oxygen has been small as compared to demands resulting from natural phenom- 

 ena, such as the decomposition of plankton organisms. Thus, from the chemica]. 

 point of view, the water of the Island Section seems to have been affected 

 very little by polluting materials known to enter the lake. 



Sewage Dilution in the Tributaries 



This investigation did not include a survey of the sources of pollution 

 on the shores of the streams enterin^; the lake, but it Is known that they are 

 numerous and of divers types. In the following pages, the chemistry of the 

 lake water near the mouths of four of the streams will be considered. Inter- 

 pretation of the results will be aided somewhat by a brief consideration of 

 the size of the streams and the concentration of population on their banks, 

 particularly near their mouths. 



Portage River is the smallest of the four streams. The discharge at the 

 mouth is not known, but certainly during the low water period in summer it is 

 small, for water frequently flows into the river from the lake. According to 

 observations made in the north branch of the river near Bowling Green, Ohio, 

 the dischc-rge is subject to wide fluctuations, with the highest water usually 

 in winter and spring, and the lowest in summer and autumn (U.S. Geological 

 Survey, 1927-1932) . There are no large centers of population on the river. 

 The principal source of sewage in the lower river is Port Clinton (population 

 li,U08) , which is situated at the mouth. Ninety per cent of the city's sewage 

 enters the river, and the remainder enters the lake nearby. In spite of the 

 lack of definite knowledge of the volume of discharge of the river, intense 

 pollution near the mouth is not to be expected, even at times of minimum dis- 

 charge, because of the added dilution which results from the frequent inflow 

 of lake water. However, current reversals in the river depend upon highly 

 variable physical factors, and it would be impossible to predict the fre- 

 quency of their recurrence, or their degree of influence on dilution in the 

 river. There is every reason to believe that, following discharge, dilution 

 should prevent any marked effect on the water of the lake. 



The discharge of Maumee River at, the mouth is not known, but at 

 Waterville, Ohio, about 2$ miles above the mouth, the combined discharge of 

 the river and canal for a period of nine years (1922-1930) was $,l4l7 cubic 

 feet per second (U.S. GeolO; ical Survey, 1925-1932). Presumably the dis- 

 charge at the mouth is onl'' slightly more than at Waterville, for no large 

 tributaries enter below that point. The flow is subject to large seasonal 

 fluctuations. For example, in 1930 it ranged from 63 second-feet on July 15 

 to 72,600 second-feet on January I6. The mean discharge Jn July, August, 

 and September for a nine year period was l,58Ii second-feet; it was somewhat 

 hither in the same months of 1929 (2,159 second-feet); but in 1930 it was 

 exceptionally low (201 seccnd-f eet) . Obviously the volume of water available 

 for dilution of sewage varies widely within the same year, and also for the 

 same period in different years. The river drains a populous district and 



86 



