Water transfer is the transfer of water from one river catchment to another. Transfer can take place by river diversion, pipeline or even by sea tanker. There is often a surplus of water in one area and too little in another - both on a small scale within a country, on a larger, continental scale and even on a global scale. Water transfer is one method of increasing the supply to areas with too little water.
For example, Manchester is supplied with water piped from reservoirs in the Lake District and the industrial cities of South Yorkshire are supplied with water from rivers to the north through the Yorkshire Grid Scheme, which uses rivers and large mains to transfer water from one river catchment area to another.
The Snowy Mountains Scheme
One of the world’s largest-scale national water transfer schemes in existence is the Snowy Mountains Scheme in Australia, where water is lacking in the vast, low-lying interior, but the eastern rim of highlands has plentiful rainfall. Unfortunately the rivers of the highlands flow eastward into the Pacific Ocean mainly unused. The Snowy Mountains Scheme traps part of the flow of two of these rivers in reservoirs.
This water is then pumped through tunnels and aqueducts to the west side of the Snowy Mountains, to the Murray and Tumut River systems, increasing the water available to Australia’s interior. Because of the difference in altitude between the intake in the highlands and the outlet in the interior, the Scheme generates enough hydroelectricity to pay for the operating costs.
The Scheme was completed in 1974, taking 25 years to build, at a cost of £400 million. It diverts an average of 2.36 × 109 m3 of water a year to the interior, and the hydroelectric power output is 3754 MW (equivalent to the power output of almost four nuclear power stations). The system has the flexibility to allow water to be released from reservoirs only when needed during the dry season, or to allow water to be transferred between reservoirs.
Although the discharge of the Murray and Tumut Rivers was successfully increased, there have been large environmental impacts associated with the scheme such as:
land drowned by reservoirs,
higher water tables,
increased leaching of salts into rivers, and
ecological changes in the river basins.
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