问答题

Water Problems Where’’s the water Water. If you’’ve got it, you probably take it for granted. But a quick look at the globe — and a chat with the tiny group of researchers who are worrying about fresh water — both indicate that water shortages are very serious. And they aren’’t necessarily in the future, either. Here’’s what we’’ve read in the past week or so. ... Mexico City (home to 20 million people) is sinking because the city sucks out underground water faster than the aquifer can be refilled. ... Florida wants to refill its overpumped aquifer (蓄水层) with untreated surface water, despite federal regulations to the contrary. ... Texas is moving toward private, for-profit water sales. The water will be "mined" from aquifers that are disappearing fast. No word on what the private suppliers, including corporate raider T. Boone Pickens, will do once the aquifers run dry. ... Aquifers around the world are being overtapped for irrigated agriculture, which fills about 40 percent of the global larder. ... The Bush Administration has withdrawn a proposed tightening of the arsenic standard for drinking water. Critics say the old rule, dating to 1942, could allow thousands of cases of cancer and other diseases. Meanwhile, in Bangladesh, what’’s been called the "largest poisoning of a population in history" has 35 to 77 million people drinking arsenic-laced water. ... A showdown is looming over the Tigris (底格里斯河) and Euphrates Rivers (幼发拉底河), which originate in Turkey, then water both Syria and Iraq. If Turkey goes ahead with a series of dams, the downriver nations could starve. You don’’t miss your water, an old blues sage wisely said, until your well runs dry. Down here on planet Earth, the well is starting to run dry. We’’ ve seen projections that three billion people —half of today’’s population — will be short of water in 2025. Places short of water Seen from a global water map, water is shortest in equatorial countries, often where populations are rising. Here are some examples of countries facing water shortage problem. China, with 1.26 billion people, is "the one area worrying most people most of the time," says Marq de Villiers, author of the recently published "Water ". In dry Northern China, he says, "the water table is dropping one meter per year due to overpumping, and the Chinese admit that 300 cities are running short. They are diverting water from agriculture and farmers are going out of business." Some Chinese rivers are so polluted with heavy metals that they can’’t be used for irrigation, he adds. "They’’ re disgraceful, unusable, industrial sewers," says de Villiers. As farmers go out of business, China will have to import more food. In India, home to 1.002 billion people, key aquifers are being overpumped, and the soil is growing saltier through contamination with irrigation water. Irrigation was a key to increasing food production in India during the green revolution, and as the population surges toward a projected 1.363 billion in 2025, its crops will continue to depend on clean water and clean soil. Israel (population 6.2 million), invented many water-conserving technologies, but water withdrawals still exceed resupply. Overpumping of aquifers along the coast is allowing seawater to pollute drinking water. Like neighboring Jordan, Israel is largely dependent on the Jordan River for fresh water. Water Fight Egypt, whose population of 68 million may reach 97 million by 2025, gets essentially no rainfall. All agriculture is irrigated by seasonal floods from the Nile River, and from water stored behind the Aswan High Dam. Any interference with water flow by Sudan or Ethiopia could starve Egypt. "The Nile is one I worry about," says Sandra Postel, director of the Global Water Policy Project. Egypt, she says, is militarily powerful but vulnerable. "The hydropolitics might favor some military action, because Egypt is so heavily dependent on the Nile, it’’s already virtually tapping out the supply, and Ethiopia is now getting interested in developing the headwaters." When a World Bank official suggested several years ago that water wars are not far off, he might have had Egypt on his mind — or Turkey, Syria and Iraq, another trio of Middle-Eastern states that are locked in an uncomfortable embrace over water. The Tigris and Euphrates Rivers both rise in Turkey and flow unimpeded to Syria and Iraq, where they provide the bulk of irrigation water needed in the arid climate. Turkey has proposed a series of dams that would reduce river flow. That causes alarm downstream. Cooperation on water Despite the potential for fights over water, shortages can increase cooperation as well as friction. Jordan and Israel closely cooperate on the preservation of the Jordan River. Author de Villiers says water shortages, rather than exacerbating tensions in the Middle East, "have brought them together" — although we wouldn’’t overstate the degree of cooperation. Egypt stores a great amount of Nile water behind the Aswan High Dam, but the high rate of evaporation in the desert is an incentive to transfer the storage upstream, where, according to Postel, it would evaporate one-third as fast. Although that would leave more water to be shared, Egypt would never allow Ethiopia to build dams without assurances of a steady water supply in drought years. Although there’’s no agreement yet, there’’s been some cooperation, Postel says. "Ethiopia and Egypt meet about water every year, trying to work toward a watersharing arrangement — something they would not have considered 10 years ago." There are other reasons for optimism about the generally dismal water situation. For example, total U.S. usage has dropped 20 percent from a peak in 1980. De Villiers says some underdeveloped countries are likewise reducing consumption. "Namibia is famously thrifty for its use of water [in dry years, up to 30 percent of the capital’’s drinking water is recycled wastewater]. Egypt recycles virtually everything they get." And while rivers are heavily polluted in China and elsewhere, a few rivers are being restored. De Villiers says the Rhine, once called the sewer of Europe, has been cleaned up over the past decade or so. ’’T d not want to drink it, but fish are reappearing in the river." Can technology help Because water is generally used so inefficiently, Postel calls conservation "the last oasis." Simple devices like low-flow toilets can cut usage by 70 percent. When New York City was faced with spending $1 billion on a new pumping station in the early 1990s, it opted instead to replace toilets. By 1997, after the city spent $295 million on incentives, 1.33 million new toilets had been installed, saving 70 million to 90 million gallons per day. Overall, per capita consumption dropped from 195 gallons in 1991 to 169 gallons in 1999. Agriculture, which uses about 70 percent of total fresh water, offers much larger savings. Drip irrigation, pioneered by Israel, delivers water directly to the crops roots. Although it’’s more expensive to start with, it’’s far more frugal as well in terms of water. And delivering water steadily to the roots improves production as well. Postel writes, "Studies in India, Israel, Jordan, Spain and the U.S. have shown time and again that drip irrigation reduces water use by 30 to 70 percent and increases crop yield by 20 to 90 percent compared with flooding methods." Reuse of wastewater is becoming a fact of life in many arid regions, including Egypt, Israel, and the American Southwest. Depending on its cleanliness, water may be used to irrigate non-food crops, or even food crops. In the extreme example, Namibia, as we’’ve seen, drinks treated wastewater in drought years. Desalination — the removal of salt from salt water — would be the ultimate solution to water woes — if it can be done cheaply enough. That’’s a big if: "The best estimates are $2 to $2.50 per ton for desalination," says de Villiers. "That not really that far from the real cost of delivering water from the Colorado River, but California’’s water is so heavily subsidized that they are paying 10 cents per ton when the real cost is closer to $2.50 per ton." Desalination also takes a lot of electricity, de Villiers notes. "Unless somebody comes up with a way to do it with less energy," the cost of more fresh water could be increased global warming. Drip irrigation is a way of delivering water directly to_________.