During the summer and fall, mud flats are often present on back- 

 water lakes and sloughs of the Illinois and Mississippi Rivers. Be- 

 fore the nine-foot channel project, only limited acreage of mud flats 

 occurred. Although these mud flats were inundated by the rising water 

 levels created by implementation of the navigation channel, shallow 

 areas surrounding bottomland lakes and sloughs have increasingly filled 

 with silt. This process has destroyed productive marsh areas, but has 

 recreated mud flats available for moist soil food production. The acres 

 of mud flats now exceed the number present before the nine-foot project. 



The nine-foot channel project initially created more water areas 

 and stabilized low-water fluctuations which were beneficial to aquatic 

 plant communities and subsequently fish and wildlife. Tables 35 and 36 

 list the acres and species of plants recorded by Dr. Frank Bellrose 

 from 1941 to 1944 for Flat and Gilbert Lakes (Pool 26) which are loca- 

 ted at the confluence of the Illinois and Mississippi Rivers. This 

 area is indicative of the productive areas created by the expansion 

 and stabilization of water levels in Pool 26. As a result of increased 

 turbidity and sedimentation, the biological productivity of these areas 

 has been reduced since the creation of Pool 26. Sedimentation was first 

 mentioned as being a problem by a refuge manager as early as 1947, when 

 it was suggested that Swan Lake (Pool 26) be protected by dikes. By 

 the late 1960 's submerged aquatic plant production began to decline. 

 After major floods in 1969 and 1970 these plants have nearly disappeared 

 from the Calhoun and Batchtown units of the Mark Twain National Wildlife 

 Refuge (narrative reports) in Pools 26 and 25. As a result of increasing 

 sedimentation and turbidity, many productive areas which initially 

 supported luxurious aquatic plant growth and provided habitat for fish 

 and wildlife have been degraded. 



128 



