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  3. Fresh Water Shortage A water crisis is about to explode. Fresh water is a finite resource. The amount of fresh water supply

Fresh Water Shortage A water crisis is about to explode. Fresh water is a finite resource. The amount of fresh water supply

admin2010-04-30  36
问题                                       Fresh Water Shortage
    A water crisis is about to explode. Fresh water is a finite resource. The amount of fresh water supply provided by the hydrological cycle does not increase. Water everywhere on the planet is an integral part of the global hydrologic cycle. Precipitation (降水) originates as evaporation from land and the oceans. Soil moisture is used by plants, which return more moisture to the atmosphere, which then returns to the Earth as rain or snow. Barlow and Clark add, "Unless we dramatically change our ways, between one-half and two-thirds of humanity will be living with severe freshwater shortages within the next quarter-century."
    Humans share the Earth with other creatures who also need water, therefore, a water shortage is also a crisis for wildlife. Of the 25-biodiversity hot spots designated by Conservation International, 10 are located in water-short regions.
Fresh Water in Man’s Life
Seventy percent of all the fresh water is used for irrigation.
    •  Agriculture uses the largest amount of freshwater (70%).
    •  Forty percent of the world grain harvest is produced on irrigated land, therefore, a water shortage will become a food shortage.
    •  Countries are importing grain as a way to import water. It takes 1,000 tons of water to grow one ton of grain. On the other hand, exporters of grain are exporting water. (The U.S. annual grain exports of 90 million tons of grain represent 90 billion tons of water, an amount that exceeds the 67-billion-ton annual flow of the Missouri River. )
    •  Producing one ton of grain requires 1,000 tons of water, but producing one ton of beef requires 15,000 tons of water (and nearly that much is required to produce a ton of cotton). Producing wheat or soybeans requires only 2% of the water required by beef.
Twenty percent of fresh water is used by industry.
    As water becomes scarce, demand for water in cities and by industry is satisfied by taking water from a country’s agriculture, with imported grain offsetting the shortfall. Conservation programs are not applied to industry.
Ten percent of fresh water is used for residential purposes.
    Residential use accounts for 10 percent of fresh water use and about three-fourths of the urban water demand. Each day in the U.S., more than 4.8 billion gallons of drinking water is flushed down toilets.
    Showers account for about 20 percent of total indoor water use. The EPA says that by replacing standard 4.5-gallon-per-minute showerheads with 2.5-gallon-per-minute heads, which cost less than $5 each, a family of four can save approximately 20,000 gallons of water per year. Outdoor residential water use varies greatly, but on average, nationally, lawn care accounts for about 32 percent of the total residential outdoor use. Other outdoor uses include washing automobiles, maintaining swimming pools, and cleaning sidewalks and driveways.
Signs of Stress as the Demand for Fresh Water
Rivers are running dry.
    Many major rivers—including the Colorado, Ganges, Indus, Rio Grande, and Yellow—are so over-tapped that they now run dry for part of the year. Freshwater wetlands have shrunk by about half worldwide. In 1972, the Yellow River in China failed to reach the sea for the first time in history. That year it failed on 15 days; every year since, it has run dry for a longer period of time, until in 1997, it failed to reach the sea for more than half a year.
Water tables are falling on every continent.
    Aquifer (蓄水池) depletion is a new problem. Water tables are falling from the overpumping of groundwater in large portions of China, India, Iran, Mexico, the Middle East, North Africa, Saudi Arabia, and the United States. India has the highest volume of annual groundwater overdraft of any nation in the world. In most parts of the country, water mining is taking place at twice the rate of natural recharge, causing aquifer water tables to drop by 3 to 10 feet per year. This enormous shift from sustainable water use to over-mining began when farmers changed from having oxen withdraw the water from a well, to using electric or diesel-driven (柴油机发动的 ) motors.
Causes of Fresh Water Shortage
Global Warming
    Some scientists say that global warming is the single greatest cause of the fresh water shortage in the world. A rise in average temperature in mountainous regions can alter the precipitation mix between rainfall and snowfall, with more rain and less snow. This change means more flooding and more runoff during the rainy season, but also less water held as snow and ice in the mountains for use in the dry season. These mountain glaciers or "reservoirs in the sky" are all melting. The snow/ice mass in the Himalayas, (the third largest in the world, after the two polar ice caps) is now beginning to shrink at an accelerating rate. Every major river in Asia originates in that snow/ice mass.
Privatization of Water
    In our economic system, "scarcity creates value", so many corporations are trying to privatize access to water. To facilitate this, corporations want water officially designated as a need, rather than a right. If water is only a "need", the private sector, through the market, could provide this resource on a for-profit basis. If water is officially recognized as a universal right, governments would be responsible for ensuring that all people would have equal access on a nonprofit basis.
    Corporations are using the World Trade Organization to force Third World countries to privatize water markets and grant corporations access to them. The World Bank has made privatization of urban water systems a condition for receiving new loans and debt restructuring. There are places where people are resisting this trend to privatization of water. In August 2002, the Nicaraguan National Assembly became the first parliament in the world to suspend private profit making in the use of water.
    Commercial water export would only perpetuate (长期化) the basic problem that has caused the "water crisis" in the first place: responding to people’s growing demands for water by increasing supply. This demand has led to the draining of lakes, the depletion of aquifers and destruction of aquatic ecosystems around the world. Pollution of Fresh Water
    In addition to our using more water than is returned in rain, we are also polluting the water we have. Most of the pesticides and fertilizers used in agriculture, sewer overflows, and the oil and grease from roads, eventually run off into the water systems. Other sources of excess nutrients include lawn fertilizers, pet and farm animal waste, decaying plant material, failing septic tanks, and inefficient sewage treatment plants. Industrial plants and municipal wastewater treatment plants can also contribute to the amount of toxic substances entering streams and rivers and ultimately lakes, estuaries (河口), and coastal waters.
    More than 60 percent of U.S. coastal rivers and bays are moderately to severely degraded by nutrient runoff. Every eight months, nearly 11 million gallons of oil run off our streets and driveways into our waters—the equivalent of the Exxon Valdez oil spill. Water sheds, inland forests, agricultural areas, and population centers are the source of about 80% of marine pollution. This runoff creates harmful algae (藻类) blooms and leads to the degradation or loss of seagrass and kelp beds as well as coral reefs, all of which are important for spawning (产卵) and nursery grounds for fish.
    Large-scale farms which mass-produce animals, confining them in crowded feedlots (动物养殖场) and factory-style barns, create massive amounts of pollution. According to the EPA, U.S. animal feedlots produce about 500 million tons of manure each year, more than three times the amount of human waste. This animal waste, (with antibiotics) also ends up in groundwater and surface water in huge quantities.
    The expanding loss of wetlands means these runoff nutrients aren’t processed and purified by nature before they enter rivers, streams, and ultimately estuaries. The rainfall on the European continent is so full of toxic pesticides that much of it is too dangerous to drink.
Some Solutions
    There are solutions: better public and community control of water utilities; repairing old water systems, using less water for agriculture by using drip irrigation, stopping polluting the water we do have, increasing water conservation and focusing resources on watershed management.
According to some scientists,______is the single greatest cause of the fresh water shortage in the world.
选项
答案global warming
解析
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