GCSE Geography | Water Supply in the Western Desert (Hot Deserts 7)

Large-scale water transfers from the Colorado River have enabled tourism and farming to prosper in the Western Desert - however in recent years rapid population growth has led to a water crisis.

Supplying the Western Desert with water

The Colorado River is huge, travelling 2,300 km and brings meltwater from the Rocky Mountains into the Western Desert.

Indigenous populations drew water from the river through a series of small dug canals, which they used to irrigate their crops. However, the water supply is unreliable. River discharge is high in the summer due to snowmelt, but the flow is extremely low between September and April, which is problematic for farming.

The Hoover Dam was constructed in the 1930s, with Lake Mead (a reservoir) behind it, which can store two years worth of river flow behind it. In the 1960s the Glen Canyon Dam was built. These two dams and the reservoir control the river flow, preventing periods of flooding and drought. Water is piped from Lake Mead along a series of aqueducts to be used for domestic and agricultural uses, as well as to water the many golf courses of the Western Desert, and provide water for all the luxury hotels in Las Vegas.

Transferring water across the Western Desert has bought many advantages and disadvantages.

Advantages of transferring water across the Western Desert

• Cities such as Phoenix, Las Vegas and San Diego are supplied with water.
• Irrigation enables 1.5 million acres of land to be farmed with fruit and vegetable crops, as well as livestock grazing. This region produces approximately 1/5 of the USA's crops, and 1/6 of the USA's livestock - and contributes around US$2 billion per year to the US economy.

Disadvantages of transferring water across the Western Desert

• The dams trap silt and sand which builds up behind the dam - this has an impact on marine wildlife as it changes water temperature, which many species can't adapt to. This is because sunlight heats up silt, which warms the surrounding water. The water in the reservoir behind the dam is much deeper than the main river - and as a result is much colder.
• The trapped silt and sand means that river banks have been starved of sediment, so the sandbanks are much smaller, which has had an impact on river habitats, and has made fishing along the banks more difficult.

The future of the Western Desert

More than 30 million people depend on water from the Colorado River. Cities are only allowed to take a certain amount of water - this is because if they take too much the river will dry up, but also their is a political agreement with Mexico that states water must be allowed to flow into the country (where the mouth of the Colorado River is).

Many cities in the region already extract the maximum amount of water allowed, but many of them are predicted to see their populations double in size by 2050 meaning that water insecurity in the future will be a huge issue.

This will be exacerbated by climate change - scientists predict that areas of existing water scarcity will see reduced precipitation, and desert areas are expected to warm faster than the rest of the world.