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<br /> <br />Mississippi River above St. Louis, Missouri. Tributaries include <br />the Milk, Yellowstone, Little Missouri, Cheyenne, Niobrara, <br />James, Big Sioux, Platte, Kansas, Grand, and Osage Rivers. The <br />three major physiographic divisions within the Basin are the <br />Rocky Mountain System, the Interior Plains, and the Interior <br />Highlands. The Rocky Mountain System is an area of exceptionally <br />rugged topography with deep stream valleys, high plateaus, clear <br />alpine lakes, and high mountain peaks. Cold water streams in <br />this area provide high quality fishery habitat. The vegetation <br />varies from alpine tundra and coniferous forests in the higher <br />elevations to brushlands and grasslands in the intermountain <br />valleys. The Interior Plains range from flat to rolling or hilly <br />topography which was originally dominated by grassland <br />vegetation. This area is dissected by intermittent or perennial <br />warm water streams and rivers. The fishery habitat of these <br />waters varies from good to poor depending upon water flows, <br />substrate, chemical characteristics, and numerous other <br />parameters. Riparian woodlands have developed along these <br />streams where ecological conditions have been favorable. The <br />Interior Highlands is topographically diverse and dissected by <br />many productive warm water streams. The vegetation is also <br />diverse and in its natural state was dominated by the eastern <br />deciduous forest. <br /> <br />Approximately 298 million acres or 92 percent of all the <br />land in the Basin is used for agricultural purposes. More than <br />half of the agricultural land is used for pasture and rangeland. <br />Irrigated cropland comprises 11.4 million acres or about 4 <br />percent of the present agricultural total with irrigated acreage <br />expected to increase approximately 50 percent by the year 2000. <br /> <br />The economy of the Basin has historically been dominated by <br />agriculture, but the region has also produced metallic and <br />precious minerals, timber products, fuel products, and electric <br />power. Recently, substantial increases in mining, manufacturing, <br />and recreation-tourism have served to further strengthen and <br />diversify the economic activities. <br /> <br />While the Missouri River Basin has an overall adequate <br />supply of surface and ground water resources, distribution of <br />this water in space and time often does not meet local or <br />regional demand. Hence, seasonal shortages occur in several <br />areas. In addition, the quality of the water resources is highly <br />variable, which aggravates the water supply problem for many <br />users. <br /> <br />-252- <br />