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Water woes(災(zāi)難) may seem remote to people living in rich countries like the United States. But Americans could face serious water shortages, too especially in areas that rely on groundwater. Groundwater accumulates in aquifers (地下蓄水層)，layers of sand and gravel that lie between soil and bedrock. (For every liter of surface water, more than 90 liters are hidden underground.) Although the United States has large aquifers, farmers, ranchers, and cities are tapping many of them for water faster than nature can replenish(補充) it. In northwest Texas, for example, overpumping has shrunk groundwater supplies by 25 percent, according to Postel.
Americans may face even more urgent problems from pollution. Drinking water in the United States is generally safe and meets high standards. Nevertheless, one in five Americans every day unknowingly drinks tap water contaminated with bacteria and chemical wastes, according to the Environmental Protection Agency. In Milwaukee, 400,000 people fell ill in 1993 after drinking tap water tainted with cryptosporidium (隱孢子蟲)，a microbe (微生物) that causes fever, diarrhea (腹瀉) and vomiting.
THE SOURCE
Where so contaminants come from? In developing countries, people dump raw (未經(jīng)處理的) sewage(污水) into the same streams and rivers from which they draw water for drinking and cooking; about 250 million people a year get sick from water borne (飲水傳染的) diseases.
In developed countries, manufacturers use 100,000 chemical compounds to make a wide range of products.Toxic chemicals pollute water when released untreated into rivers and lakes. (Certain compounds, such as polychlorinated biphenyls (多氯化聯(lián)二苯)，or PCBs, have been banned in the United States.)
But almost everyone contributes to water pollution. People often pour household cleaners, car antifreeze, and paint thinners (稀釋劑) down the drain; all of these contain hazardous chemicals. Scientists studying water in the San Francisco Bay reported in 1996 that 70 percent of the pollutants could be traced to household waste.
Water woes(災(zāi)難) may seem remote to people living in rich countries like the United States. But Americans could face serious water shortages, too especially in areas that rely on groundwater. Groundwater accumulates in aquifers (地下蓄水層)，layers of sand and gravel that lie between soil and bedrock. (For every liter of surface water, more than 90 liters are hidden underground.) Although the United States has large aquifers, farmers, ranchers, and cities are tapping many of them for water faster than nature can replenish(補充) it. In northwest Texas, for example, overpumping has shrunk groundwater supplies by 25 percent, according to Postel.
Americans may face even more urgent problems from pollution. Drinking water in the United States is generally safe and meets high standards. Nevertheless, one in five Americans every day unknowingly drinks tap water contaminated with bacteria and chemical wastes, according to the Environmental Protection Agency. In Milwaukee, 400,000 people fell ill in 1993 after drinking tap water tainted with cryptosporidium (隱孢子蟲)，a microbe (微生物) that causes fever, diarrhea (腹瀉) and vomiting.
THE SOURCE
Where so contaminants come from? In developing countries, people dump raw (未經(jīng)處理的) sewage(污水) into the same streams and rivers from which they draw water for drinking and cooking; about 250 million people a year get sick from water borne (飲水傳染的) diseases.
In developed countries, manufacturers use 100,000 chemical compounds to make a wide range of products.Toxic chemicals pollute water when released untreated into rivers and lakes. (Certain compounds, such as polychlorinated biphenyls (多氯化聯(lián)二苯)，or PCBs, have been banned in the United States.)
But almost everyone contributes to water pollution. People often pour household cleaners, car antifreeze, and paint thinners (稀釋劑) down the drain; all of these contain hazardous chemicals. Scientists studying water in the San Francisco Bay reported in 1996 that 70 percent of the pollutants could be traced to household waste.