Sedimentation 



In order to determine the rate of sedimentation and fill of Lake 

 Meredosia located on Pool 26 of the Illinois River (river miles 72-78) , 

 six depth transects were taken. Depths were taken through the ice at 

 approximately 200-foot intervals with an aluminum pole fitted with a 4.5- 

 inch diameter aluminum foot. The depths were correlated with the Illi- 

 nois River gauge at Meredosia to determine mean sea level elevations. 



The sedimentation and fill rates were calculated by comparing our 

 depths with those recorded in 1903 by W.J. Woerman, U.S. Army Corps of 

 Engineers, and depths recorded by the Illinois Division of Waterways in 

 1956. The water depths from the Woerman maps were converted from Memphis 

 Datum to MSL (1929 general adjustment) by subtracting the conversion 

 factor of 7.345. 



Terrestrial Communities 



Wetland Plants 



Aquatic and moist soil plant acreages were obtained by planimetering 

 vegetation maps. These maps had been drawn using inspection and rough 

 triangulation by Frank Bellrose from 1941 through 1944. Species were 

 listed according to taxonomic order from Gray's New Manual of Botany 

 (1908). Changes in vegetation from 1946-1976 were procured from annual 

 narrative reports of the area managers for the Mark Twain National 

 Wildlife Refuge. A recent study of vegetation (Klein et al., 1975) in the study 

 area was reviewed. 

 Population Data 



The population data for waterfowl, cormorants, and bald eagles were 

 obtained from the 1956-1977 fall waterfowl censuses made by the Illinois 

 Natural History Survey. Waterfowl use was expressed as duck days. This 

 was calculated by totaling the weekly censuses from October 1 through 

 December 1 and multiplying by seven. Each duck-day represents one duck 

 spending one day in the study area. Bird population data for the 



