines of the generator pump it back into the high-level reservoir which is closed during the night. The river water is stored at the upper level and later it flows down, starting the cycle again.

ANSWER KEY

1. outlines 

2. high-level reservoir

3. distributed 

4. back 

5. channelling 

6. intake 

7. generate

8. reverted