Laserfiche WebLink
<br /> <br />feet of water. Infiltration and evaporation deplete a large <br />amount of this naturally occurring moisture. Runoff entering the <br />streams varies widely across the basin, ranging annually from <br />less than an inch in parts of the plains to more than 12 inches <br />in the mountains and the humid southeast. This runoff would <br />account for an average of about 65 million acre-feet of natural <br />flow annually at the mouth of the Missouri River near St. Louis, <br />Missouri, exclusive of evaporation and consumptive uses <br />attributable to water resource project developments. <br /> <br />Under 1970 conditions of development and utilization, the <br />net average annual outflow from the basin was estimated to be <br />53.6 million acre-feet.l Recent appraisals, based upon an <br />aggregation of basin State's estimates of water use, indicate a <br />1975 average annual flow of 49.4 million acre-feet at the mouth <br />of the Missouri River near St. Louis. <br /> <br />Abnormally high and low streamflows are not uncommon in most <br />parts of the basin. Indicative of the drought potential is the <br />fact that natural runoff as low as half the mean has occurred in <br />nearly 10 percent of the years of record. At the other extreme, <br />severe flooding caused by snowmelt, spring rains, and <br />thunderstorms, is common in many drainages throughout the basin. <br /> <br />Surface Water Quality <br /> <br />Overall, the water quality of the basin's waterways can be <br />classed as fair. In the western portions, many of the mountain <br />streams remain pristine and pollution-free in their headwaters. <br />Sediment and dissolved solids concentrations become major <br />problems in the rivers as they flow across the plains. In areas <br />where irrigation is practiced, return flows from croplands are <br />often laden with fertilizers, pesticides, and herbicides, <br />degrading nearby watercourses. Runoff containing high <br />concentrations of organic wastes from animal feedlots is another <br />major agriculture-related water quality problem. Finally, <br />municipal and industrial wastes continue to pollute many of the <br />basin's major and minor streams, although ongoing plans and <br />programs are striving to alleviate many of the problems. <br /> <br />Ground Water Availability <br /> <br />Ground water is the principal water supply source in many <br />areas of the Missouri River Basin. Fortunately, the basin has <br />been endowed with abundant ground water of quality suitable for <br />most purposes. Shallow alluvial deposits are found along most <br /> <br />-26- <br />