Water Quality & Supply (Edexcel IGCSE Geography)

Variations in water quality

• Clean, potable water is essential for human consumption, irrigation and for livestock

• Approximately one-quarter of the world's population does not have access to clean, potable water

  • Unsafe water results in an estimated 1.2 million deaths worldwide each year

• In areas with low precipitation water can become stagnant

  • Diseases which spread in polluted water include typhoid, cholera, bilharzia and dysentery

• There are many sources of water pollution

  • It is estimated that globally 80% of wastewater enters the water system without being treated

Main sources and impacts of pollution

• Human activity is the main source of water pollution

Agriculture

• Pollutants from agriculture enter the water in several ways:

  • Wastewater from silage and slurry

  • Fertilisers, herbicides and pesticides dissolve in rainwater

  • Soil erosion

  • Traces of medicine from those used to treat animals

• This impacts the water through:

  • the death of fish and other river wildlife which introduces bacteria into the water

  • eutrophication

  • poisoning fish and other wildlife

  • more sediment entering the river which increases turbidity, leading to a decrease in oxygen levels

Industry

• Industry pollutes water in several ways including:

  • spillages of oil

  • when water is used as a coolant and returned to rivers at higher temperatures

  • toxic substances from industrial processes being released into rivers

• The impacts on the water quality are that:

  • oil stays on the surface of the water, wildlife and plants become coated in oil and cannot eat/move/fly 

  • animals and plants within the water system cannot survive in higher temperatures

  • toxins enter the food chain and are harmful to wildlife and humans

Domestic

• Domestic premises also discharge pollutants water into rivers through:

  • untreated sewage

  • water which has been used for washing clothes and bathing

  • water which has been used for leisure may be treated with chlorine

  • traces of medicines taken by humans

• This impacts water quality because:

  • it increases the levels of nitrogen in the water and introduces bacteria

  • chemicals used in washing powder/liquid, bleach, shower gels, and soap all can be harmful to wildlife

  • chlorine is bleach which affects wildlife causing chemical burn

  • medicines are difficult to remove in water treatment

Storage & supply of clean water

• An estimated 1 in 4 people do not have access to clean drinking water

  • In developed countries over 90% of people have access to clean water

    • This is due to better water supply and storage infrastructure

  • In some developing countries, poor water supply and storage infrastructure means over 60% of people don't have access to clean water

• Water infrastructure ensures that people receive clean, potable water

• Water is collected from rivers, lakes, reservoirs and aquifers - the amount taken from each depends on location

  • In arid areas, people rely more on groundwater

• Water supply aims to take water from the source to where it will be used

• Where there is effective infrastructure, water is collected, treated and delivered

Collection

• Dams and reservoirs are used to collect and store water

  • Dams are built across river channels creating a store of water upstream

  • They are also used for preventing flooding and providing hydroelectric power

• Wells and boreholes allow access to groundwater

• Almost 50% of the world's drinking water comes from groundwater sources

• Groundwater is a significant source of water in arid areas where there is less surface water

• Due to the rising demand for water, groundwater abstraction is increasing

  • Levels of water in over 30% of the world's aquifers are decreasing faster than they were in 1980

  • In some areas, this is causing subsidence

    • The San Joaquin Valley, California has experienced a drop in ground level of nine meters over a 50-year period

  • Water is being abstracted so fast that the groundwater does not have a chance to recharge

Pipelines

• Water is usually transferred via pipelines

• Developed countries have a more extensive and effective pipeline infrastructure than developing and emerging countries due to the high cost

• Large-scale water transfer projects are used to take water from areas of water surplus to water deficit

  • The Tagus-Segura Project in Spain and the South-North Water Transfer Project in China are examples of this

Desalination

• Removal of salt from seawater is known as desalination

  • Currently, only 1% (2025) of the world's water is from desalination

• Desalination is an expensive process and uses lots of energy

  • This means the majority of plants are in developed countries

Treatment

• All water, even groundwater is likely to have some contaminants

• Developed countries and urban areas in developing and emerging countries have treatment works:

  • Water goes through a series of processes including filtration and disinfection

  • The treatment process removes solid waste, bacteria, viruses, fungi, minerals and chemical pollutants

• In rural areas and some urban areas in developing and emerging countries water may be treated where it is going to be used due to a lack of treatment works

Delivery to users

• Water is often delivered by pipeline directly from the treatment works to homes and factories

• Pipelines and infrastructure are expensive and need to be maintained

• Developing and emerging countries, particularly in rural areas, are less likely to have this infrastructure

• In urban areas in developing and emerging countries, standpipes may be used which are shared by many people

• In rural areas in developing and emerging countries, wells are the main water source but this is usually untreated