hi^h in the late afternoon when algal activity 

 was o-reatest. Concentration of dissolved oxygen 

 at the surface dropped to 5.6 p.p.ni. at station 

 PR5 in the early morning hours. 



Free carbon dioxide concentrations were 3.5 to 

 12.3 p.p.m. from to 15 m. in all samples at sta- 

 tion PE3, and no diurnal change was apparent. 

 Hydrogen-ion concentrations ranged from 7.4 to 

 8.3 in the surface waters at all stations. 



Additional limnological sampling was done 

 throughout March, April, and May 1963 at sites 

 of surface trap nets to measure limnological con- 

 ditions at each trap during the peak migrations 

 of salmon fingerlings. All sampling was during 

 daylight, normally between 0800 and 1600 hours. 

 Oxygen concentrations remained saturated or near 

 saturation (8-15 p.p.m.). Water temperatures 

 warmed gradually as the season progressed but 

 STATION I N. 



remained favorable for fish until the end of May, 

 wlien they rose to 23.9° C. All chemical determi- 

 nations were within acceptable limits for fish. 

 Samples taken at the trap sites did not differ ap- 

 preciably from those taken at established stations 

 in the same general areas of the reservoir. 



CURRENTS 



Continuous and instantaneous current measure- 

 ments are discussed in this section as well as wind 

 and other factors that affect surface currents. Sur- 

 face currents were considered of primary impor- 

 tance l)ecause most of the fingerling migrants re- 

 mained near the surface during the peak of the 

 downstream migration. Surface currents were, 

 therefore, recorded continuously to provide an ac- 

 curate description during any period. Instantane- 

 ous measurements were made during five periods 

 STATION II N. 



STATION III 



^^^-Veloclty m.p.s. 



Direction °/o of time 

 "^" Downstream direction 



RESERVOIR CONDITION 

 Period March 13 to April 17 



Pool status Filling 



Pool level -27.1 to -15.5 meters 



Inflow 511 c.m.s. 



Spill discharge 

 Total discharge 424 c.m.s. 



Figure f). — Direction (percentage of time, indicated by scale between center and upper margin of each figure) and 

 average velocity (m.p.s. .scale between center and lower margin) of currents recorded at 3-ui. depth in Brownlee 

 Reservoir during maximum drawdown. March 13 to April 17, 1964. Direction of current reads toward point of wedge. 



LIMNOLOGY OF BROWNLEE RESERVOIR 



317 



