Global Water Supplies
Global water supply
- Only 2.5% of the water on Earth is freshwater
- 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
Sources of Water
(note: due to rounding of figures the % on the pie chart to the right add 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:
- Desalinisation
- Rainwater harvesting - collecting water that falls as precipitation
| Source of water supply | Information | Issues |
| Groundwater/Aquifer | Water stored underground that 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 |
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 which is stored in the lakes, reservoirs and rivers. |
Pollution from industry, agriculture and domestic waste can enter the water system through surface run off Dams are used to store water in reservoirs, but the construction of dams has slowed due to lack of suitable sites and concerns regarding the environmental impact |
| Desalinisation | The removal of salt from sea water to mean that it can be used for domestic, agricultural and industrial purposes | Expensive to set up and run - they use a lot of energy |
- 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
- Water demand is higher in MEDCs than LEDCs as a result of:
- Improving living standards - people have more appliances/sanitation which 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 Use in LEDCs
Water demand in LEDCs
- Unlike MEDCs the 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
Worked example
Study Fig 1, which is a map showing information about the percentage of the population in each country with access to clean drinking water
Fig 1
Describe the distribution of countries where 75% or less of the population have access to clean drinking water
[3]
- Answer:
- Mainly/most in Africa [1]
- Except Egypt and South Africa/except in North and South [1]
- A few/some in Asia [1]
- Near/on equator/mainly in tropics/between Tropics of Cancer and Capricorn/Central Africa/sub-Saharan Africa [1]
- Uneven/clustered [1]
Exam Tip
When describing the distribution from a map ask yourself the following questions;
- What is the general pattern?
- Does the pattern relate to anything else for example the location of LEDCs and MEDCs?
- Are they near the equator or further away?
- Is the pattern uneven or clustered?
Use map features to help with your description - place names (countries and continents) compass rose, latitude and longitude, the equator and the tropics
