Resources and environment, Year 11: supply, insecurity and sustainable supplies (Water option)

stress; scarcity

HintThe milder term is also what you feel before an exam; the more severe term means a shortage.

The whyThe measure divides the renewable fresh water in an area by its population. Below 500 m³ per person is called absolute scarcity. Because it depends on population as well as rainfall, a rainy but crowded region can be water-stressed. UN-Water now also calls a country water-stressed when it takes 25% or more of its renewable fresh water.

Rain soaks into permeable rock and is held there; on impermeable rock it runs off the surface

HintThink of a sponge beside a dinner plate.

The whyGeology affects how much water an area has and where it is found. A layer of permeable rock that holds water is called an aquifer, and people reach it through wells and boreholes. On impermeable rock the water stays at the surface, in rivers, lakes and reservoirs.

Industry and power stations use more, and wealthier households use more at home

HintFactories, cooling towers, washing machines and showers.

The whyManufacturing and electricity generation need large amounts of water. As incomes rise, homes gain piped supplies, flush toilets and appliances, and people eat more meat and irrigated crops, which take a lot of water to produce. So use per person climbs as well as the number of people.

Infrastructure: pipes, pumps and treatment works

HintThe built network that carries a supply from source to tap.

The whyWater is only available to people if it can be cleaned, stored and delivered. Where a government or a household cannot pay for this, people rely on wells, streams or expensive water sellers. In 2024 about 2.1 billion people, one in four, lacked safely managed drinking water.

A hot desert (arid) climate: very low rainfall and high evaporation

HintThink of the Sahara.

The whyClimate is the main physical control on water supply. Regions near the Equator and in the wetter mid-latitudes, such as the Amazon basin, Canada and northern Europe, have a surplus. Deficit is not only about rain: it depends on demand too, so crowded regions with moderate rainfall can also be short.

waterborne

HintIt joins the liquid to a word meaning 'carried'.

The whyWhere clean water is short, people have to use sources polluted by sewage. The World Health Organization estimates that contaminated drinking water causes about 505,000 deaths from diarrhoea each year. In 2022 at least 1.7 billion people used a drinking-water source contaminated with faeces.

The hours spent walking to fetch it leave no time for lessons

HintThink of a journey made on foot, every day, carrying a heavy load.

The whyWhere the nearest safe source is far away, someone in the household must fetch water every day, and that job often falls to women and girls. Time spent fetching water is time not spent in school or in paid work, so water insecurity holds back education and income as well as health.

Crops and livestock need water, so with too little for irrigation yields fall

HintFarming is the world's thirstiest activity.

The whyAgriculture takes more fresh water than any other human use. When supplies run short, farmers irrigate less, crops fail and animals die. Food then becomes scarcer and dearer, so water insecurity can lead on to food insecurity.

They need large volumes for cooling, cleaning and processing

HintThink what stops machinery overheating.

The whyMost power stations use water to cool their steam, and industries such as steel, paper, textiles and food processing use it to wash and process materials. When water is rationed, output falls, workers lose pay and the country earns less.

It can reduce the flow of water reaching the country downstream

HintAsk who controls the tap, and who waits below it.

The whyMany rivers, lakes and aquifers are shared: 153 countries have land in at least one of the world's 286 shared river and lake basins. What the upstream country takes or pollutes, the downstream country loses. Most disputes are settled by agreements to share the water, but tension rises as demand grows.

It is very expensive: the plants cost a lot to build and use huge amounts of energy

HintThink of the bill for boiling or squeezing the salt out of an ocean.

The whyDesalination removes the salt from seawater to make fresh water. It gives a supply that does not depend on rainfall, which is why dry coastal countries with money and cheap energy rely on it. For most countries, saving water or storing more of it is far cheaper.

brine

HintThe same word is used for the salty liquid olives are kept in.

The whyTaking fresh water out of seawater leaves the salt behind in a smaller volume of water. This waste is much saltier than the sea, and releasing it near the coast can harm marine life. It is the main environmental disadvantage of desalination, alongside the energy used.

It stores water from the wet season and releases it when rivers are low

HintThink of saving in good months to spend in lean ones.

The whyRain does not fall evenly through the year, so much river water runs to the sea unused in wet months. A dam holds it back in a reservoir. The stored water can supply homes, farms and industry all year, and many dams generate electricity as well.

They are displaced and have to be resettled elsewhere

HintTheir homes and farmland end up under the surface.

The whyThis is the main social disadvantage of a large dam. Farmland, villages and historic sites are lost, and the people moved may be given poorer land or little compensation. Set this against the advantages: a secure water supply, irrigation, flood control and electricity.

Its flow falls, which harms habitats and water users downstream

HintLess in the channel means trouble for fish and for anyone further along.

The whyA transfer helps the receiving region, but the source river carries less water, so it can dry up in places, grow more polluted and carry less sediment to its delta. Large schemes are also very expensive and can flood land for canals and reservoirs. Your own example must show both sides.

Grey water

HintNamed after a colour between black and white.

The whyGrey water is not clean enough to drink, but it is fine for flushing toilets and watering gardens or crops. Using it for those jobs means less treated drinking water is needed. Homes and offices can be built with a second set of pipes to collect and reuse it.

Water is pumped out no faster than rain recharges it

HintCompare a bank account's withdrawals with its deposits.

The whyIf more is taken than soaks back in, the water table falls, wells run dry and, near the coast, salt water can seep in. Groundwater management means monitoring the level, licensing how much each user may pump and protecting the land where the aquifer refills.

water meter

HintGas and electricity supplies have one too.

The whyPaying for each litre gives people a reason to use less, so metering is a form of water conservation. Other measures are fixing leaking pipes, low-flush toilets, efficient appliances and collecting rainwater. Conservation cuts demand, which is usually cheaper than finding new supplies.

recycling

HintThe same word is used for sorting glass, paper and cans.

The whyTreated waste water is most often reused for irrigation, in industry and for cooling power stations. With further treatment it can be made safe to drink. Recycling means each litre taken from a river or aquifer is used more than once.

Simple, low-cost technology that local people can run and mend themselves

HintThink hand pumps, rain tanks and spare parts from the nearest market.

The whyThis is called appropriate technology. A sustainable scheme also trains local people, is managed by the community and does not take more water than is replaced. When you write about your own example, show why it will still be working in twenty years.