GCSE Geography | Increasing Water Supply (Resource Management - Water 4)

In order to increase water security around the globe we need to find new sources or develop better ways of moving water from areas of surplus to areas of deficit. There are numerous solutions to the issue of water supply...

Dams and reservoirs

Dams block rivers and control the flow of water, enabling a store of water to build up behind it in a reservoir. Rainfall is collected and stored when precipitation levels are high and released gradually during drier periods.

Pros and cons

• The water can be transported and used for irrigation
• Dams can be huge in scale, which are controversial as they cost a lot of money, starve the river downstream of water and displace
  people upstream - such as the Three Gorges Dam in China (pictured below), the world's biggest dam which took 15 years to construct, cost $37 billion (£27 billion), and displaced 1.3 million people
• Or they can be very small - for example, cement dams which are just a few metres high - which then have a limited impact on water security
• The reservoirs can also lose a lot of water through evaporation

Diversion and storage

Where water supply is moved and stored for use at a later time - for example, in deep reservoirs or in permeable rocks below the ground.

Pros and cons

• Storage underground prevents water being lost through evaporation
• Tends to be fairly small scale and local, for example diverting some of the water from the River Severn to supply Bristol with water, by using canals

Water transfer schemes

These are schemes that take water from areas of surplus to areas of deficit through a network of canals and pipelines - and are on a much larger scale than diversion and storage projects. (Click here for information about water transfer schemes in the UK)

An example of a large-scale water transfer scheme is the South-North Water Transfer Scheme in China (SNWTS), which moves huge amounts of water from the humid south to the arid north. This region has experienced rapid population growth, and is home to 200 million people, including the megacities of Beijing and Tianjin. The region has also seen significant economic development, meaning there is a demand for irrigation for farming and water for thirsty manufacturing industries.

(Click here to find about China's South-North Water Transfer Scheme)

Another example is the Lesotho Highlands Water Project (LHWP), which transfers water from Lesotho to South Africa. Lesotho is an LIC and is landlocked, in fact it is entirely surrounded by South Africa! Lesotho has a water surplus - this is because it is a mountainous country with a high level of precipitation and a low population total. Whereas South Africa has a large population with uneven rainfall, particularly in the south and west. The LHWP involves the construction of dams (such as the Katse dam, pictured below), reservoirs and pipelines, and other infrastructure need to support water transfer, including roads and bridges.

(Click here to find about the Lesotho Highlands Water Project)

Pros and cons

• Increases water supply in areas suffering from deficit
• Sale of water helps the economy
• These are a complicated and costly solution because they involve complex systems of canals and pipelines to take water from one river basin to another
• They can lead to wastage in the area receiving water
• In the area giving water there are environmental impacts such as declining fish stocks and increased pollution

Desalinisation

Desalinisation is the process of removing salt from sea water to turn it into fresh water, for drinking and irrigation. Many countries in the Middle East have desalinisation plants, and more recently the USA, Japan and Spain have embraced this solution to increase their water security.

How does it work?

1) Seawater intake - seawater is slowly drawn in from the ocean - a protective grill means that marine life can’t swim into the structure.

2) Infiltration - pre-treatment filters remove solids such as sand and sediment.

3) Reverse osmosis - filtered seawater is pushed through ultra-fine membranes under high pressure. Fresh water will pass through, leaving seawater concentrate behind.

4) Remineralisation - desalinated water has minerals added, to meet government drinking water guidelines and health requirements

5) Storage - drinking water is stored before it is distributed into regional water networks.

6) Water outlet - concentrated sea water is returned to the ocean through diffusers to be diluted by the ocean currents.

(You can see this process in the image below)

Pros and cons

• Increases the amount of water available and can increase water security
• But is very expensive – both the process and the transportation of desalinated water to areas inland - so only suitable for HICs, therefore its impact with increasing global water security has been limited
• Lots of environmental issues, including dumping waste salt back into the sea, requires a lot of energy to complete the process, which means it has a large carbon footprint