312 



lii.iNois Natlrai. History Survey Bulletin 



Vol. 28, Art. 2 



the Sanjiamon, Salt Fork. Middle Fork, 

 and to a lesser degree the Embarrass rivers 

 ha\e narrow floodplains. which may be 

 completely inundated during floods. Se- 

 vere dry periods occur nearly every year, 

 usually during August and September. 

 The flow may decrease drastically or even 

 cease. The small headwater tributaries 

 suffer most regularly and severely from 

 dry weather conditions. 



Water temperatures in small, shallow, 

 stagnant pools may approach 100 degrees 

 F. during the summer and 32 degrees in 

 the winter. There are no large springs to 

 moderate water temperatures. The lack 

 of shading bank vegetation along shallow 

 areas allows extreme daily fluctuations of 

 temperature, which, in summer, may 

 change as much as 20 degrees F. between 

 the cool morning hours and the hot mid- 

 afternoon. In winter, temperatures may 

 drop sufficiently to freeze the water to 

 the stream bottom in shallow areas. Be- 

 cause fish generally concentrate in deep 

 pools, the\' are seldom caught in the ice. 



The distribution of bottom materials, 

 formed from the basic glacial till, is di- 



rectly related to the velocity of the water. 

 Through selective sorting of the basic ma- 

 terials, rubble and gravel (the heaviest 

 materials) pile up in riffle areas, sand in 

 areas of moderate current, and the finer 

 particles of silt and clay drop out only in 

 the quiet waters of the deep pools. 



Turbidity is generally high, becoming 

 low only during the cold months, when 

 the activity of fish is reduced so much 

 that it does not roil silt on the bottom 

 and when streams are said to be "winter 

 clear." During the field work for the 

 present study, turbidity ranged between 

 15 and 150 parts per million (p. p.m.). 



The chemistry of stream water, bas- 

 ically related to the mineral composition 

 of the watershed, may be strongly in- 

 fluenced by domestic and industrial pol- 

 lution, table 3. Water in the lower Em- 

 barrass, Kaskaskia, Spoon, and Sangamon 

 rivers, which are relatively unpolluted, is 

 low in ammonium, phosphate, and nitrate, 

 in comparison with w'ater from the pol- 

 luted areas in the Salt Fork River. Hard- 

 ness (as calcium carbonate content) ranges 

 from 264 to 436 p. p.m. The pH is slightly 



Table 3. — Partial chemical analysis of water collected from seven stream locations in 

 Champaign County on December 29. 1960. The streams were mostly ice covered and at normal 

 water level. Temperatures of samples ranged from 32 to 34 degrees F. The water had no 

 measurable color or odor. Turbidity was less than 24 p.p.m. Analysis was made by the Illinois 

 Water Survey. All figures are for p.p.m. 



Station 



Embarrass 



North of Villa 



Grove 



Sangamon 



Northeast of 



Mahomet 



Kaskaskia 



West of 



Parkville 



Spoon River 



North of 



St. Joseph - 

 East Branch 



North of 



St. Joseph 

 West Branch 



East of 



Frbana 

 Salt Fork 



Northwest of 



Homer 



2 

 O 



< 



0.2 



0.3 



tr. 



0.5 



7.4 



7.5 



4.8 



a 

 H 

 < 



2.8 



5.8 



6.5 



2.4 



18.2 



14.9 



15.9 



to 



304 



303 



320 



292 



360 



312 



03 ^^ 



284 392 



428 



264 



436 



372 



376 



336 



Q CO 



> < 



-: J « 



<■ O t] 



2; f z 



c f" 2 



477 



555 



370 



850 



842 



705 



, ^ z 



-J u £ 



^ z ^ 



*C 35 <xi 



0.0 



0.1 



0.1 



555 0.0 



0.7 



1.2 



0.9 



