Band 8.5 IELTS Writing Task 1 Model Answer

Overall Band Score: 8.5 · Cambridge IELTS 14 · 2026-09-03

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 how electricity is generated in a hydroelectric power station through a reversible process involving two reservoirs.

Overall, electricity is produced during the daytime when water flows from the upper reservoir through reversible turbines to the lower reservoir. At night, the process is reversed, with the turbines functioning as pumps to return water to the upper reservoir for reuse.

During the day, the intake at the dam is opened, allowing water from the upper reservoir to flow down through a large pipe towards the reversible turbines. As the water passes through these turbines, they operate as generators and produce electricity. The electricity generated is then transmitted to the national grid via power lines. Meanwhile, the water discharged from the turbines collects in the lower reservoir.

At night, the intake is closed and the direction of water flow is reversed. The reversible turbines then function as pumps, using electricity to pump water from the lower reservoir back up through the pipe to the upper reservoir. The water is consequently stored at a higher level, ready to flow down through the turbines again when the intake is reopened the following day. Thus, the same water can be repeatedly circulated between the two reservoirs to generate electricity.

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, specifically the cyclical nature of the process between the two reservoirs. You successfully contrasted the daytime electricity generation phase with the nighttime pumping phase. The overview is concise and effectively captures the core mechanism, and the body paragraphs provide a logical, step-by-step description of the process. All parts of the prompt are addressed, and the information is accurate based on the provided diagram. No key features were omitted, and the comparison between the two states is well-integrated into the narrative.

Coherence and Cohesion — Band 8.5

The essay is highly coherent and flows logically. You have used paragraphing effectively to separate the two distinct phases of the process. The use of cohesive devices such as 'Meanwhile', 'At night', 'consequently', and 'Thus' is natural and helps guide the reader through the sequence of events. The progression of ideas is smooth, moving from the general overview to the specific details of the daytime and nighttime operations. There is no evidence of mechanical or repetitive linking; the structure is sophisticated and supports the clarity of the explanation.

Lexical Resource — Band 8.0

You have demonstrated a strong command of vocabulary appropriate for a technical description. Terms such as 'reversible process', 'national grid', 'discharged', and 'repeatedly circulated' are used accurately and in the correct context. The range of vocabulary is sufficient to describe the process with precision and flexibility. There are no noticeable errors in word choice or collocation, and the language used is natural and precise throughout the response, which is indicative of a high level of lexical control.

Grammatical Range and Accuracy — Band 8.5

The grammatical control is impressive. You have used a variety of complex sentence structures, such as participial phrases ('allowing water from the upper reservoir to flow...') and subordinate clauses ('when water flows...', 'as the water passes...'). The majority of sentences are error-free, and the punctuation is used correctly to enhance readability. The tense usage is consistent and appropriate for describing a recurring process. There are no grammatical slips that impede communication, and the overall structure is sophisticated and error-free.

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