Key features to report

• The process is a cycle with two modes: a daytime generating mode and a night-time pumping mode, so the answer must describe both and the switch between them.
• Water from a river is stored in a high-level reservoir behind a dam, and an intake at the foot of the dam is open during the day and closed at night.
• By day, water flows down a pipe to the power station, where reversible turbines operate a generator; electricity is sent along power lines to the national grid.
• After passing through the turbines in the day, the water flows into a low-level reservoir.
• At night, the flow is reversed: water is drawn back from the low-level reservoir and the reversible turbines pump it up the pipe into the high-level reservoir.
• The key components are the dam, high-level reservoir, intake, pipe, power station, reversible turbines, generator, power lines, national grid and low-level reservoir; use these labels accurately.

Model overview

Overall, the station operates as a reversible cycle between two reservoirs at different heights. During the day, water flows downhill to drive turbines that generate electricity, whereas at night the same turbines pump the water back uphill so that it can be reused.

Paragraph plan

1. 1

   Introduction

   Paraphrase the task: the diagram illustrates how a hydroelectric power station produces electricity and how it operates differently by day and by night.

2. 2

   Overview

   Summarise the process as a cycle between a high-level and a low-level reservoir, with water generating electricity as it flows down during the day and being pumped back up at night.

3. 3

   Body paragraph 1: daytime generation

   Describe the stages in order: river water collects behind the dam in the high-level reservoir, the intake opens, water flows down the pipe to the power station, the reversible turbines operate the generator, electricity goes through power lines to the national grid, and the water flows into the low-level reservoir.

4. 4

   Body paragraph 2: night-time pumping

   Explain that the intake is closed and the flow is reversed: water is drawn from the low-level reservoir into the power station, where the turbines act as pumps and push it back up into the high-level reservoir, ready for the next day.

Useful comparisons

• Organise the body by time of day: one paragraph for the daytime generating stage and one for the night-time pumping stage.
• Contrast the two functions of the reversible turbines: operating the generator by day and pumping water into the high-level reservoir at night.
• Contrast the intake settings: open during the day, closed at night.
• Follow the direction of the water: downhill from the high-level to the low-level reservoir by day, uphill in the opposite direction at night.
• Trace the electricity separately: from the generator along power lines to the national grid.
• Emphasise the cyclical nature of the process in the overview and final sentence, since the water is reused each day.

Band 8+ model answer

210 words · An original model answer written for ieltswrites, not an official answer. It stays in English, as in the exam.

Why this answer scores highly

Task Achievement

The answer covers every stage of both modes, presents a clear overview of the two-way cycle, and highlights the dual role of the reversible turbines without adding outside knowledge.

Coherence and Cohesion

Dividing the body into daytime and night-time paragraphs mirrors the diagram, and sequencing devices such as begins with, there, then and as a result make the order of stages clear.

Lexical Resource

Labels are paraphrased and extended with precise process vocabulary such as held back, channelled, drive, reversed and act as pumps, avoiding mechanical copying.

Grammatical Range and Accuracy

Present simple passives describe the process accurately, mixed with active verbs, relative clauses and purpose clauses such as so that it can be reused.

Useful vocabulary

hydroelectric power station

a plant that uses moving water to produce electricity

reservoir

a large natural or artificial lake used to store water

dam

a wall built across a river to hold water back

intake

the opening through which water enters the pipe from the reservoir

reversible turbines

turbines that can turn in either direction, either generating power or pumping water

generator

a machine that converts movement into electricity

the national grid

the network of power lines that supplies electricity across a country

be channelled

be directed through a pipe or passage

drive the turbines

make the turbines turn

the flow is reversed

the water starts moving in the opposite direction

be pumped back up

be pushed uphill by a machine

cyclical process

a series of stages that repeats continuously

subsequently

after that; used to show the next stage

whereupon

immediately after which; a formal sequencing word

Common mistakes

• Describing only the daytime stage and leaving out the night-time pumping, which is half of the process.
• Using active verbs throughout instead of passive forms such as is stored, is channelled and is pumped, which are more natural for a process.
• Adding information that is not in the diagram, such as how a turbine works internally or the environmental benefits of hydroelectric power.
• Missing the overview, or writing an overview that simply lists the stages instead of summarising the day and night cycle.
• Mixing up the reservoirs, for example saying water is pumped into the low-level reservoir at night.
• Copying the labels word for word as whole phrases, such as Night: pump water into high-level reservoir, rather than integrating them into grammatical sentences.

Frequently asked questions

Which Cambridge book is this question from?

This diagram of a hydroelectric power station is Writing Task 1 of Test 3 in Cambridge IELTS 14 Academic, published in 2019.

Should I use the passive voice for this process?

Use the passive where the action matters more than who does it, for example water is stored and is pumped back, but mix it with active verbs such as the turbines operate the generator for variety.

How should I organise a process diagram with day and night stages?

After the introduction and overview, write one body paragraph for the daytime generating stage and another for the night-time pumping stage, following the direction of the water in each.

How many words should I write for this Task 1?

Write at least 150 words; about 170-200 words is enough to describe every stage clearly without adding information that is not shown.