The diagram below shows how electricity is generated in a hydroelectric power station.
Sample Response
The process shows how electricity is generated in a hydroelectric power station. In general, the diagram can be broadly separated into day and night stages with the daylight stages involving the generation of electricity from a river and storage of water in a reservoir. At night the water flows back in the other direction towards an initial reservoir and the river. The first stage of the process involves channelling the river into a high-level reservoir backed up by a dam. There is an intake area leading to the power station that is open during the day and closes at night. Water flows during the day to generate electricity through the power station turbines and the resulting electricity is sent to a national grid through power lines while the water then continues to a low-level reservoir. The reversible turbines that operate the generator during the day allow the station to pump the water in the low-level reservoir back into the high-level reservoir for use the next day.
IELTS Writing Correction
- 1. Correct return destination Original: towards an initial reservoir and the river Suggested revision: towards the high-level reservoir Why it matters: The diagram shows water returning only to the high-level reservoir during the night phase.
- 2. Name the daytime phase Original: The first stage of the process involves Suggested revision: The daytime phase begins with Why it matters: This wording links the description more precisely to the diagram's day-and-night cycle.
- 3. Use precise reservoir wording Original: backed up by a dam Suggested revision: formed by a dam Why it matters: A reservoir is more naturally described as being formed by a dam.
- 4. Use the diagram label Original: an intake area Suggested revision: an intake Why it matters: The visual labels this component simply as the intake.
- 5. Sentence rewrite Original: In general, the diagram can be broadly separated into day and night stages with the daylight stages involving the generation of electricity from a river and storage of water in a reservoir. Suggested revision: Overall, water passes from the high-level reservoir through the station to generate electricity by day, then is pumped back uphill at night. Why it matters: This gives a clearer and more accurate overview of the two-phase cycle.
- 6. Sentence rewrite Original: Water flows during the day to generate electricity through the power station turbines and the resulting electricity is sent to a national grid through power lines while the water then continues to a low-level reservoir. Suggested revision: During the day, water flows through reversible turbines, which drive a generator; the electricity is sent by power lines to the national grid, and the water enters the low-level reservoir. Why it matters: The revision separates the simultaneous outputs clearly and presents the daytime sequence in an easier-to-follow order.
- 7. Sentence rewrite Original: The reversible turbines that operate the generator during the day allow the station to pump the water in the low-level reservoir back into the high-level reservoir for use the next day. Suggested revision: At night, the reversible turbines pump water from the low-level reservoir back into the high-level reservoir for reuse the next day. Why it matters: The original does not explicitly state that this reverse pumping occurs at night.
- 8. Separate the process phases Suggested revision: Use an introduction and overview first, then separate the daytime generation and nighttime pumping stages into distinct detail paragraphs. Why it matters: The single-paragraph format obscures the clear day-versus-night organization shown in the diagram.
Suggested Rewrites
- towards an initial reservoir and the river towards the high-level reservoir
- The first stage of the process involves The daytime phase begins with
- backed up by a dam formed by a dam
- an intake area an intake
- In general, the diagram can be broadly separated into day and night stages with the daylight stages involving the generation of electricity from a river and storage of water in a reservoir. Overall, water passes from the high-level reservoir through the station to generate electricity by day, then is pumped back uphill at night.
- Water flows during the day to generate electricity through the power station turbines and the resulting electricity is sent to a national grid through power lines while the water then continues to a low-level reservoir. During the day, water flows through reversible turbines, which drive a generator; the electricity is sent by power lines to the national grid, and the water enters the low-level reservoir.
Why this response received Band 7.5
The response gives a clear, accurate account of the full daily cycle, with a particularly effective overview of daytime generation and nighttime pumping. Its main limitation is occasional imprecision, especially the suggestion that water returns toward the river, and some stages are compressed into long sentences. Prioritize sharper directional wording and separate the generation and return phases more distinctly.
IELTS Writing Criteria Scores
Task Achievement
The overview identifies the two operating periods and the response accurately covers nearly every major stage shown.
Clarify that nighttime pumping returns water to the high-level reservoir rather than toward the river.
Coherence and Cohesion
The description progresses logically from storage through generation to the nighttime return cycle, with clear linking between stages.
Divide the long daytime sequence into shorter, more balanced sentences so each stage is easier to follow.
Lexical Resource
A suitable range of process vocabulary describes the reservoirs, intake, turbines, generator, and grid with generally good precision.
Replace vague expressions such as daylight stages and initial reservoir with the exact labels and directions shown.
Grammatical Range and Accuracy
Complex structures are handled accurately throughout, and the response contains a strong variety of clauses with very few errors.
Refine sentence boundaries in the longest process description to make the otherwise controlled syntax more concise.
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IELTS Academic Writing Task 1
The diagram below shows how electricity is generated in a hydroelectric power station.
Your response
Write the task yourself, then compare your choices with the annotated response.