Water Supply and Use (Cambridge (CIE) IGCSE Geography)

Global Water Supplies

Global water supply

• Only 2.5% of the water on Earth is freshwater

• Approximately 68.7% of freshwater is stored in glaciers and ice sheets and 30% is groundwater

• The remaining 1.3% of freshwater is in rivers, soil moisture, lakes and the atmosphere

  • This is not evenly distributed across the globe—Canada contains more lakes than the rest of the world combined

(note: due to rounding of figures, the % on the pie chart to the right adds up to 99.9%)

Water supply

• The supply of water humans use comes from three main sources:

  • Lakes and rivers

  • Aquifers

  • Reservoirs

• Other sources of water supply include: 

  • Desalination 

  • Rainwater harvesting—collecting water that falls as precipitation

Groundwater/aquifer

• Water stored underground

• The water has filtered through soil and rocks

• It is obtained by drilling boreholes or digging wells

• When all the rock is fully saturated with water, it is an aquifer

• Groundwater may also come to the surface as a spring

• Issues with groundwater/aquifers include:

  • Overuse or over-abstraction of water in some areas means that aquifers do not have time to recharge through precipitation

  • Pollution from industry, agriculture and domestic waste can leach into the groundwater

Surface water

• Water is stored in lakes, reservoirs, and rivers

• Issues with surface water include:

  • Pollution from industry, agriculture and domestic waste can enter the water system through surface runoff

  • Dams are used to store water in reservoirs, but the construction of dams has slowed due to a lack of suitable sites and concerns regarding the environmental impact

Desalination

• The removal of salt from seawater means that it can be used for domestic, agricultural and industrial purposes

• Issues with desalination include:

  • Expensive to set up and run

  • Desalination plants use a lot of energy

Global water use

• Global water use by sector is: 

  • 70% agriculture—irrigation of crops and water for livestock

  • 20% industry—producing goods and generating energy

  • 10% domestic—toilets, cooking, cleaning, washing

• The use by sector varies across countries depending on whether they are MEDCs or LEDCs

Water demand

• The global demand for water is increasing

• Between 1934 and 2014, demand increased from 1 trillion m³ to 4 trillion m³

Water use in MEDCs

• 11% Domestic

• 30% Agriculture

• 59% Industry

Water demand in MEDCs

• The water demand in MEDCs is higher than in LEDCs for the following reasons:

  • Improving living standards—people have more appliances/sanitation that use water

  • Increased use of water in leisure and tourism—water parks, golf courses

  • Increased urbanisation 

  • Increasing industry—water is needed for the production of goods and energy production

  • Increasing use in agriculture—more water is needed for livestock

• The largest use of water in MEDCs tends to be industry

Water use in LEDCs

Water demand in LEDCs

• Unlike MEDCs, water use in LEDCs is mostly used for agriculture

• Many people are still dependent on agriculture 

• There is far less industry in many LEDCs so the demand for water for industrial processes is low

• Many people in LEDCs do not have access to piped water and, as a result, are more cautious with water use