395 
Connecting lake-acreage per mile of river-length between Copperas 
Creek dam and Havana at the low gages of 1901 largely exceeded that 
in any other section of river above or below, the figure of 472.1 acres 
per mile being 57 per cent. more than between Chillicothe and the foot 
of Peoria Lake and 23 per cent. more than between Havana and the 
Lagrange dam—the two other reaches with the highest ratings. (Table, 
p. 378.) 
Though the eight or nine mile stretch of river just above Havana 
has had more shore vegetation at recent summer levels than any other 
section below Peoria Lake, the amount of vegetation bordering on chan- 
nel of normal width (excluding such areas as Havana Lake) has not 
in any recent season been very important. In a local flat stretch of a 
quarter mile on the west side above Liverpool, where there was more 
shore vegetation both in 1913 and 1914 than anywhere else between the 
dam and the head of Havana Lake, the extreme width of the weed strip 
was about 35 feet, a little less than 5% of the bank to bank width at 
the time (about 750 feet) ; while for most of the distance it was not more 
than 15 feet. Nowhere else between Copperas Creek dam and the head 
of Havana Lake was there in 1913 or 1914 shore vegetation for any im- 
portant distance that occupied more than a ten-foot strip next the bank, 
and there were long stretches with much less than that amount. In the 
shore zones of the wide water above the mouth of Spoon River there 
are several acres of Potamogeton on the west side in the most favorable 
seasons ; and on the east side a narrower strip, sometimes up to 50 or 60 
feet wide, in a stretch of about 300 yards along the edge of Cook’s 
Island. Even these local areas, relatively to the vastly greater river 
acreages wholly without aquatic vegetation in the 16.8 miles, are extremely 
small, and revert largely to open water in all but the driest seasons. 
Bottom Fauna.—A total of 16 channel collections and 23 collections 
in the shore zones (within the 7-foot line) were made in July—October, 
1915, between Copperas Creek dam and Havana in cross-section: at 
Bottom CoLLECTIONS, COPPERAS CREEK DAM TO HAVANA 
JULY—OCTOBER, 1915 
Ghanrel 4—7-ft.| 1—3-ft. 
zone zone 
1. Copperas Creek dam to Mile 129 
Mile 135.2, opposite head of Senate Island 4 2 
Mile 133.6, opposite foot of Senate Island 4 2 
2. Mile 129 to Havana 
Mile 128.5, 4% mile above Liverpool 5 5 4 
Mile 123.0, 3 miles above Havana 3 8 2 
Total ' 16 17 6 
