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<br />shows the Jveri.lge freeze-free period fur the basin which. <br />for the nonmountainous area, ranges from about 90 to <br />180 days_ <br />Mean total hours of sunshine annually :lfe favorable <br />for agriculture and healthful environment, ranging from <br />undrr 2400 to 3200 hours, or more, as illustrated by <br />figure 8_ <br /> <br />FIGURE 7 <br />MEAN LENGTH OF FREEZE-FluE PERIOD (DAYSI <br /> <br />LEGEND <br /> <br /> <br />OUIDE'JO <br />CJ,o...~o <br />010..10 <br />_10.120 <br />_110_I~O <br />_r!>O.'1O <br />.0'Ellto <br /> <br />FIGURE 8 <br />MEAN TOTAL HOURS OF SUNSHINE (ANNUALI <br /> <br />LEGelO <br /> <br /> <br />CJUIO[12~00 <br />c::J H~:ll.~ <br />_l~OO-llao <br />_1800-1000 <br />_Jooo.lloo <br />.on.noo <br /> <br />Winds in the basin Ure the rule rather than the <br />exception, particularly in the plains area. Average wind <br />velocities of 10 miles per hour are prevalent oYer much <br />of the basin. In the plains area strong winds accom- <br />panied by snow sometimes create "blizzard" conditions <br />dangerous to bolh mall and livestock_ High winds <br />occasionally prevail during periods of high temperatures <br />and deficient moisture that can destroy crops and <br />desiccate rangeland within a few days. Parts of the basin, <br />particularly the south and east, are subject to cyclonic <br /> <br />14 <br /> <br />and tornadic winds that occasionally do considerable <br />damage. <br />Most of the climatic forces are not amenable to <br />change, bur modern technology has done much to <br />enable man to better cope with the extremes that affect <br />his environment and culture. Spec-ial farm and range <br />conservation practices, irrigation, and air conditioning in <br />homes iJnd factories are examples. Generalizations of the <br />basin's dimate, however. are not always applicable to <br />specific areas or to their seasonal advantages. Many <br />people are attracted to parts of the basin because of the <br />favorable climate, and particularly the cool, dry, crisp <br />days of summer are a tourist attraction in the western <br />and orher mountainous areas, and in the Ozarks. <br /> <br />STUDY AREAS <br /> <br />Water and related land resources planning. of <br />necessity, must be iJssociated with manageable sources <br />and use~ of the water supply. For purposes of this study <br />the Missouri River Basin wirhin the United States is <br />divided into eight subbasins representing hydrologic <br />are3S drained by designated major tributaries or groups <br />of tributaries of the Missouri River and including certain <br />closed-drainage basins. The eight designated subbasins <br />are shown in figure 9, and their areas and nomenclature <br />are lisled in table L Throughout the report the <br />short.form designation shown for each subbasin is the <br />commonly used reference. <br /> <br />Table 1 - SUBBASIN STUDY AREAS, <br />MISSOURI RIVER BASIN <br /> <br />SUbbasin (and !!i1.ort-Fonn Designation) <br />Upper Missouri River Tributaries (Upper Missouri) <br />Yellowstone River (Yellow:>tone) <br />Western Dakota Tributaries (Western Dakota) <br />Eastern Dakota Tributarie.~ (Eastern Dakota) <br />Platte-Niobrara River:> (Platte-Niobrara) <br />Middle Missouri River Tributaries (Middle. Missouri) <br />Kansas River (Kansas) <br />lower Missouri River Tributaries (Lower Missouri) <br />Missouri Basin (in United States) <br />Drainage in Canada <br />Missouri River Basin (Missouri Basin) <br /> <br />Area in <br />Square <br />Miles <br />82,755 <br />70,622 <br />77 ,119 <br />58,288 <br />99,492 <br />24,602 <br />60.744 <br />39,673 <br />513,295 <br />9,715 <br />523.0101 <br /> <br />I Excludes 6,340 square miles in the Great Divide (Red Desert) <br />Basin and other noncontributing areas near the basin <br />boundary not included in the land inventory. <br /> <br />While water management must be associated with <br />hydrologically defined areas, the resource planning <br />effort is concerned~also with socio-economic considera- <br />tions. Socio.economic data are available only for <br />politically defined counties and Standard Metropolitan <br />Statistical Areas. Seldom do county boundaries conform <br />to hydrologic boundaries. The basjn or region, therefore, <br />