Different strategies can be used to increase water supply.
The World has enough water for everyone, but its availability varies from place to place and time to time. Richer High Income Countries (HICs) have greater ability to increase water supply, either by purifying and cleaning water or trapping and transferring it. Many water projects are huge in scale and have various economic, social and economic impacts. These projects involve high levels of engineering skill and resources, and include dams and reservoirs, water transfers and desalination. More sustainable solutions are also possible that are smaller in scale, less expensive and can be maintained by local people.
Dams and reservoirs
One way in which we manage water supply is to build huge concrete and steel structures called dams. These dams block rivers and cause the water carried by rivers to back up and flood the valley upstream of the dam creating a large lake known as a reservoir. This water can then be used or released through the dam to produce Hydro Electric Power (HEP).
By building a dam it allows engineers to control the flow of a river - this can therefore be used store water during wet periods for use at times of water shortage. Newcastle upon Tyne gets some of its water from Kielder Water dam and reservoir, and China has just completed construction of the World's largest dam at 3 Gorges. This dam has reduced the risk of flooding downstream of the dam from one in 10 years to one in a 100. Recent flooding prior to dam construction affected millions of people and ruined farmland because of clay that was deposited on the fields. The dam will protect over 25,000ha of farmland. The dam has a huge series of locks running up one side to aid navigation, and will generate huge amounts of electricity. However, 1.4 million people had to be displaced (moved) to make way for the 600km lake that has formed behind the dam, there are expected to be problems with the huge amounts of sediment that will be deposited behind the dam and waste has been a problem. The city of Chongqing puts around 1 billion tonnes of untreated waste into the lake very year.
Dams can be very expensive as they are huge engineering projects that require vast financial resources. For example, the construction of the Itaipu Dam on the border of Brazil and Paraguay (completed in 1984) cost around US$20 billion. People can also be displaced by the dam site and the reservoirs that accumulate behind, and many ecosystems are destroyed too.
1. There are over 50,000 Large Dams with a height of 15 meters or more, most were built after World War II.
2. Dams have flooded a land area the size of Spain. Their reservoirs contain three times as much water as all the world's rivers, and constantly lose close to four Niagara Falls to evaporation.
3. Dams generate 16% of the world's electricity and irrigate food crops for 12-15% of the world's population
4. Dams block the migration of fish, deplete rivers of oxygen, and interfere with the biological triggers that guide fish. They also reduce the ability of rivers to clean themselves. Due to dam building and other factors, Freshwater species have lost 76% of their populations since 1970 – twice the loss which marine and terrestrial ecosystems have suffered.
Diversion or water transfer schemes simply move water from an area of surplus in a country to one which has a deficit. This can take place either through gravity systems or using large pumping stations, and moved about in canals and pipes. The Romans used aqueducts to move water around the Mediterranean like the Pont du Gard (see below), whilst modern systems tend to use pipes. On page 10 you can read about the Kielder water transfer scheme which operates in the UK. This scheme is a local scheme within the same river basin, however bigger scheme schemes include the Tagus Segura project in Spain and the South-North Water Transfer Project (SNWTP) in China.
By Benh LIEU SONG (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Desalination is removing salt and other minerals to create fresh, drinkable water. Desalination is used where fresh water supplies are short but seawater is plentiful, to supply a community with fresh water for households, manufacturing or agriculture. In the past, desalination was deemed too expensive to be considered a viable large-scale option; it simply required too much energy. But newer technologies have slowly started to change that opinion, especially in places where sources of freshwater are scarce, and people are plentiful. This means that at present desalinisation remains a process available only to the wealthiest of countries.
Countries who are treating seawater include Japan, Australia, Spain and a clutch of Middle Eastern States such as the UAE, Saudi Arabia and Kuwait. Australia has spent $13 billion on desalinisation plants for 5 of its major cities to provide up to 30% of their water in the future (source).
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