Water scarcity looms.
Water scarcity can be physical or economic. Physical water scarcity exists wherever available water is insufficient to meet demand. Economic water scarcity occurs when water is available but inaccessible because of a lack of investment in water provision or poor management and regulation of water resources.
Signs of scarcity are plentiful. Several major rivers, including the Indus, Rio Grande, Colorado, Murray-Darling, and Yellow, no longer reach the sea year-round as a growing share of their waters is claimed for various uses. Water tables are falling as groundwater is overpumped in South Asia, northern China, the Middle East, North Africa, and the southwestern United States, often propping up food production unsustainably The World Bank estimates that some 15 percent of India's food, for example, is produced using water from nonrenewable aquifers. Another sign of scarcity is that desalination, a limited and expensive water supply solution, is on the rise.
Population growth is a major driver of scarcity at the regional and global levels. Locally, pollution reduces the amount of usable water available to farmers, industry, and cities. The World Bank and the government of China have estimated, for instance, that 54 percent of the water in seven main rivers in China is unusable because of pollution. In addition, urbanization and rising incomes tend to increase domestic and industrial demand for water.
In some cases, water scarcity leads to greater dependence on foreign sources of water as shown by countries' "water footprints"--the volume of water used to produce the goods and services, including imports, that people consume. The ratio between the water footprint of a country's imports and its total water footprint yields its water import dependence (see table).
Water Import Dependence, Selected Countries, 1997-2001 Country Water Import Dependence (percent) Netherlands 82 Jordan 73 United Kingdom 70 Japan 64 South Korea 62 Germany 53 Italy 51 France 37 Spain 36 Mexico 30 South Africa 22 Canada 20 Egypt 19 United States 19 Australia 18 Russia 16 Indonesia 10 Brazil 8 Thailand 8 China 7 Argentina 6 Pakistan 5 Bangladesh 3 India 2 Note: Water import dependence is the ration of a country's external water footprint to its total water footprint. Source: Chapagain and Hoekstra, Water International, March 2008.
Climate change is expected to worsen water scarcity globally. By the 2050s, the area subject to greater water stress due to climate change will be twice as large as the area undergoing decreased water stress. Less rainfall is expected in already arid areas, including the Mediterranean Basin, western United States, southern Africa, and northeastern Brazil. Loss of snowpack will remove a natural, off-season water reservoir in many regions: by the 2020s, for example, 41 percent of the water supply to the populous southern California region is likely to be vulnerable to warming as some of the Sierra Nevada and Colorado River basin snowpacks disappear.
Policymakers look to a variety of solutions to address water scarcity. Desalination is increasingly feasible for small-scale water supply, as technological advances reduce costs. Global desalination capacity doubled between 1995 and 2006 and by some forecasts could double again by 2016. But production is tiny: Global capacity in 2005 was some 55.4 million cubic meters, barely 0.003 percent of the world's municipal and industrial water consumption. Forty-seven percent of global capacity in 2006 was in the Middle East, where the need is great and energy is cheap.
Other solutions focus on structural shifts in water use, including growing crops that are less water-intensive, changing dietary patterns to reduce meat consumption, and shifting to renewable sources of energy. Diets heavy in livestock products, for example, are water-intensive because of the huge quantities of water required for livestock production. Similarly, fossil fuel production requires many times more water than renewable energy sources do.
Vital Signs are adapted from Vital Signs Online, which contain additional data and more in-depth analyses.
Visit http://vitalsigns.worldwatch.org to view and read the complete collection of trends.
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|Title Annotation:||VITAL SIGNS|
|Date:||May 1, 2010|
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