34 



J. E. Hobbie 



Pre-Melting Post-Melting 



29 May to 3Jun 14 to 17 Jun 



Snow Melting 

 4 to 13 Jun 



Freeze -Up 

 25 Aug to I Sep 



Mid-Summer Mid-Winter 



15 to 28 Jul StolOFeb 



80- 



o 



J3 



eO 



o 



(D o>4 



o in 

 o <o 



^1 

 CO ^ 



=■0 



o 

 a: 



4r- 



c 

 o- 



o ^ 

 "^ F 



Measured 



Computed 



0.1 



0.2 



0' 



_ 4J__ 

 '4;2(est.)' 



3.0 



2.6 



0.7 



^ 



-0.05 



FIGURE 2-4. The evaporation rate and factors that affect it for 

 six characteristic periods. Evaporation rates reported are from 

 pans. (After Welter and Holmgren 1974.) 



sediments and melts a little ice there. In general, it takes only 4 days for 

 the pond ice to melt completely. 



In lakes, the same events take place but the 2-m-thick ice sheets take 

 much longer to melt. Consequently, the ice does not melt completely in the 

 deeper.coastal lakes until early- or mid-July, depending upon the thickness 

 of the ice at the beginning of melt. Other complicating factors affecting the 



