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Water: supply, demand and problems
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Water covers most of our planet, yet clean, fresh water is scarce in many places.
Where fresh water is
About 97% of the Earth's water is salt water in the oceans.
Of the small share that is fresh, most is locked in ice sheets and glaciers or stored as groundwater; only a tiny fraction is in rivers and lakes.
Areas have a water surplus where rainfall is greater than demand, and a water deficit where demand is greater than supply, as in much of the Middle East and North Africa.
Demand has risen over the past 50 years because of population growth, irrigation, industry and rising living standards.
Of the small share that is fresh, most is locked in ice sheets and glaciers or stored as groundwater; only a tiny fraction is in rivers and lakes.
Areas have a water surplus where rainfall is greater than demand, and a water deficit where demand is greater than supply, as in much of the Middle East and North Africa.
Demand has risen over the past 50 years because of population growth, irrigation, industry and rising living standards.
How water is used
Globally, roughly 70% of fresh water withdrawn is used for agriculture, mostly irrigation.
In developed countries a larger share is used by industry and homes (showers, washing machines, gardens).
In developing countries most water goes to farming, and domestic use per person is much lower.
In developed countries a larger share is used by industry and homes (showers, washing machines, gardens).
In developing countries most water goes to farming, and domestic use per person is much lower.
Water supply problems
UK: most rain falls in the north and west, but most people live in the south and east, so the south east is under water stress. Demand peaks in summer when rainfall is lower, and ageing pipes leak.
Developing and emerging countries: many people lack access to treated water, rivers are polluted by sewage and industry, and some areas have low or unreliable rainfall.
Developing and emerging countries: many people lack access to treated water, rivers are polluted by sewage and industry, and some areas have low or unreliable rainfall.
Explain why south-east England suffers from water stress.
- It has lower rainfall than the north and west of the UK.
- It has a large and growing population.
- So demand is close to, or greater than, supply.
Answer: Low rainfall and high population density.
About 97% of Earth's water is salty; most fresh water is in ice and groundwater. Surplus areas have more rain than demand; deficit areas have less. Agriculture uses about 70% globally. The UK's south east faces stress from high demand and low rainfall; poorer countries face untreated water, pollution and low rainfall.
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