1963 



1964 



JUNE 1-2 



Figure 2. — Continued 



PHYSICAL AND CHEMICAL PROPERTIES 



Temi^erature, oxygen concentration, current, 

 and other physical and chemical data are pre- 

 sented. Changes in these properties are described, 

 and comparisons are made between years. Diurnal 

 fluctuations of special interest are also described. 



TEMPERATURES 



The temperature regime of Brownlee Reservoir 

 differs somewhat from that in lai'ge, deep lakes, 

 but nevertheless shows the seasonal thermal 



changes of deeper lakes in the temperate zone: 

 spring turnover, formation of thermocline, and 

 fall turnover. In January 1963, the isotherms were 

 vertical from upper reservoir to the dam (fig. 2). 

 Temperatures in the upi:)er portion ranged from 

 0.5° to 1.6° C. ; those at the lower end ranged be- 

 tween 3.3° and 5.5° C. The isothenns remained 

 vertical until mid-March; then the isotherms be- 

 gan to align horizontally at depths below 49 m. 

 The January-March period is analogous in a 



LIMNOLOGY OF BROWNLEE RESERVOIR 



301 



