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Watersheds; Minnesota River Watershed (S.D. and Minn.); Geomorphology


The geomorphology of the Minnesota River Basin is poorly understood, yet much of modern fluvial ecology requires this information as a prerequisite to physical, chemical, or biological studies. The purpose of this paper is to provide background descriptive geomorphological river basin data for the Minnesota River. Eleven descriptive parameters (river gradient, Form f, Shape 1, Shape 2, circularity ratio, elongation ration, stream order, bifurcation ratio, average area by order, number of lakes per order and number of lower order streams entering higher streams) were determined for the Minnesota River Basin as a whole as well as for ten subbasins. A total of 6,188 streams were categorized, with 77% being first order, 18% second order, 4% third order, 1% founh order, 0.3% fifth order and 0.01% sixth order. The Minnesota River itself was determined to be a seventh order stream. A bifurcation ratio of3.8 for the entire Minnesota River was found to be consistent with an earlier prediction of 3.5 for the average basin. The streams that run off the Coteau des Prairies were found to have a smaller drainage basin per order of stream than the Blue Eanh, Chippewa and Pomme de Terre rivers. No difference was found among the subdivisions of the Minnesota River in the number of lower order streams entering higher order streams. Of the remaining descriptive parameters only two, Shape 2 and river gradient, showed any noticeable difference among basins. The river gradient is higher in the Coteau des Prairies than in other streams in the Minnesota Basin. The Blue Earth and Pomme de Terre River basins had different values from the mean for Shape 2. The Pomme de Terre River Basin had high value, meaning it is a long and narrow basin. The Blue Earth River Basin had a low value, meaning its basin is wider than it is long. The two most notable findings were, first, that the Minnesota River is a seventh order river for most of its length beginning at the junction of the Yellow Bank and the mainstem. Secondly, even though Big Stone Lake is considered as the source of the Minnesota River for geopolitical reasons, this study indicates the source of the Minnesota River is the Little Minnesota River, because it is already a fifth order river when it enters Big Stone Lake and drains 1,157 square kilometers.

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