Short answer: Water is a recurring IELTS theme covering scarcity, sanitation and clean supply, so precise words such as desalination, irrigation, aquifer and potable are a quick route to a higher Lexical Resource band.
The 30 words below include a meaning, a natural collocation and an example sentence ready to drop into an essay or Speaking answer.
Water questions appear regularly in IELTS: shortages and how to manage them, access to safe drinking water, irrigation and agriculture, the pollution of rivers and seas, and whether water should be free or priced.
Because the theme recurs so reliably, its vocabulary can be prepared in advance — and a writer who discusses water scarcity, desalination and sanitation instead of "not enough water" and "dirty water" reads at once as a higher-band candidate.
This guide gives you 30 genuine Band 7+ water words, each with the collocation that makes it usable and an example sentence in an essay-style context.
Why topic vocabulary lifts your Lexical Resource band
In both Writing and Speaking, Lexical Resource is one of four assessment criteria, each carrying equal weight, so it accounts for a full quarter of your mark on those papers.
The public band descriptors state that Band 7 requires "a sufficient range of vocabulary to allow some flexibility and precision" and the use of "less common lexical items… with some awareness of style and collocation", as set out in the official IELTS Writing Task 2 band descriptors.
Preparing topic vocabulary in advance is the most efficient way to meet that standard on a predictable subject like water.
The honest caveat is that the descriptors reward accuracy, not decoration. A less common word placed in the wrong collocation — "make a desalination", "a big scarcity" — reads as reach without control and can lower your band rather than raise it.
That is why every entry below pairs the word with its natural partners. For a structured month of building this kind of active, in-context vocabulary across topics, follow our 30-day vocabulary plan.
30 Band 7+ Water words
Read down the table for the meaning, then across to the collocation and example — the example shows the word doing the job it would do in a real answer.
| Word | Meaning | Collocation / common usage | Example sentence |
|---|---|---|---|
| scarcity | a shortage; a supply that is insufficient for demand | water scarcity, acute scarcity | Water scarcity is expected to affect two-thirds of the world's population within a few decades. |
| desalination | the removal of salt from seawater to make it drinkable | a desalination plant, desalination technology | Desalination plants supply fresh water to arid coastal cities, but they consume enormous amounts of energy. |
| irrigation | the supply of water to land or crops to help growth | an irrigation system, drip irrigation | Efficient drip irrigation can grow the same crops with a fraction of the water. |
| aquifer | an underground layer of rock or sand that holds water | an underground aquifer, deplete an aquifer | Over-pumping has depleted aquifers faster than rainfall can refill them. |
| potable | safe and clean enough to drink | potable water, a potable supply | Millions of people around the world still lack access to potable water. |
| sanitation | systems for supplying clean water and disposing of waste | water and sanitation, poor sanitation | Poor sanitation allows waterborne diseases such as cholera to spread rapidly. |
| reservoir | a large natural or artificial lake used to store water supply | a reservoir, reservoir levels | After months of drought, reservoir levels fell to a record low. |
| groundwater | water held underground in the soil and in rock | groundwater reserves, extract groundwater | Contaminated groundwater can take generations to recover. |
| drought | a prolonged period of abnormally low rainfall | a severe drought, prolonged drought | A prolonged drought devastated the region's harvest and emptied its wells. |
| catchment | an area from which rainfall drains into a river or reservoir | a catchment area, a river catchment | Deforestation in the catchment area increased the risk of flooding downstream. |
| evaporation | the process by which a liquid turns into vapour | rapid evaporation, reduce evaporation | Covering canals reduces the evaporation that wastes precious water in hot climates. |
| contamination | the presence of harmful substances that make water impure | water contamination, chemical contamination | Industrial waste caused severe contamination of the river and its estuary. |
| runoff | rain or excess water that flows off the surface into rivers | agricultural runoff, surface runoff | Agricultural runoff carries fertilisers into rivers, triggering harmful algal blooms. |
| purification | the process of removing impurities to make water clean | water purification, a purification process | Simple purification methods such as boiling can make unsafe water drinkable. |
| precipitation | rain, snow or other water that falls from the atmosphere | annual precipitation, low precipitation | A year of below-average precipitation left the reservoirs half empty. |
| hydroelectric | relating to electricity generated by flowing water | hydroelectric power, a hydroelectric dam | Hydroelectric dams provide clean energy but can displace entire communities. |
| sewage | waste water and human waste carried away in drains | raw sewage, treat sewage | Raw sewage discharged into the sea poses a serious public-health risk. |
| reclamation | the recovery of used water for reuse, or of land from the sea | water reclamation, land reclamation | Treated wastewater is increasingly used for reclamation, then supplied to farms and industry. |
| saline | containing salt; salty | saline water, saline intrusion | Over-extraction near the coast allows saline water to seep into freshwater wells. |
| wetland | land that is saturated with water, such as a marsh or bog | a coastal wetland, drain wetlands | Wetlands filter pollutants and buffer coastlines against storm surges. |
| depletion | the reduction of something to a critically low level | groundwater depletion, resource depletion | The depletion of underground water supplies threatens long-term food production. |
| tributary | a smaller stream or river that flows into a larger one | a tributary of, feed a tributary | Pollution in a single tributary can degrade the water quality of an entire river. |
| arid | very dry, with too little rainfall to support much vegetation | an arid region, an arid climate | In arid regions, every drop of rainfall must be captured and stored. |
| distribution | the way in which water is shared out or delivered | water distribution, uneven distribution | The uneven distribution of fresh water leaves some regions in surplus and others in crisis. |
| filtration | the passing of water through a filter to remove impurities | a filtration system, sand filtration | A basic filtration system removes most sediment and bacteria from river water. |
| abundant | existing or available in large quantities | an abundant supply, abundant rainfall | Regions with abundant rainfall often take their water security for granted. |
| conservation | the careful use and protection of a natural resource | water conservation, conservation measures | Simple water conservation measures, such as fixing leaks, save millions of litres each year. |
| salinity | the concentration of salt in water or soil | high salinity, rising salinity | Rising salinity in the soil eventually makes farmland unusable. |
| replenish | to fill up or restore a supply that has been used | replenish groundwater, replenish supplies | Winter rains slowly replenish the aquifers that supply the city. |
| inundation | the flooding of land with water | seasonal inundation, flood inundation | The seasonal inundation of the plains deposits fertile silt across the fields. |
How to turn these words into marks
Learn each word inside its collocation, not on its own: memorising "potable" is close to useless, but "access to potable water" or "invest in desalination plants" gives you a ready-made phrase you can drop in without a grammar risk.
Use one or two precise items per paragraph where they are natural, and keep the rest of your English plain — accuracy outscores a sentence stuffed with impressive nouns you cannot control.
To make these words active, meet them in context: our water reading practice generates Cambridge-style passages on this theme so you see the collocations working in real sentences, and the daily Word Coach gives you a word a day with practice in using it, which is how vocabulary moves from "recognise it" to "produce it under exam pressure".