COMMERCIAL FISHERIES REVIEW 



Vol. 28, No. 9 



and obtain samples to determine turbidity, dissolved oxygen, and pH (fig. 10). The dissolved oxy- 

 gen measurements were taken at three points: (1) 25 feet upstream from the air curtain, (2) 25 



feet downstream, and (3)75 feet downstream. 

 Two samples for oxygen and pH were taken at 

 each of those points, one at the 6 -foot depth and 

 the other at the 15 -foot depth. In addition, a tur- 

 bidity sample was taken 2 5 feet upstream from 

 the air curtain. Other samples also were taken 

 at various other locations in the river system 

 throughout the study period but these are not 

 shown in this report. These included the Me- 

 nomonee River, Kinnickinnic River, and at va- 

 rious points inthe Milwaukee River northward 

 to the North Avenue dam. All samples were 

 taken by lowering a dissolved oxygen sampler 

 from the boat to the depths indicated. Dissolved 

 oxygen was determined by the improved Wink- 

 ler method. The samples were first stabilized 

 on the boat and thentransferred to the labora- 

 tories for final determination. Turbidity and 

 pH were also measured inthe laboratory. Tur- 

 bidities were determined with a fluorometer. 

 The temperature was taken by the personnel in 

 the boat with a thermister lowered into the wa- 

 ter to the various depths. Allresults were re- 

 corded for later analysis. 



RESULTS OF CHEMICAL AND 

 PHYSICAL TESTS 



The levels of dissolved oxygen were 

 lower downstream from the air curtain than 

 they were upstream. The Menomonee River was extremely low in dissolved oxygen concen- 

 trations. The mixing of waters of the Menomonee River and Milwaukee River resulted in low- 

 er dissolved oxygen readings, both 25 feet and 75 feet below the air curtain. 



The dissolved oxygen determinations (table 1) revealed that the median dissolved oxygen 

 75 feet upstream of the air curtain was 1.25 mg. per liter at the 6 -foot level and 1.50 mg. per 

 liter at the 15 -foot level. The median at the sampling point 25 feet downstream was 1.35 mg. 

 per liter at 6 feet and 1.45 mg. per liter at 15 feet. At the point 75 feet downstream, the 6- 

 foot depth showed a median dissolved oxygen content of 1.40 mg. per liter, while at 15 feet 

 the reading was 1.20 mg. per liter. These changes apparently result from the influence of 

 the Menomonee River and stratification as the two rivers combine. As stated previously, the 

 dissolved oxygen during the study steadily decreased during dry weather until the influence 

 of the fresh water from the flushing tunnel was noted at the sampling points. 



Samples taken upstream in the Milwaukee River showed increasingly more dissolved 

 oxygen to the North Avenue dam, while the Menomonee River was low in dissolved oxygen, 

 which may account for the heavier fish kill observed there. The dissolved oxygen in the Mil- 

 waukee River was less than 0.5 p. p.m. when the flushing was resumed. The low oxygen con- 

 tent indicated that the river was in a critical state and that flushing was necessary. The aver- 

 age daily water temperatures varied from 61.5° F, through 73° F. during this period. The 

 mean turbidity in the Milwaukee River was 37 p. p.m. during the study period (see table 1), 

 the median pH was 7.63. 



OBSERVATIONS 



The migration of alewives into the Milwaukee River during the test period appeared er- 

 ratic. During previous years, fish entered the river to spawn from mid-May through mid- 



Dissolved oxygen detemiinaiiun. 



