Water scarcity

Not enough water for the people who need it: water scarcity is the limited availability of water to human societies. It is measured by how much of the water available is already being taken out each year.

Remember it as: Taken out, divided by what is there: the bigger the share, the scarcer the water.

Reading a scarcity map: Pattern first: 'scarcity rises in many countries, most near the equator and in the mid latitudes'. Then a named country and its direction: 'Sahrel rises from 10-20% to over 40%'.

Real example: in 2023 the World Resources Institute found that 25 countries, home to a quarter of the world's people, face extremely high water stress every year: they use over 80% of their supply.

A country, not a region: When asked for a country, give a country's name: 'Europe' or 'Africa' is a region and scores nothing. For a change, give the place AND whether scarcity rises or falls.

The first kind of scarcity is about nature: the water is simply not there. This is physical water scarcity.

Remember it as: Physical: the water is not there.

Real example: Jordan is one of the driest countries on Earth. Most of it is desert, it has very few rivers, and each person has less than 100 cubic metres of renewable water a year.

People can make it worse: Physical scarcity is not only climate. A river that is over-used, so it no longer reaches the sea, is physically scarce because of people.

The second kind is about money and building. The water is there, but the infrastructure is not. This is economic water scarcity.

Remember it as: Physical: no water. Economic: no pipes.

Real example: the Congo River carries more water than any other river in Africa, yet most people in the Democratic Republic of the Congo have no safe water at home. There are too few pipes, pumps and treatment works.

High rainfall is not the same as no scarcity: A country with heavy rain can still be short of water. If people cannot store it, move it or make it safe, that is economic scarcity.

Scarcity gets worse when demand rises or the usable supply falls. Each factor below is a change, and climate change is one of them.

Remember it as: More people, richer diets, thirstier farms, a hotter climate.

Real example: Lake Chad, in West and Central Africa, has shrunk by about 90% since the 1960s. Droughts cut the rain, while a fast-growing population took more of its water for irrigation.

It must be a change: 'The area has a dry season' or 'it has low rainfall' does not explain an INCREASE in stress. Say what changes: 'less rain because of global warming'. For climate change, name the change AND its effect on water.

Both farms and growing cities make water scarcer. They change how much water there is (its availability) and how clean it is (its quality). A dirty river is water people cannot use.

Remember it as: Farms drink most; cities dirty most; both can do better.

Real example: in 2007 a huge bloom of toxic algae, fed by fertiliser from farms and sewage from towns, covered Lake Taihu in China. About 2 million people in the city of Wuxi had no drinking water for days.

Weigh both, both ways: In a 'which does more harm' essay, give farms AND cities, quality AND availability, harm AND the fixes each can make. Then decide.

Population growth affects water at two scales: local (a town, a lake, an aquifer) and regional (a whole river basin or country). Most effects are harmful; one can help.

Remember it as: More mouths, more fields, more factories, less water left.

Do not forget the good news: Growing demand can push people to invent and save: recycling, drip irrigation, better management. One point in a [7] can be a positive effect.

When water is scarce, its users compete for it. A conflict over water is a dispute between two users who want the same water.

Real example: the Colorado River supplies about 40 million people in seven US states and Mexico. In 2022 its main reservoir, Lake Mead, fell so low that Arizona, Nevada and Mexico had their shares cut, setting farmers against fast-growing cities.

A supply problem is not a conflict: 'Less snow is falling' or 'the pumps need electricity' are problems of supply. A conflict needs two sides: 'farmers who irrigate v the city that needs drinking water'.

There are two ways to fight scarcity: change how people use and value water, or build technology that makes more water or wastes less. Desalination often uses reverse osmosis and leaves salty waste, brine.

Real example: Singapore has little land to store rain, so it built 'Four National Taps': rain caught in reservoirs, water bought from Malaysia, NEWater (used water cleaned to drinking standard, able to meet up to about 40% of today's demand) and desalinated sea water. It also prices water at its full cost, adds a water conservation tax and runs campaigns.

A conclusion that scores: 'Technology is needed where scarcity is severe, but changing behaviour tackles the root cause and is affordable everywhere, so the two work best together.' Back it with your named examples.