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<br />
<br />N
<br />
<br />Effects of Irrigation Development
<br />on the Interaction of
<br />Ground Water and Surface Water
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<br />Nebraska ranks second among the States with respect
<br />to the area of irrigated acreage and the quantity of water used
<br />for irrigation. The irrigation water is derived from extensive
<br />supply systems that use both surface water and ground water
<br />(Figure N-l). Hydrologic conditions in different parts of
<br />Nebraska provide a number of examples of the broad-scale
<br />effects of irrigation development on the interactions of ground
<br />water and surface water. As would be expected, irrigation
<br />systems based on surface water are always located near
<br />streams. In general, these streams are perennial and (or)
<br />have significant flow for at least part of the year. In contrast,
<br />irrigation systems based on ground water can be located
<br />nearly anywhere that has an adequate ground-water
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<br />EXPLANATiON
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<br />o SurfaCEl-water
<br />irrigation project
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<br />resource. Areas of significant rise and decline in ground-water
<br />levels due to irrigation systems are shown in Figure N-2.
<br />Ground-water levels rise in some areas irrigated with surface
<br />water and decline in some areas irrigated with ground water.
<br />Rises in ground-water levels near streams result in increased
<br />ground-water inflow to gaining streams or decreased flow
<br />from the stream to ground water for losing streams. In some
<br />areas, it is possible that a stream that was losing water before
<br />development of irrigation could become a gaining stream
<br />following irrigation. This effect of surface-water irrigation prob-
<br />ably caused the rises in ground-water levels in areas F and G
<br />in south-central Nebraska (Figure N-2).
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<br />Figure N-1. Nebraska is one of the most extensively irrigated States in the Nation. The irrigation water comes from
<br />both ground-water and surface-water sources. Dots are irrigation wells. (Map provided by the University of Nebraska,
<br />Conservation and Survey Division.)
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<br />58
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