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<br />,. <br /> <br />- 9 - <br /> <br />THE NATURE ANO EXTENT OF GROUND-WATER <br />CONTAMINATION OF THE UNITED STATES <br /> <br />EPA's Task Force on Ground Water examined a number of <br />published and internal technical reports to assess the nature, <br />sources, and extent of ground-water contamination. This chapter <br />presents the findings and conclusions of that review, which <br />heavily influenced the policy presented in Chapter IV. <br /> <br />Findinqs <br /> <br />1. THE NATURE OF GROUND WATER <br /> <br />Ground Water is a vast and little understood resource. In <br />fact, it may be one of the least understood of our major natural <br />resources. Many people continue to think of ground water as a <br />series of underground streams or rivers. Rather, ground water <br />is water that occurs in aquifers beneath the surface of the earth. <br />Aquifers are geologic formations--usually consolidated rock--that <br />contain enough water in a sufficiently permeable setting to yield <br />useable amounts of water to wells and springs. <br /> <br />useable aquifers underlie most of theUnited.States. The <br />volume of known ground-water resources is about 50 times greater <br />than annual surface flow in the entire Nation. Another way to <br />conceptualize the immense size of this resource is to consider <br />that the volume of ground water to be found within one-half mile <br />of the surface is estimated to be more than four times that of <br />the Great Lakes. In general, the degree to which people use an <br />aquifer depends on whether good quality surface water is avail- <br />able and on the relative cost of delivering the ground water to <br />individual users. <br /> <br />Ground water provides a substantial orocortion (24%) of the <br />Nation's domestic, agricultural, and industrial wate~. Between <br />1950 and 1980, total ground water withdrawals increa~ed from 34 <br />to 89 billion gallons per day (BGO), an increase of 160 percent. <br />This represents 24 percent of all the fresh water used (372 BGD) <br />in 1980. Further, ground-water withdrawals are projected to <br />reach 100 BGO by 1985. The principal uses of ground water in <br />1980 were for irrigation (60 BGO), supply for public drinking <br />water systems (12 BGO), with smaller amounts applied to industrial <br />and rural household use.l/ <br /> <br />Reliance on ground water, as a. proportion of all fresh <br />water used, has increased greatly over the past 35 years. In <br />part, this increase is the result of a migration of population <br />during the decade of the 1970's to rural areas, where ground <br /> <br />~~..o-r <br />