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<br />. <br /> <br />. <br /> <br />. <br /> <br />~.~ 0 r; , <br />*.~ .Il.".' <br /> <br />Pro,ject Lands <br /> <br />SURFACE DRAINAGE <br /> <br />The disposal of surface runoff is not a serious problem in the <br />Narrows Unit area. Irrigation losses are usually the only "~ters <br />required to be handled. The natural and man-made drains are adequate <br />for this purpose. In addition to the irrigation losses, however, <br />there is occasionally same storm runoff to be disposed of. Part of <br />this storm runoff originates ,,'ithin the service area, but some consists <br />of foreign waters carried through the service area by tributaries of <br />the river. These tributaries are intermittent streams which range in <br />size from small to large. Occasionally, a storm of high rainfall <br />intensity centers over some of these tributaries and the resulting <br />runoff floods some of the bottom lands along the South Platte River. <br />Usually, the affected lands, if they are otherwise of good quality, <br />are not rendered nonirrigable because of the flooding. However, some <br />lands susceptible to flooding with poor-~uality soils and lmfavorable <br />topography were classed as nonirrigable. <br /> <br />SUBSURFACE DRAINAGE <br /> <br />The irrigable lands for the most part are free of subsurface <br />drainage problems. The soils of 83 percent of the irrigable area <br />were found to be free of stabilized saturated zones, and the porosity <br />is adequate in both the soils and substrata to permit satisfactory <br />drainage under full water supply conditions. <br /> <br />Irrigable lands, amounting to nine percent of the total, have <br />inadequate subsurface drainage to the degree that crop yields are <br />depressed significantly, The studies indicated that the water table <br />level approaches no closer than about 48 inches of the surface for <br />any significant period. The irrigable lands with inadequate subsurface <br />drainage are scattered, but most of thenl occur on low terrace positions. <br />A significant portion of these lands, however, occurs on the uplands <br />in areas that have shale relatively close to the surface. Under future <br />operations with supplemental water, the subsurface drainage is not <br />expected to change significantly on the lands classed as irrigable. <br /> <br />Other irrigable lands, amounting to 7 percent of the total, <br />have drainage restrictions that permit the water table to rise within <br /> <br />59 <br />