In the IELTS writing exam, you may be required to describe a process diagram. This will be part of writing task 1, a section in which you might normally expect to encounter a line graph, bar chart, or table.

Describing a process diagram might fill you with fear, but you shouldn’t worry too much. They always look much more difficult than they really are. While process diagrams may seem much harder than line graphs or bar charts, they are usually quite simple, and if you can avoid panicking, you should be able to write a strong essay.

In today’s lesson, I’m going to show you a step-by-step guide to describing process diagrams for IELTS.

Analyse the Question

First of all, as with any IELTS writing question, you must take a few minutes to analyse the question before you begin writing. Let’s look at an example 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 making comparisons where relevant.

Here is the diagram:

ielts writing process diagram hydroelectric power

And here is how it will look on the exam paper:

ielts writing process diagram hydroelectric power

So what do you need to do? The question tells us in pretty simple terms what the diagram is about, so we should read that first. In this case, it is all about generating (making) electricity. We can see from the picture that this is done using water (hydroelectric power).

Identify the Stages

When you are analysing the diagram, it is important to break it into different stages and put them in the correct order. Sometimes this is very easy… but sometimes it can be a little difficult. Looking at our example diagram from above, we can identify the following stages:

  1. Water flows from river into reservoir
  2. Water flows through intake to power station
  3. Turbines turn to generate electricity
  4. Electricity sent to national grid via power lines
  5. Water flows into lower level reservoir
  6. Water returns back to upper level at night

You might want to label the diagram this way:

annotated process diagram

Note that the order of events is not always 100% clear, and sometimes two or more things may happen at the same time. In the above example, I have listed #4 and #5 separately, even though they basically happen together. I did this because in my description I would like to link the electricity generator to the power lines because I feel that this is a logical connection. The excess water is more incidental, and would then be mentioned after.

Finding the Right Vocabulary

Many students panic when they see a process diagram because they think that there will be some complicated vocabulary that is needed. For example, there are sometimes diagrams about complex industrial or ecological processes… Can you imagine how difficult those would be to describe?!?!

Well, actually they are not that difficult. In fact, process diagrams usually contain most of the vocabulary that you need to describe them within the diagram. You just need to make some small alterations to the grammar.

Check out this video about how to describe a process diagram using the vocabulary included on the diagram:

Going back to our example from above, we can see that there is already a lot of information in the diagram, and we can use this to describe the process without having to rely on our own knowledge. (Let’s face it, most people don’t know the precise language required to talk about hydroelectric dams.)

We can see that the words “generate” and “generator” are already included on the diagram, and these are key to understanding what is happening. Another word, “flow” is written on the diagram, and this refers to the movement of water.

In order to avoid repetition, you might want to think of synonyms of these words:

Generate Flow
Make Move
Produce Pump

It is worth noting that “pump” is not exactly a synonym of “flow,” but it can contextually have a similar meaning when considering this diagram. You can also think of antonyms (words with the opposite meaning). An antonym of “flow” is “hold back.” You can see how I have used these words in my sample answer below.

Grammar for IELTS Writing Task 1

Your grammar must be very precise in IELTS writing task 1. When it comes to process diagrams and maps, you should be especially careful about article use. Remember that the reader should be able to visualise the image from your description, so you need to imagine that they cannot see it.

Considering that, you must use “a” when you first introduce something and then later use “the” to refer back to it. That’s because it is an unknown thing first but later it is known. This is explained in depth in this video lesson:

Passive Voice

While the passive voice is not very common in English, it is extremely common when people describe process diagrams for IELTS. This is because the passive voice is used when we don’t know who or what is doing an action, or don’t need to say. It is also useful when we put emphasis on the object of an action. For all those reasons, we really need it for this sort of task.

For example, rather than saying “______ generates electricity,” we can instead say, “Electricity is generated.” This is useful because we don’t know who is operating the power station, and we are not allowed to guess at this sort of thing in IELTS. If we wanted to include the fact that the process results in the generation of electricity, we could say it in one of two ways:

  1. The flow of water through a dam generates electricity.
  2. Electricity is generated by the flow of water through a dam.

The second one is passive voice, and it puts emphasis on the result, which can be more useful, especially if we are focusing on this in the introduction to our essay.

Here is another example:

  1. A dam holds water back from its natural course.
  2. The water is held back from its natural course by a dam.

Again, the second example is passive and puts emphasis on the water, which may be more important in that context. It also adds a degree of formality, as passive structures are a feature of formal writing.

Sometimes we can mix active and passive voice to give some diversity to our language:

  • The water flows into a lower reservoir, but at night it is pumped back up through the system to the upper reservoir.

The first example is active and the second is passive. In the first example, the water is more important than the reservoir, and having an active structure shows the relationship more clearly. Water —-> reservoir. In the second, we don’t need to say what is pumping the water, and we want the water to be more important, so we use passive voice.

Here is a video about using the passive voice in IELTS writing task 1:

Sample Answer

Here is my sample answer to the question and diagram above:

The diagram depicts a hydroelectric power station, and shows how electricity is generated by the flow of water through a dam and other component parts. Ultimately, water flows from one reservoir to another, producing electricity that is sent to the national grid.

Firstly, water enters a reservoir from a river. The water is held back from its natural course by a dam, underneath which there is an intake pipe that is open during the day and closed at night. During the daytime, water flows down, via gravity, to the power station, which is housed below the dam. In the power station, the flowing water spins a generator, which produces an electrical current that is then distributed via power lines to the national grid.

Once the water has generated this electricity, it flows into a lower reservoir, but at night it is pumped back up through the system to the upper reservoir, ready to begin the process again the following day.