Ph2''sical limnology 



A general description of Lake Erie and a detij-iled description of West- 

 ern Lake Erie, vdth hydrographic maps and morphometric data, are presented. 

 The literature on fluctuations of lake levels, waves, seiches, tides and cur- 

 rents is reviewed briefly. Studies of curren-bs based on drift bottles show 

 that the surface currents of Western Lake Erie are not constant in direction, 

 but depend upon the direction of the vri.nd. 



Because of its extreme shallowness, Western Lalce Erie is usually homo- 

 thermous from top to bottom; thermal stratification appears only occasionally 

 and for short periods. Data on weather are presented. Transparency of the 

 water is low, particularly in spring and autumn. 



Chemistry 



In the Island Section the oxygen content of the surface water ranged 

 froTi 7.1 to 13."^ parts per million, and from B3 to 133 per cent of satura- 

 tion. Almost all of the samples fall between 90 and 99 per cent of satura- 

 tion. Free carbon d ioxide ranged from -5.9 to 3.1 parts per million; 

 methyl orange alkalinity (in terms of calcium carbonate) from 85 to 103 

 parts ner million; pH from 7.7 to 8.5. In general the chemistry of the sur- 

 face and bottom water was nearly the same. Only one case of nearly total 

 depletion of or-ygen in the lower water was found in the three seasons of 

 study. The low oxygen content (8.6 percent of saturation) was found in the 

 eastern part of the Island Section near the close of a period of temporary 

 thermal stratification, and apparently was restricted to the lower three 

 meters of water. 



The average amounts of the different forms of nitrogen in the Island 

 Section were as follows: free ammonia, 0.013; albuminoid ammonia, 0.151; 

 nitrite, 0.005, nitrate 0.10 (part per million). While it is probable that 

 the nitrogen content has been increased by pollution, it is equally probable 

 that the additional demand upon the dissolved oxygen has been small as com- 

 pared with demands resulting from natural phenomena. From a chemical point 

 of view, polluting materials known to enter the lake apparently* have had no 

 harmful effect on the water of the Island Section. 



The chloride content of Lake Erie is higher than that of other of the 

 Great Lakes. Chloride has little value as an index of pollution in Lake 

 Elrie because of the numerous natural sources of sodium chloride in the 

 drainage basin. 



A number of chemical samples were taken in Western Lake Erie near the 

 mojiths of four tributary streams (Portage, Maumee, Raisin, and Detroit 

 Rivers), and a few were taken in the rivers themselves. All of the rivers 

 are known to receive sewage from municipalities located on their shores. In 

 relation to its mean discharge, Maumee River receives sewage from the largest 



