8 - Upper Mississippi River Basin

Abstract

The Upper Mississippi River basin drains Lake Itasca in the bog and spruce swamps of northern Minnesota and flows south to join the Ohio River as a 10th order alluvial river to form the largest river in North America. The progression of the river from the lake outlet to the great river creates an impressive range of physical, chemical, and biological diversity throughout the basin. The basin encompasses five terrestrial ecoregions, three biomes, and three physiographic provinces. Despite the variability created by climate and geology, commonalities are evident among rivers at the physiographic province and terrestrial ecoregion levels. Climatic conditions change considerably from the northern extreme of the basin to its southern boundary at the confluence with the Ohio River. This chapter presents the rivers acting as a representative within each region and that reflect both the common threads among rivers in the Upper Mississippi River basin and their unique attributes. The Upper Mississippi River is the only bioregionally outstanding river. This is partly due to the fact that there is only one species of fish, one species of crayfish, and one freshwater mussel, which are endemic to the region.