Improving Fish Passage Through Navigation Dams on the Upper Mississippi River System
barriers, behavior, channel, design, ecosystems, fish behavior, fish passage, habitat, hydraulic conditions, Mississippi River, navigation locks, swimming, swimming ability
ENV Report 54
U.S. Army Corps of Engineers
Improving fish passage through dams is recognized as an important way to restore river ecosystems. The Upper Mississippi River System (UMRS) has a series of 29 navigation dams on the Mississippi River and 7 navigation dams on the Illinois River. An interagency Fish Passage Team was formed to plan for improving fish passage at the UMRS navigation dams. This report was prepared to provide information for use in the Upper Mississippi River - Illinois Waterway Navigation Study. Of the 143 native fish species in the UMRS, at least 34 species are migratory. The design characteristics and operation of most UMRS navigation dams allow both upriver and downriver fish passage. Downriver fish passage can occur through the locks and the gated sections of the dams. Some of the dams in the system impose complete barriers to upriver fish passage except through the navigation locks. Opportunity for upriver fish passage through the navigation dams depends on hydraulic conditions at the dams, fish behavior, and fish swimming abilities. Operational changes and structural modifications at UMRS navigation dams are possible and may improve opportunity for fish passage throughout the UMRS. Nature-like fishways designed to mimic a natural river channel show the most promise as fish passage improvements on the UMRS. Improved access to habitats should benefit fish and mussel populations in the river system.