Table 1. — Summary of minimum dissolved oxygen determinations near surface in channel of the Illinois and Des Plaines rivers 

 during summer months of 1911, 1912, 1922, 1923, 1925, 1926, 1928, 1950, 1964, and 1965. 



Nearest 

 Town 



Dissolved Oxygen in Parts per Million 



1911» 



1912" 



1922'' 



1923« 



1925'' 



1926'' 



1928'' 



1950" 



1964' 



1965' 



Lockport ... 0.01 



Channahon ... 0.2 



Morris 0.9 ... 0.2 



Marseilles 0.5 ... 0.1 



Ottawa ... 0.3 



La .Salle ... 0.5 0.0 0.0 



Peru 2.7 ... 1.7 



Spring Valley 2.0 ... 0.0 0.3 



Hennepin 2.2 1.8 ... 0.0 0.1 



Henry 2.1 1.0 0.4 0.0 



Lacon 2.1 ... 0.8 0.4 



Chillicothe 2.3 2.7 0.4 0.0 0.3 



Rome 1.9 ... 0.0 0,2 



Narrows (Peoria) 4.3 5.7 2.6 3.0 



Pekin 5.4 5.2 3.3 2.2 



Kingston Mines 4.1 6.6 3.0 5.5 



Havana 3.6 ... 1.3 3.8 



Browning 3.7 . ... 3.9 



Bcardstown 4.8 2 7* 2.3 2.7 



0.3 

 1.2 



0.5 



0.4 

 0.4 

 0,1 

 0.0 

 2.4 



0.6 



0.1 



0.2 



0.1 

 0.0 

 0.5 



2,4 



2.9 



5.3 



3.9 

 2.9 

 3.9 



4.9 

 3.5 

 2.9 

 5.1 

 4.8 

 5.0 



2.3 

 2.3 



1.6 

 4.1 

 2.5 

 2.8 

 5.1 

 4.9 

 5.1 

 3.8 

 3.0 

 2.7 



1.0" 



" Barlow (1913:40-45). 



'' Hoskim. Ruchhoft, & Williams (1927:114-122) Lowest of monthly mean determinations for Julv and .August 1922. 



■■ Greenfield (192.';:26-27 and 3(1-31). 



•> BorufT & Buswell ( 1929:57-1U8) . 



*■ Mondala. Chairman (Report of the Illinois River Pollution Commission. 195I:LA 41 Table I .-Xnalytiral Data of Illinois Sanitary Water Board). 



t Starrelt (Illinois Natural History Survey data). 



^' Mr. Ralph E\ans of the Illinois Water Survey furnished the data. 



* Samples laiten in 1921 rather than 1922. 



Studied the river in 1921 and 1922, said: "Growth of 

 the city of Chicago, with heavy increase in amount of 

 sewage and of stockyard waste overburdening the al- 

 ready polluted Illinois River, which, with reduced area 

 for overflow, limiting levees, and increased volume. 

 must therefore flow more rapidly in its narrowicl 

 channel, with the result that each succeeding year its 

 organic matter is carried fartiier downstream, before 

 the offensive organic content is sufficiently removed." 

 Richardson believed (1921b: 33) that in the 1915-1920 

 period the southward progression of this offensive condi- 

 tion in the Illinois Ri\i'r was iiitiviiig at the rate of 16 

 miles a year. 



Conditions upstream from Peoiia are niut li (lillnciit 

 now from those of about 40 years ago, as a coin|)arison 

 of the oxygen determinations made in 1922 and 196.") 

 indicates (Table 1). This improvenifut is interesting 

 when one considers the gieat growth that has been 

 occurring in population and industiy in the Chicago 

 metropolitan area. The improvement may ha\e been 

 due to several factors, including the construction and 

 operation of the tremendous sewage treatment plants 

 by the Chicago Sanitary District through a program 

 instittited in 1922. and the lock and dam sy.stem l)uill 

 in the I93f)'s whidi slowed up the moMiiifiU of the 

 water. The adoplicjn of belter water pollution laws by 

 the state also had its effect. 



Hoskins, Ruchlujft, & Williams (1927:2,5) stated 

 that the total combined domestic and industrial pollu- 

 tion cmiJtiicl into ihe Illinois Rivii in 1922 was the 



equivalent of that from 6,211,471 people. Tlie popula- 

 tion ec|uivalent of domestic and industrial wastes entering 

 the river in 1960 (United States Public Health Service 

 1963) had been reduced to 2,417.000, in spite of ex- 

 panding human populations and increased industry in 

 the basin. This change reflects the great progress which 

 has been made in the treatment of wastes and indicates 

 the magnitude of work yet to be done. 



In spite of the dramatic improvement described 

 above, our oxygen analyses made in 1964 and 1965 

 (Fig. 3) indicated that most of the river had less than 

 5 ppm dissolved oxygen. We consider the determinations 

 for the na\ igation pools to be (luite typical for nK)ining 

 samples during warm weathei. I he downward slopes 

 of the oxygon graphs below the clams (Fig. 3) are 

 similar for all pools but Starved Rock, which is affected 

 on the right bank by effluents from Marseilles and the 

 Fox River. The higher oxygen readings just below the 

 dams, and the declining curves as one proceeds down- 

 stream from each dam, indicate that additional oxygen 

 is added as the water |jasses over and tluough the dams 

 and locks, and that this is rapidly removed by the high 

 demand for the oxygen caused by the pollutants. Hartow^ 

 (1913:36) noted a similar increase in oxvgen in the 

 river below the Marseilles Dam in 1912. 



The similarity of the declines in oxygen below the 

 dams after the initial upsurge indicates that there arc 

 still high biological and chemical tiemands for the dis- 

 solved oxygen, and the amount available is at about a 

 breaking point insofar as fish life is concerned. 



