STREAM POLLUTION 
373 
the Mississippi River where good fish faunae were found and graph 6 D for all stations 
in the Mississippi River where medium, poor, or no fish faunae were found regardless 
of type of pollution. In this comparison the water at over 98 percent of the stations 
where good fish faunae were found carried 5 p. p. m. or more dissolved oxygen, and 
the water at 52 percent at stations where medium, poor, or no fish faunae were found 
carries less than 5 p. p. m. dissolved oxygen, but the water at 48 percent of the stations 
where medium, poor, or no fish faunae were found because of other unfavorable con- 
i. 
K. 
PERCENT tW' 0 
J. 
SO 
40 
30 
20 
10 
0 
MISSOURI HEADWATERS 
24 STATIONS 124 DETERMINATIONS 
2 4 0 6 10 12 14 
L. TENNESSEE 
116 STATIONS 326 DETERMINATIONS 
2 4 6 8 10 12 14 
DISSOLVED OXYGEN IN PARTS PER MILLION 
Figure 8.— Continuation of dissolved oxygen comparisons, stippled graph A in figure 6, being the standard. 
ditions, carried 5 p. p. m. or more dissolved oxygen due to current action and other 
factors in spite of the polluting materials. 
Three other observations may be made from these studies of warm-season dis- 
solved-oxygen values in the various streams and river lakes. Low dissolved oxygen 
was found more frequently in the impounded waters of streams, particularly if the 
impounded waters were subject to organic pollution, than in the more rapidly flowing 
portions of these same streams (see. graph 7 E of Hastings Pool, a notoriously polluted 
portion of the Mississippi River, and graphs 7 F and 111 ) ; head water streams, especially 
those in mountainous regions usually have high dissolved oxygen, and the range of 
