Upper Mississippi River System

Recent proposals to expand the Upper Mississippi River Illinois Waterway (UMR-IWW) ? a major transportation route for products moving to and from Illinois, Iowa, Minnesota, Missouri, and Wisconsin ? have met with significant controversy. Some of this controversy centers on the cumulative environmental effects of the current navigation system and the proposed expansion. The Upper Mississippi River System (UMRS) ? which includes the navigation channel and surrounding floodplain ? supports an unusually large number of species for a temperate river. The UMR-IWW navigation system alters UMRS habitat and contributes to a decline in the abundance of some species. For example, locks, dams, and other channel structures inhibit the movement of fish between and within river segments; fill side channels, backwaters, and wetlands with sediment; and suppress plant growth by reducing water clarity.