Mississippi River, Missouri & Illinois

Creating optimal conditions for aquatic vegetation through flexibility in dam operations

The Upper Mississippi River in Illinois and Missouri supports a major navigation route as well as many other needs. In the late 1980s and early 1990s, aquatic vegetation nearly collapsed. Unique hydrologic conditions required low end river operations in 2014 and an additional benefit was the reappearance of perennial aquatic plants.

A collaborative effort is allowing for lower water levels when conditions permit to determine longer term effects on these plants and river operations.

Mississippi River

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Aquatic vegetation in the Upper Mississippi River nearly collapsed in the late 1980 through early 1990. Looking for solutions, river managers began to evaluate with the US Army Corps of Engineers whether regaining some seasonal variability in water levels could regenerate the aquatic plant community. Historically water levels would rise in spring with snow melt and spring rains and fall off during the summer growing season and these seasonal changes create optimal conditions for plant germination and growth. Lock and dam operation maintains water levels higher in the summer months for commercial navigation, degrading conditions necessary to maintain plant communities.

The U.S. Army Corps of Engineers, St. Louis District and natural resource agency partners determined there was some flexibility in dam operations and depending on annual river hydrology the dams could be operated at the lower end of operational band. Initial demonstrations targeted a 30‐45 day window during the growing season to regain the annual aquatic plant community, essential for migrating waterbirds in the spring and fall. The demonstrations started in 1994 and continued through 2014 at Locks and Dams 24‐26.

A unique hydrological event in 2014 required the U.S. Army Corps of Engineers to maintain operation at the low end of operation for over 85 days. Not only did annual aquatic plant respond to the extended low water conditions but perennial aquatic plants reappeared, which had not been observed for over 20 years. With these observations, USACE and river partners decided to adapt this practice to hold water levels lower for an extended portion of the growing season (goal of 90+ days) if hydrologic conditions allowed. This change was implemented in 2015 and will continue through at least 2018. Response from these operational changes will be assessed to determine future implementation goals.



  • Operation and Maintenance
  • Water Control Management
  • Sustainable Rivers Program - beginning with 2015 adaptive management
  • Illinois and Missouri State agency monitoring
  • Long Term Resource Monitoring (Upper Mississippi River Restoration)


  • River Resources Action Team 
  • U.S. Army Corps of Engineers, St. Louis District
  • MVS
  • MDC
  • Missouri Department of Natural Resources
  • Illinois Department of Natural Resources
  • US Fish and Wildlife Service - Endangered Species and Refuges
  • The Nature Conservancy 
  • Various other NGOs and private groups


  • Garvey, James E.; Dugger, Bruce D.; Whiles, Matt R.; Adams, S. Reid; Flinn, Michael B.; Burr, Brooks M.; and Sheehan, Robert J., "Responses of Fishes, Waterbirds, Invertebrates, Vegetation, and Water Quality to Environmental Pool Management: Mississippi River Pool 25" (2003). Reports. Paper 4.
  • Benjamin, G. L.; Rogers, A. J.; and K. J. Killgore. Mississippi River Ecosystem Restoration: The Past Forty‐ Plus Years. American Fisheries Society Symposium 84:000–000, 2016. Chapter 15.
  • Kenow, K. P., G. L. Benjamin, T. W. Schlagenhaft, R. A. Nissen, M. Stefanski, G. J. Wege, S. A. Jutila and T.J. Newton. 2015. Process, policy, and implementation of pool‐wide drawdowns on the upper Mississippi River: a promising approach for ecological restoration of large impounded rivers. River Research and Applications. DOI: 10.1002/rra.2857.

Web links to related efforts

  • http://mvs‐wc.mvs.usace.army.mil/epm/epmindex.html 
  • http://opensiuc.lib.siu.edu/fiaq_reports/4 


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