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<br />also are marked increases in coliform densities following <br />heavy surface runoff from agricultural and urban areas. <br />There has been no systematic basinwide program for <br />obtaining biologic data or dissolved oxygen data. The <br />available data have been obtained in association with <br />problem areas as discussed in the appendices <br />"Hydrologic Analyses and Projections" and "Present and <br />Future Needs." In general, much more stream quality <br />data arc needed before there can be a realistic evaluation <br />of the many facets of strea.m water quality throughout <br />the Missouri Basin. <br /> <br />Sediment <br /> <br />From the standpoint of erosion characteristics and <br />sediment contributed to streamflow, the Missouri Basin <br />is a diverse area. It varies from flat and nondraining lands <br /> <br />to high mountains; from higWy erodible soil to rock; and <br />from subhumid to semiarid climate. Also, within these <br />general physical diversities there are areas with special <br />localized characteristics. Thus, it is impossible to develop <br />simple formulae for the determination of sediment <br />yields within the basin. <br />It has been necessary to analyze the basin, area by <br />area, considering suspended sediment sampling data, <br />reservoir sedimentation surveys, physiographic and <br />geologic information, soils, topography, climate, runoff, <br />vegetation, land use, upland erosion, channel erosion, <br />and the present knowledge of sediment transport and <br />delivery. With these as a basis it was possible to develop <br />estimates for average annual sediment yield in tons per <br />square mile applicable to drainages in excess of 100 <br />square miles. Figure 30 shows the probable ranges of <br />average annual sediment yield for various areas in the <br />basin. The higher values shown are indicative of the <br /> <br />SEDIMENT YIELD <br /> <br />FIGURE 30 <br /> <br /> <br />~I <br />, <br /> <br />LEGEND <br /> <br />ESTIMATED SEDIMENT YIELD IN TONS <br />PER SQUARE MILE PER YEAR. 400 ~ <br />(DRAINAGES IN EXCESS OF 100 SQUARE MIL~---- ----j. <br />00-000 ~ <br /> <br />o 500 - 1000 <br /> <br />o 1000 ~ 3000 <br /> <br />,. 3000 - 6000 <br /> <br />COLORADO <br /> <br />. 6000+ <br /> <br />66 <br /> <br />~\ <br /> <br />~ <br /> <br />~ <br /> <br />N <br /> <br />t <br /> <br />SCALE 1/11,.500.000 <br />o 10v 200 <br />APPROXIMATE SCALE IN MILES <br /> <br />MINNESOTA <br /> <br />IOWA <br /> <br />KANSAS <br /> <br />g\ <br /> <br />---~r- <br /> <br />, <br /> <br />----{--~?-~-- <br />