文档介绍：2017年***英语三级考试阅读理解****题讲解9
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America is in no immediate danger of "running out of water". People in the West have been aware that water is a precious commodity and must be conserved. In the damp East, an excess of water led to complacency until two factors created concern over our water supply. First, the periods of drought from the 1961 to 1966 in the Northeast affected crop production and used up the surface and ground water supplies. Second, attention was called to rapid increases in the rates of pollution of these waters resulting from increased urban and industrial growth. As a result, there is an increasing awareness of the need for conserving the quantity and quality of our nation's water supplies.
Water is a renewable resource, but it is not exhaustible. When used for municipal, industrial, or agricultural purposes, it is not destroyed, but generally finds its way back into our water supply. This used water now carries some waste materials. These dirty waters are often dumped into large bodies of water or are disposed of on land. In the latter instance, evaporation concentrates some of the wastes on the soil surface. On the other hand, water moving through the soil will eventually carry some of the wastes down into the ground water supplies, Eventually, all water evaporates and later returns to the earth as rain or snow in a relative