Urban Rainwater Harvesting and Treatment Process
A complete IELTS Academic Writing Task 1 question with a model answer of 209 words, plus a breakdown of the sentence structures, cohesive devices and vocabulary that answer uses. Write your own version first, then compare.
Written by Manish Sharma · CELTA and DELTA qualified · 8 years teaching IELTS
Score my answer to this questionThe question
You have 20 minutes. Write at least 150 words.
The diagram below shows how rainwater is collected from rooftops and city surfaces, then treated and distributed for use in an urban area. Summarise the information by selecting and reporting the main features, and make comparisons where relevant. Write at least 150 words. [Process Stages] 1. Rainfall lands on rooftops, paved streets, and public squares. 2. Gutters and surface drains channel the runoff into screening grates that remove leaves and large debris. 3. Filtered water flows into an underground storage tank where heavier sediments settle at the bottom. 4. The clarified water is pumped up to a sand-and-gravel filter to remove smaller particles. 5. After filtration, the water passes through an ultraviolet (UV) disinfection chamber to kill bacteria. 6. Treated water is held in a clean-water reservoir and tested for safety. 7. Pumps push the treated water through pipes to households (for non-drinking uses) and to parks for irrigation. 8. Any excess flows to a city aquifer for groundwater recharge.
How to approach it
- 01Group the stages into phases (collection, treatment, distribution) for a clear overview
- 02Use the passive voice for describing technical processes: 'is pumped', 'are removed'
- 03Sequence with linking words: 'initially', 'subsequently', 'finally'
- 04Do not invent stages; describe only what the diagram shows
- 05Mention both inputs (rainfall) and outputs (households, parks, aquifer)
- 06Avoid copying the bullet labels word for word — paraphrase
Model answer
209 words in 5 paragraphs. Read it after you have written your own, not before: the point of a model answer is to show you what you missed, and you cannot miss anything you have not attempted.
The diagram illustrates the stages by which rainwater is captured from urban surfaces, treated, and supplied to households, public parks, and underground aquifers.
Overall, the process can be divided into three main phases: collection from rooftops and paved areas, multi-stage purification, and final distribution for non-drinking domestic use and ecological recharge. Both natural settling and mechanical filtration are employed before disinfection.
In the initial phase, rainfall lands on rooftops, streets, and public squares, after which gutters and surface drains direct the runoff into screening grates. These grates filter out leaves and other large debris before the water enters an underground storage tank, where heavier sediments are allowed to settle at the bottom under gravity.
The treatment phase then begins as the clarified water is pumped upward into a sand-and-gravel filter that traps smaller particles. The filtered water subsequently passes through an ultraviolet disinfection chamber, where harmful bacteria are killed. The treated water is held in a clean-water reservoir and subjected to routine safety testing.
Finally, pumps deliver the purified supply through a network of pipes to households for non-drinking purposes such as toilet flushing and laundry, and to parks for irrigation. Any surplus is channelled to a city aquifer, replenishing local groundwater reserves and completing the urban water cycle.
What this answer actually does
Measured from the text above, and compared against the other 38 answers of the same type in this library. These are counts, not band scores: they describe what the writing does, which is the part you can copy.
1.5 more than the median answer for this task type
10 words at the shortest, 29 at the longest
the same as the median answer for this task type
carry a subordinate or relative clause
Sentence rhythm
Sentences average 20.9 words and vary by 6 words either side of that, running from 10 words to 29. Variation is the point. Grammatical Range and Accuracy rewards a mix of simple and complex sentences, and an answer where every sentence is the same length reads as flat no matter how correct it is. 3 of the 10 sentences here carry a subordinate or relative clause.
The cohesive devices it uses
5 in total, spread across 3 different functions. Range matters more than count: an answer that opens every paragraph with a sequencer signals its structure but never signals a relationship between ideas, and Coherence and Cohesion is marked on both.
such as
subsequently, finally, then
overall
Vocabulary and repetition
Ignoring grammar words, 85 per cent of the content words in this answer are distinct, and 73 per cent appear exactly once. Lexical Resource is where repetition costs the most marks, and the usual cause is not a small vocabulary but reaching for the same noun every time the topic is named.
The longest run of words copied straight from the question is 9 words. Examiners discount wording lifted from the question, so a short run here is the right outcome: the answer restates the topic in its own words rather than borrowing the question's.
What you are marked on
All four criteria carry equal weight, and your Writing band is their average rounded to the nearest half band.
Task Achievement
Cover all stages and identify the main phases
Coherence & Cohesion
Sequence stages clearly with appropriate linkers
Lexical Resource
Use accurate process and water-treatment vocabulary
Grammatical Range & Accuracy
Use the passive voice and sequencing structures accurately
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