Water Security (AQA A Level Geography)
Revision Note
Sources of Water
Achieving water security means trying to obtain and manage sufficient water of a high enough quality to meet current and future needs
This needs to be done sustainably, so that environmental and local community impacts are minimised
Only 2.5% of water in the global hydrological cycle is freshwater
Of that, only 0.9% is easily accessible surface water
Humans have extracted water from various sources, including rivers, lakes and aquifers
Technological innovation has seen new sources in the form of the desalination of seawater and recycling
Sources of Water for Human Use
Source | Explanation and Examples |
|---|---|
River abstraction | Collecting water directly from a river is the oldest method of obtaining water Thames Water which serves London and southeast England gets 70% of its water from rivers |
Reservoirs | Storage lakes, sometimes natural but often constructed, fed by rivers Welsh Water manages 91 reservoirs and obtains 95% of its water from river abstraction or reservoirs |
Boreholes into the water table | Wells are sunk through permeable surface layers to penetrate the water table Groundwater is pumped to the surface either with machinery or through natural artesian pressure Thames Water obtains 30% of its water in this way |
Pumping from aquifers | Aquifers are confined layers of saturated rock, deeper than the water table They are capped top and bottom by impermeable rock When bored into, the substantial pressure it is under forces groundwater to rise The Nubian Sandstone Aquifer System is underneath the eastern end of the Sahara Desert and is an important source of water for Egypt and surrounding countries It contains an estimated 150,000 km3 of groundwater |
Snow and glacier melt | An important source for irrigation and urban industrial use for countries located near high mountains 60% of Iran’s freshwater comes from its melting glaciers Meltwater from glaciers in the Himalayas feeds the Indus, Ganges and Brahmaputra rivers which are used by 700 million people Climate change is threatening to cut off this source for many regions |
Desalination | Evaporation of seawater to distil fresh water Requires large amount of energy and produces salt as a by-product 40% of freshwater in Israel is desalinated |
Water recycling and reuse | The process of treating wastewater using machinery or chemicals so that it can be reused, usually for industrial or agricultural purposes 90% of irrigation in the Valley of Mexico is from recycled water This can also recharge groundwater supplies through percolation |
Examiner Tip
This section of the course links to the core topic on water and carbon. If the exam question asks about sources of water, see if you can link your answer to the various key terms in the global hydrological and drainage basin water cycle. For example aquifers are a store of groundwater and are impacted by infiltration and percolation rates
Water Demand
Components of Water Demand
The components of water demand describe how water is used in different ways:
Agricultural use includes irrigation for crops and livestock management
Industrial use includes cooling for machinery and uses in product manufacture and processing
Domestic use includes water used in households and public buildings
The factors affecting a place’s use of water include:
Level of development
Nature and structure of economy
Climate
Effectiveness of water collection methods
Effectiveness of water storage methods
Effectiveness of water distribution networks
Population total, growth rate and density
These components vary over time:
Global water demand increased by more than 700% in the 20th century
It is forecast to increase even more sharply in the 21st century
In 1900, agriculture accounted for 90% of global water consumption, with industrial and domestic use making up the other 10%
Today, agriculture still accounts for 70%, with industry using 22% and domestic use at 8%
Farm irrigation is the largest single human use of freshwater
These components also vary over space:
Water demand is greatest across Asia, North America and Europe
Countries at different levels of development have different component ratios
In the UK, 75% of water is used in industry, 22% for domestic and 3% for agriculture
In Bangladesh, 95% is used for agriculture, 4% for domestic and only 1% for industrial use
Examiner Tip
As well as asking about the different components of water demand, a 6 mark exam question might ask for an analysis of the spatial and temporal variations. Be sure to be able to describe how the demand varies in different parts of the world, as well as how it varies over time
Water Stress
There are various ways to describe the difficulty in obtaining enough freshwater of sufficient quality to serve the needs of a population
In 2014, 36 countries faced extremely high levels of water stress
1.1 billion people
More than 80% of the water available to agricultural, domestic and industrial users is withdrawn annually
Leaves businesses, farms and communities vulnerable to scarcity
Examiner Tip
When describing the countries most affected by water stress, be sure to think about the various physical and human factors that have led to that situation
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