Mostly salt, mostly ice, mostly far away: Only a tiny share of Earth's water is fresh and easy to reach, and it is spread very unevenly. Having water nearby is not the same as equitable access to it.
The points to remember
- About 97.5% of Earth's water is salt; only about 2.5% (often rounded to 3%) is fresh.
- Of the freshwater, about 69% is ice, 30% is groundwater and only about 1% is in lakes, rivers and soil.
- Much groundwater is deep and costly to pump; much river water is in remote places such as the Amazon and Siberia.
- So freshwater per person differs hugely between countries: availability is uneven.
- Who actually gets it depends on social, cultural, economic and political factors.
Remember it as: Mostly salt, mostly ice, mostly in the wrong place.
Groundwater is pumped from aquifers. The water that rain and snow refill each year is called renewable freshwater.
Real example: Canada has about 75,000 m³ of renewable freshwater per person each year; Egypt has under 600, almost all of it from the Nile, which rises in other countries.
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Nature sets the starting amount: A place's climate and its water stores decide how much freshwater it has. Climate change is now changing both.
The points to remember
- High precipitation and low evaporation (a cool, wet climate) give a place more freshwater.
- Large stores that refill (lakes, rivers, glaciers, aquifers) keep water flowing through dry seasons.
- Higher temperatures mean more evaporation: drier soils, shrinking lakes, saltier water, even desertification.
- Changed rainfall or more El Niño events: more water in some places, more droughts in others.
- Rising sea levels: seawater floods or seeps into coastal groundwater and makes it salty.
- Melting glaciers: in the short term more water in rivers; in the long term less, as the ice runs out.
Remember it as: Glaciers: short term more, long term less.
Real example: Swiss glaciers lost about 10% of their ice in just two years, 2022 and 2023. They feed the Rhine and the Rhône, so for now meltwater swells the rivers in summer, but as the ice shrinks less will be left for dry summers.
Two traps, and one rule: Each point needs the change (warmer, less rain, rising seas) and its effect on freshwater. 'Climate change causes problems' scores nothing.
Never write 'glacier retreat causes flooding', and never say the extra water comes from 'snowmelt': it is the glacier ice melting.
Papers often give a table of ice volume and ask for a percentage decrease. Write the formula first: percentage decrease = (old value − new value) ÷ old value × 100.
Worked example: Practice numbers: a glacier held 80 km³ of ice in 1900 and 30 km³ in 2020.
(80 − 30) ÷ 80 × 100 = 50 ÷ 80 × 100 = 62.5% decrease. Divide by the old value, and give the % sign.
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People, habits and beliefs: How many people there are, how they live and what they believe all change how much clean water there is, and who gets it. Social factors and cultural factors work together.
The points to remember
- Social: fast population growth and growing cities raise demand faster than pipes can be laid.
- New city homes are often in informal settlements with no piped water: people use wells or buy from sellers.
- Education and awareness: people who know how to save and protect water use it better.
- Gender roles: where women and girls fetch water, they lose hours each day, so access is not equal.
- Cultural: habits and beliefs decide how much water people use, and how they treat rivers and lakes.
- Religious rituals, such as mass bathing in a sacred river, can pollute it, so less is safe to drink.
- Culture can also help: old traditions of sharing water fairly between users.
Remember it as: More people, new homes, old habits: all change who gets the water.
Social, real example: Lagos, Nigeria, has grown to more than 15 million people. Only a small share of homes get piped water; most rely on wells, boreholes and water sellers, in many informal settlements.
Cultural, real example: in Bali, Indonesia, rice farmers have shared irrigation water for about a thousand years through the subak, now a UNESCO World Heritage site.
Name the factor, then the link: Say which kind of factor it is, then how it changes availability (how much usable water) or access (who can get it).
Money moves water: Water falls from the sky for free, but storing, cleaning and piping it costs money. Economic factors decide who can pay.
The points to remember
- Richer countries can pay for dams, pipes, treatment works and desalination plants.
- In poorer places the water may be there, but there is no money to pipe and clean it.
- Price: the poorest may not afford enough, and often pay more per litre than homes on the mains.
- Privatisation: a company runs the supply; it may invest, but prices can rise beyond what poor families can pay.
- Farms and industry take water and pollute it, leaving less clean water for homes.
- Polluted water is not usable without costly treatment, so less is available even if the volume is the same.
Remember it as: Rain is free; pipes are not.
Real example: in Kibera, a large informal settlement in Nairobi, Kenya, few homes have taps. People buy water by the container from kiosks, and pay more per litre than richer homes connected to the city's mains.
Not just 'they are poor': Link money to something specific: no pipes, no treatment works, or water too expensive to buy.
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Who controls the tap: Political factors decide who controls water. About 60% of the world's river flow crosses a national border, so many countries share their water.
The points to remember
- A country upstream can build dams or take water, so less reaches countries downstream.
- A treaty fixes each country's share; without a binding agreement, no share is guaranteed.
- Shared water can bring conflict: disputes, threats, and people who migrate when water runs out.
- It can also bring cooperation: joint commissions, shared data, shared dams and hydropower.
- Governance at home: laws against pollution, fair rules for sharing; corruption leaves pipes unbuilt.
- War and unrest can destroy pumps, pipes and treatment works and cut the supply.
Remember it as: Upstream holds the tap; a treaty shares it.
Conflict
- An upstream dam cuts the flow downstream.
- No treaty, so no guaranteed share.
- Shortage can push people to migrate.
Cooperation
- A treaty fixes each share.
- Joint commissions share river data.
- Shared dams give both sides hydropower.
Real example: Ethiopia's Grand Ethiopian Renaissance Dam on the Blue Nile began filling in 2020. Egypt and Sudan, downstream, fear that less water will reach them; Egypt gets almost all its water from the Nile. Years of talks have not produced a full agreement.
Show both sides: A long answer on shared water needs conflict and cooperation, each with a named river.
Plenty of water, few people, careful use: Some countries are unlikely to run short: they have lots of water, few people to share it, or the money and values to use it well. Ecocentric values help too.
The points to remember
- Climate: high precipitation and low evaporation.
- Large replenishable stores: lakes, rivers, glaciers and aquifers that refill each year.
- Money and technology: water harvesting, desalination and treatment add supply.
- Ecocentric values: people use water sustainably and pollute little.
- No conflicts with neighbours over shared water sources.
- Low population density: less demand from homes, farms and industry.
- A low standard of living: fewer appliances and less industry, so lower demand per person.
Remember it as: Lots of rain, big stores, few people, careful use, no fights.
Real example: Norway has a cool, wet climate, thousands of lakes and many glaciers, and only about 5.5 million people. It shares no big river with a thirsty neighbour, and about 90% of its electricity comes from hydropower.
Say why it lowers the risk: One reason per mark, each with its link: not 'it is rich' but 'it can afford desalination'. A low standard of living counts too: less use per person means lower demand.
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How this comes up: Paper 1: a fact file and a table on retreating glaciers. Outline the impact on water resources, then calculate a percentage decrease, one mark each.
Figure 1 is a fact file and a table about the glaciers of the Valdurna valley.
(a) Outline how glacier retreat may affect the water resources of the Valdurna valley.
(b) Calculate the percentage decrease in ice volume between 1900 and 2020.
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