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<br /> <br /> <br />- <br /> <br />- -.,' <br />, ,_ !II!: <br />~-- c.':--- <br /> <br />land irrigated by using ground-water center-pivot <br />sprinklers In Nebraska. (Photograph by les Sheffield.) <br /> <br /> <br />Average annual precipitation ranges from less than <br />15 inches in western Nebraska to more than 30 inches in <br />eastern Nebraska. A large concentration of irrigation wells is <br />present in area E (Figure N-2). The ground-water withdrawals <br />by these wells caused declines in ground-water levels that <br />could not be offset by recharge from precipitation and the <br />presence of nearby flowing streams. In this area, the with- <br />drawals cause decreases in ground-water discharge to the <br />streams and (or) induce flow from the streams to shallow <br />ground water. In contrast. the density of irrigation wells in <br />areas A. B, and C is less than in area E, but water-level <br />declines in these three western areas are similar to area E. <br />The similar decline caused by fewer wells in the west <br />compared to the east is related to less precipitation, less <br />ground-water recharge, and less streamflow available for <br />seepage to ground water. <br /> <br />,~ <br /> ..... l~' KoI"'P:t<l <br />l~A o- w, <br />~ ... D <br />, . <br /> ...,. <br /> ^l'~ . <br /> "'l <br /> """ - .... '" <br />Scol\s!l.tl ..."... <br />- ''''' <br /> '"". <br />.... "'_ <br />EXPLANATION <br />- > +SO-foot rise <br />lIIil +20 to +50 <br />= +10 to +20 <br />= -5to+10 C <br />= -5to-10 .- ~od .....", ..... ..... <br />= -10to-15 <br />= -15to-20 <br />= -20to-25 <br />= -25to-30 0 20 40 MILES <br />- > -3D-foot decline I I I <br /> <br /> <br />Ffgure N-2. The use of both ground water and surface water for irrigation in Nebraska has resulted in significant rises and <br />declines of ground-water levels in different parts of the State. (Map provided by the University of Nebraska, Conservation <br />and Survey Division.) <br /> <br />59 <br />