In the reader, tap any word or sentence to hear it in English,
translate it, or look up a definition.
Words to know
distillation
cleaning a liquid by boiling it and cooling the steam
kilowatt
a unit for measuring electric power
wastewater
dirty water that has already been used
ultraviolet
a kind of light the eyes cannot see, used to kill germs
reservoirs
large stores or lakes that hold water for a city
atmospheric
relating to the air around the earth
evaporation
the change of a liquid into a gas that rises into the air
conservation
the careful use of something so that less is wasted
A Earth is often called the blue planet, yet very little of its water is fit for human use. Around 97 percent of the world’s water is salt water in the oceans. Roughly two thirds of the fresh water that remains is frozen in glaciers and ice sheets, above all in Antarctica and Greenland. Less than 1 percent of all the water on Earth flows through the rivers, lakes, and shallow underground stores that people can reach. Demand keeps growing: agriculture alone takes about 70 percent of the fresh water used worldwide, and billions of people face a shortage for at least part of the year. The problem, in short, is not how much water the planet holds but where it lies and what form it takes.
B One answer is desalination, which takes the salt out of seawater. The oldest method, thermal distillation, boils the water and then cools the steam back into pure liquid; it is still common in the Persian Gulf, where fuel is cheap. Most modern plants use reverse osmosis instead. Pumps force seawater at high pressure through membranes whose tiny pores hold back the salt. Reverse osmosis needs around 3 to 4 kilowatt-hours of electricity for each cubic meter of drinking water, far less than thermal plants burn but still several times the energy needed to treat river water. Israel meets a large share of its household demand with plants on the Mediterranean coast, such as Sorek, which opened in 2013.
C A second path is to use the same water more than once. Windhoek, the capital of Namibia, has turned used water back into drinking water since 1968. Singapore’s NEWater program, officially launched in 2003, cleans wastewater with fine filters, reverse osmosis, and ultraviolet light. Water treated this way can be purer than many rivers, and the process needs less energy than desalination. The main barrier lies in people’s minds: many dislike the thought of drinking water that once ran through a sewer. For that reason, water companies often mix recycled water into reservoirs instead of piping it straight to homes.
D Where the sea is far away, the air itself can be a source. In the dry north of Chile, people have caught fog since the middle of the twentieth century by hanging fine mesh nets on hillsides; large projects that supply whole villages began in the 1980s. Droplets settle on the fibers and drip into tanks below, and one large net can gather several hundred liters on a foggy day. One of the largest systems of this kind stands on Mount Boutmezguida in Morocco, where it supplies villages that once relied on wells and trucked water. Machines called atmospheric water generators can also pull moisture from damp air, though they demand considerable power for every liter.
E The cheapest new source of fresh water, however, is the water that is wasted now. In some cities, more than a third of the treated supply leaks from old pipes before it ever reaches a tap. Farms that flood whole fields lose huge volumes to evaporation, losses that drip lines could largely avoid. Saving a liter almost always costs less than making a new one; consequently, many experts place conservation ahead of any new technology. Meeting the world’s need for fresh water will rest not on one dramatic invention but on careful use combined with every source described above.
Exam practice
Exam-style questions written by ESLDesk for practice.
They are not official IELTS or TOEFL questions, and ESLDesk is not affiliated with the exam providers.
True / False / Not Given
Do the following statements agree with the information in the passage?
Choose True if the statement agrees with the passage, False if it
contradicts the passage, or Not Given if the passage does not say.
Roughly seven out of every ten liters of fresh water used globally go to farming.
Show answer
True — Para A: agriculture alone takes about 70 percent of the fresh water used worldwide.
Sorek is the largest desalination plant in Israel.
Show answer
Not Given — Para B names Sorek only as an example on the Mediterranean coast; it never compares the sizes of Israel's plants.
Recycled water is normally piped directly into people's homes.
Show answer
False — Para C states the opposite: companies often mix recycled water into reservoirs instead of piping it straight to homes.
On days with fog, one big net in Chile can collect hundreds of liters of water.
Show answer
True — Para D: one large net can gather several hundred liters on a foggy day.
Many experts believe that developing new sources of water matters more than reducing waste.
Show answer
False — Para E states the opposite: many experts place conservation ahead of any new technology.
Matching Headings
The passage has 5 paragraphs, A–E.
Choose the best heading for each paragraph from the list below. There are two extra headings you will not use.
A second life for used water
Agriculture's growing demand for water
Why saving water costs less than making it
Turning the sea into drinking water
Harvesting moisture from the air
A watery planet with little to drink
Where cheap fuel keeps old methods alive
Show answer
vi. A watery planet with little to drink — Para A: nearly all water is salt or ice and under 1 percent is reachable — abundance without usability.
Show answer
iv. Turning the sea into drinking water — Para B describes desalination methods that turn seawater into drinking water.
Show answer
i. A second life for used water — Para C covers reusing wastewater as drinking water in Windhoek and Singapore.
Show answer
v. Harvesting moisture from the air — Para D is about drawing water from the air: fog nets and atmospheric water generators.
Show answer
iii. Why saving water costs less than making it — Para E argues that saving a liter almost always costs less than making a new one.
Summary Completion
Complete the summary below. Choose no more than two words
from the passage for each answer.
Only a tiny share of the planet's water is usable by people, since most fresh water is locked away in 1 and ice sheets. To create more, coastal countries remove salt from seawater, usually by forcing it through thin 2 that trap the salt. Cities such as Windhoek and Singapore instead clean 3 until it is pure enough to drink, while dry regions hang mesh 4 that catch droplets of fog. Even so, many experts say that cutting waste is cheaper than producing any new supply.
Show answers
glaciers — Para A: 'frozen in glaciers and ice sheets.'
membranes — Para B: 'through membranes whose tiny pores hold back the salt.'
wastewater (also accepted: used water) — Para C: 'cleans wastewater with fine filters' and 'turned used water back into drinking water.'
nets — Para D: 'hanging fine mesh nets on hillsides.'
