obtained had the sky been clear. Certainly the data show no evidence 

 of pollution. However, it should not be assumed that all parts of 

 the river would show the same satisfactory results. Sewage enters 

 the river near the shore and there is a decided tendency for it to cling 

 to the shore as it moves down stream. At the level of Ambassador Bridge 

 and Fighting Island there would be little mixing of sewage and river 

 water, so that the observed results in raid-stream are not surprising, 

 but one would expect to find definite evidence of pollution along shore. 



Below Fighting Island little sewage enters the river, and there 

 is abundant opportunity for dilution of the sewage received farther up 

 river. For that reason it seems probable that the results obtained at 

 Station 126 (Table U2) are fairly representative of Detroit River water 

 at the mouth. Conditions at Station 219, near the Canadian shore, were 

 similar to those at Station 126 on the same dates of 1930. As stated 

 before, the United States side of the river receives more sewage than 

 the Canadian side, and also has a more sluggish current in the lower 

 part of the river. But if these circumstances give rise to unfavorable 

 chemical conditions in any considerable part of the water below Grosse 

 Isle, one would expect to find evidence of it at Station 126, because of 

 its position, which is nearer the west shore than to the east shore. 

 Failure to find such evidence is doubtless due, principally, to great 

 dilution of the sewage. Contact with the air would aid in r ecovering 

 any oxygen lost, but photosynthesis must play a relatively minor part 

 because of the scarcity of phytoplankton in the river. 



The literature on pollution of streams contains many examples 

 of complete or almost complete exhaustion of oxygen. Wiebe (1928) in his 

 study of the upper Mississippi, reported several stations within and 

 below Minneapolis and St. Paul which had little or, no oxygen in August, 

 1926, The explanation of the difference in the amount of oxygen there 

 and in lower Detroit River is to be foimd in the relative capacity for 

 dilution. In August, 1926, the discharge of Mississippi River at 

 St. Paul was 2,810 cubic feed per second, and the discharge of Detroit 

 River in August, 1930, was roughly 202,000 cubic feet per second. The 

 combined population of Minneapolis, St. Paul, and South St. Paul in 1930 

 was 7h5,971, and the combined population of cities contributing sewage 

 directly to Detroit River in 1930 was l,850,3UO. Assuming that the 

 per capita output of sewage was the same in the two regions, dilution in 

 Detroit River would have been roughly 29 times as great as in Mississippi 

 River, The importance of dilution is shown by the fact that in 

 September, when the discharge of the river had increased to 8,630 cubic 

 feet per second, Wiebe found that the amount of oxygen at the badly 

 polluted stations increased tremendously. For example, at a point just 

 below the Twin Cities, there was no oxygen on five consecutive days in 

 ndd-August, On the same days of September, there was an average of 



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