Increasing Water Supply (AQA A Level Geography)
Revision Note
Written by: Robin Martin-Jenkins
Reviewed by: Bridgette Barrett
Catchment & Storage of Water
Balancing water demand with supply can be met by:
Increasing supply
Reducing demand
A combination of both
Methods of increasing storage capacity can be large-scale or small-scale
Whatever method chosen comes with pros and cons
Methods of Water Catchment and Storage
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Reservoirs - water captured naturally in drainage basins can be stored in artificial lakes, built by damming a valley | Large - water stored for use at regional or national scale | Three Gorges Dam, Yangtze river, China Aswan Dam, Nile River, Egypt | Controls flooding downstream by regulating river flow Huge volume of water can be stored and used in industrial, agricultural and domestic settings HEP power can be generated by turbines within the dam Recreational uses of the lake to include fishing and water sports | High economic cost of building and maintaining scheme Flooding of land to create reservoir destroys habitats and can displace communities Alteration of the natural river regime causes sediment to build up in the lake Reduction of sediment available for deposition downstream Increase in erosion downstream Can create microclimate around the lake, affecting humidity and wind speeds |
Rooftop rainwater harvesting - rain falling on roofs of buildings can be captured and stored in filtering tanks under gardens | Small - water used in domestic settings for individual households or small communities | In Bangalore, India, it is mandatory for buildings with a footprint of more than 200㎡ to harvest and utilise rainwater for internal use | Relatively cheap and easy to implement and maintain Provides self-sufficiency for households | Needs to have a relatively reliable supply of rainfall Only really effective for domestic settings |
Examiner Tips and Tricks
An exam question may ask you to assess the methods for increasing water supply. If so, make sure you introduce a ‘spatial’ element to your answer. For example, explain why large scale schemes might not work in some LICs due to their great expense, or why rooftop harvesting might not work in some desert areas due to a lack of reliable rainfall.
Diversion and Transfer of Water
Water diversion involves transferring captured water from areas of surplus to areas of deficit
Water can be drawn from
Aquifers
Rivers
Reservoirs
And pumped between drainage basins by
River diversions
Aqueducts
Canals
Pipelines
Examples include:
The Sindh Province in Pakistan
A network of irrigation canals transferring water from the river Indus to cropland
High evaporation rates in the canals reduces the effectiveness
China’s north-south diversion project
Planned to complete in 2050
To divert water 44.8 billion cubic metres of water annually from southern rivers to the population centres of the arid north
Expected to cost $62bn – more than twice as much as the Three Gorges Dam
Advantages of these schemes include:
Allows water to be supplied to regions that are water stressed
Localised droughts can be quickly addressed
Water can be transferred in large volumes to be used for agricultural, industrial and domestic purposes
Disadvantages of these schemes include:
They tend to be very expensive to build and maintain
Tend to be large-scale and so can have large impacts on the environment:
Can lead to major environmental deterioration if not sustainably managed
E.g. the Aral Sea in Central Asia
Reduced in size by 90%
Due to decades of heavy irrigation from river transfers in surrounding countries
Salt has been brought to the surface making the land infertile
Fishing industry has been destroyed
Examiner Tips and Tricks
If you are asked to assess water supply schemes or strategies then it is important to discuss the idea of sustainability. Think about whether the scheme provides for future as well as current population and discuss whether there is any negative impact on the environment (there usually is!).
Desalination of Water
Desalination
Involves the removal of salt from seawater to make it drinkable
Various methods either using heat or membranes to separate salt from the water
The two main methods are:
Distillation
The traditional way
Seawater heated and boiled
Steam produced is condensed
Salt left behind in boiler
Reverse osmosis
Seawater filtered at high pressure
Small tubes syphon off drinkable water
Saline solution left behind is pumped back to sea
Both methods are still used but reverse osmosis is more modern and efficient
Desalination plants are expensive to build and maintain, so mainly operate in HICs in water-stressed regions
E.g. Saudi Arabia - Water desalination has doubled over the past decade to reach 2.2 billion ㎥ in 2021, up from 1.1 billion in 2010
Oman, UAE, Australia and USA are the other biggest users of desalination
UK has a plant in Beckton, East London, which provides drinking water for 400,000 households
Examiner Tips and Tricks
Because of change over time, some geographical facts and figures become out of date quite quickly, so it is always good practice to keep searching for the latest figures on the internet and updating your notes as you do so. For example, desalination schemes are being built all the time in various parts of the world and you could check the latest figures as you are revising.
Impacts of Large Water Projects
Environmental Impacts of a Water Supply Scheme
The Aswan Dam was completed in 1970 across the Nile River in Southern Egypt
It was built as a solution for rising demand for water
Its reservoir, Lake Nasser, is estimated to store over 132km3 of water
The scheme aimed to reduce flooding downstream by regulating the flow of the Nile
It also provided irrigation for vast areas of arid farmland surrounding the lake
An HEP plant in the dam initially provided a renewable source of electricity to half of Egypt’s population
Rising demand for electricity has meant that this proportion has fallen to one tenth today
However critics of the dam point to several negative environmental impacts of its building and operation
Examiner Tips and Tricks
If you are asked for a case study of the environmental impacts of a major water supply scheme, you won’t just be expected to relay facts and figures about the scheme. Instead you will have to amylase, assess or evaluate the scheme in some way, so practise writing about both how the scheme helps supply water to the region and also how it brings negative impacts as well.
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