Aquatic Vegetation Mapping 
During both 1938 and 1939 maps have been made to scale 
Bhowing the aquatic plants found in the bottom-land lakes of the 
Tilinois Valley. These maps indicate the water depth and turbidity 
when the survey was made. A follow-up of the mapping is the col- 
dection during the hunting season of stomachs from ducks shot over 
the lakes previously mapped. The resulting information gives a pic- 
ture of what plants are chosen as food by ducks, and what the rela- 
tive abundance and distribution of these food plants is throughout 
the valley. Also learned is the area occupied by plants which do 
not produce duck foods. An accumulation of this information, aug- 
mented by special studies, should eventually yield a plan for re- 
ducing the area of non-food plants by increasing the area of food 
plants. 
A brief comparison between the conditions found in 1958 
and 1939 follows. 
In 1938 high water was prevalent throughout the valley 
mntil the latter part of July. A drouth then resulted in an abnor- 
mally low water stage throughout the remainder of the growing sea- 
mon for plants. The high water until midsummer precluded the 
growth of such important duck food plants as nut grass (Cyperus), 
duck millet (Echinochloa), saw grass (Leersia), a number of Smart- 
weeds (Polygonum) and pigweed (Acnida) from growing on the mud 
flats. Likewise, because of the fluctuating water levels and high 
turbidity, few important aquatic plants upon which ducks feed were 
able to thrive in the parts of the lakes which did not go dry. The 
two most abundant plants in the bottom-land lakes of Illinois, 
American lotus (Nelumbo lutea) and the river bulrush (Scirpus flu- 
viatilis) are rclatively unimportant as duck food producers. ~ _ 
Thus, during the hunting season of 1938, there was a 
Pscarcity of natural duck foods in most of the lakes, and the water 
Jevel was so low as to make many lakes veritable mud flats. Such 
Cnvironmental conditions led the ducks to concentrate in areas 
possessing a bountiful supply of natural food, and to rest in the 
@cnter of large lakes during the day, procuring their food from 
Cornficlds during the evening and morning hours. 
A new factor entered the picture in 1959. Two wicket 
type dams--one at Whitechousc, near Pekin, the other at La Grange, 
below Ecardstown--were placed in operation to compensate for the 
low water stage brought about by reducing the diversion from Lake 
Michigan. The Whitchouse dam raiscd the water in the Illinois 
River and adjoining lakcs from Pekin to Hennepin; the La Grange dam 
raised the water level as far as Browning and the Sangamon River. 
Between Pekin and browning the lowest stage in the recent history 
Bt the Illinois River prevailed during August and September of 1959. 
BPormcr large lakes, such as Clear, Quiver and Crane, became. little 
more than puddilcs. 
