404 



VARIATIONS IN LAKE LEVELS 

 Lake Superior 



Indies 



Jan 



Feb 



Mch 



April 



May 



June 



July 



Aug 



Sept 



Oct 



Nov 



Dec 



Jan 



Feet 



3 

 2 

 7 

 o 



4 

 3 

 2 

 7 

 O 



4 

 3 

 2 

 / 

 O 





























7 

 2 

 3 



4 

 O 



1 



2 

 3 

 -4 



7 



2 

 3 

 4 



















/~^. 



























r x 











































" 







■/ 

























































""-i 





























"S. 



























> 













s 

















\ 



































-^ 























N^ 

























*■•- 

























































































































































Lake Michigan 































































* J 































N 























'"" 







. 



'^"^"^^ 

















* 













- 





















































































■*^, 























— 



-— 

























































































.^■— -— 



























































































































Lake Huron 



























































































































s 



















j 







** 











'V 









. 



• 





























































































































































































- 



























































— --. 































■"^ '• 































































MEAN MONTHLY VARIATION IN LAKE LEVELS AND PRECIPITATION 



time of maximum stage providing the amount and intensity of 

 precipitation are known. As the drainage basin increases, how- 

 ever, the problem becomes one of greater complexity and the 

 correspondence between precipitation and water stages is not so 

 definitely marked. 



The important oscillations in the surface level of the Great 

 Lakes may be conveniently divided into two classes, viz., annual 

 or periodic, and irregular or non-periodic. The first of these con- 

 sist of a rise from low water of winter to high water of midsum- 

 mer, followed by a return to low water, the entire range from 

 low to high water rarely exceeding a foot. The irregular or non- 

 periodic variations also consist of oscillations up and down about 

 a general mean level ; but, unlike those first named, they may 

 range through several feet and persist in a single direction for a 

 number of years. Lakes Michigan and Huron, it may be re- 



