Band 8.5 IELTS Writing Task 1 Model Answer

Overall Band Score: 8.5 · Cambridge IELTS 14 · 2026-09-08

IELTS Writing Task 1 question

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.

Student answer (Band 8.5)

The diagram illustrates the cyclical process by which a hydroelectric power station generates electricity.

Overall, the system operates in two distinct, time-dependent phases. During the day, the station utilizes the downward flow of water to produce power, whereas at night, the machinery reverses its function to pump water back to its starting point, establishing a continuous and sustainable loop.

During the daytime electricity generation phase, water sourced from a river is held in a high-level reservoir behind a large dam. The intake near the base of the dam is opened, allowing water to flow forcefully downward through a channel. This rushing water drives reversible turbines located at the bottom, which subsequently operate a generator within the power station. The resulting electricity is then transmitted via power lines to the national grid, while the displaced water continues its path into a low-level reservoir.

Conversely, during the nighttime phase, the station's operation is completely inverted for water recovery. The intake at the high-level reservoir is closed to halt the downward flow. The reversible turbines then switch their function from generating to pumping. They draw the stored water from the low-level reservoir and propel it back up through the same infrastructure into the high-level reservoir. This essential step ensures that an adequate water supply is replenished and ready for the next day's power generation.

AI examiner evaluation

Task Achievement / Task Response — Band 8.5

The response is excellent. You have clearly identified the main features of the hydroelectric power station and provided a logical summary of the two-phase process. The overview is well-crafted, highlighting the cyclical nature of the system. You have successfully selected key details, such as the role of the reversible turbines and the function of the reservoirs, and presented them in a clear, comparative manner. All parts of the task are addressed, and the information is accurately derived from the diagram. The development of ideas is balanced, ensuring the reader understands both the generation and the recovery phases without unnecessary repetition.

Coherence and Cohesion — Band 8.5

The response is logically organized, with a clear progression from the introduction to the two distinct phases of operation. Paragraphing is used effectively to separate the daytime generation from the nighttime recovery. Cohesive devices are used naturally and unobtrusively, such as 'Conversely,' 'subsequently,' and 'This essential step,' which help guide the reader through the process. The flow of information is smooth, and the relationship between the different components of the power station is clearly established. There is no evidence of mechanical or repetitive use of linking words.

Lexical Resource — Band 8.5

You demonstrate a wide and sophisticated range of vocabulary that is highly appropriate for a technical description. Phrases like 'cyclical process,' 'time-dependent phases,' 'reversible turbines,' and 'infrastructure' show a high level of lexical control. The word choices are precise, and the collocations are natural, such as 'propel it back up' and 'replenished.' There are no errors in word choice or spelling, and the vocabulary used is both flexible and precise, contributing significantly to the clarity and professional tone of the report.

Grammatical Range and Accuracy — Band 8.5

The response exhibits a wide range of grammatical structures with full flexibility and accuracy. You effectively use complex sentences, such as 'During the daytime electricity generation phase, water sourced from a river is held in a high-level reservoir behind a large dam,' which combines participial phrases and prepositional modifiers seamlessly. Punctuation is used correctly throughout, and there are no grammatical errors. The control over verb tenses and sentence construction is excellent, making the text very easy to read and understand.

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