Sediment deposits in the Upper Illinois River are primarily of 

 urban origin (Butts, 1974), while agricultural sources probably make 

 the major sediment contribution in the middle and lower sections of the 

 river. 



Many farmers have removed vegetation from fence rows and stream 

 borders in order to obtain additional space for row crops. Erosion 

 from fields planted in row crops such as corn and soybeans is greater 

 than from field planted in crops such as wheat or hay. More powerful 

 tractors and wider tillage equipment make it possible for individual 

 farmers to farm increasingly large acreages, but it becomes increasingly 

 inconvenient to leave fence rows, grass waterways, marshy areas, or 

 meandering streams. The common practice of fall plowing leaves the 

 ground bare and subject to erosion during rains and snowmelt. Wind 

 erosion is probably also significant in moving soil into ditches where 

 it is later washed into streams and rivers. 



Sediment physically removes habitat by filling in areas; for 

 example, Lake Chautauqua, near Havana (river mile 124-130), lost 

 18.3 percent of its storage capacity in a period of 23.8 years (Stall 

 and Melsted, 1951). Areas in Quiver Lake, near Havana, where boats 

 could formerly be launched are now only a few inches deep during low- 

 water stages, and willows are encroaching on the lake. 



Sediments can also cause undesirable habitat modification by 

 blanketing firm bottoms, increasing turbidity, and reducing dissolved 

 oxygen levels. As pointed out earlier, many gamefish prefer to spawn 

 on firm, rather than flocculent bottoms. Many bottomland lakes and 

 backwater areas along the Illinois River have filled with a flocculent 

 sediment that has been described by Starrett (1959) : 



"The sediments in Lake Chautauqua are mostly 

 of a fine texture and form a loose, flocculent 

 'false bottom' (not similar to the type found in 

 bog lakes) over the original lake bottom. A slight 

 disturbance of the 'false bottom' causes particles 

 to become resuspended and so increases the turbidity 

 of the water ." 



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