T-\BLE 4. — Prevailing u'ind direction at station 14 during 5 

 reservoir stages {determined from single daily observations), 

 March to August 1964 



Reservoir stage 



Wincl direction 

 North South Cahn 



Maximum drawdown Mar. 6-Apr. 17.. 



Sustained pool minus, 13.1 m. Apr. 18-May 22.. 



Fill-up— no spill May 30-June 5.. 



Full pool— spill June 13- June 26. 



Full pool— no spili July 2-Aug. 25.. 



Percent 



36 25 39 

 57 17 26 

 57 43 

 50 22 28 

 73 2 25 



Factors That Influence Surface Currents 



Surface currents are highly important because 

 most of the juvenile salmonids were near the sur- 

 face upon entry into the reservoir and for some 

 time thereafter. The primary factors that aft'ected 

 surface currents at the three stations were as 

 follows : 



Station I ( lower reservoir) — rate of discharge 



and wind 

 Station II (middle reservoir) — resen'oir 



drawdown, rate of discharge, and wind 

 Station III (upper reservoir) — resen^oir 

 drawdown and rate of river inflow 

 Surface currents at station I were not well 

 oriented downstream except when the rate of dis- 

 charge was increased at the spill (figs. 10, 11, and 

 13). Wind was the main factor atfecting currents 

 when there was no spill. 



Cui'rents at station II were well oriented down- 

 stream during two periods — maximmn drawdown 

 at minus 27.1 m. and at the minus 13.4-m. level 

 with apill (figs. 9 and 10). During the rest of the 

 study period, currents at station II were oriented 

 upstream about as often as downstream. The wind 

 again seemed to exert a disorienting influence. 



Currents at station III were well oriented down- 

 stream except at full pool and at full pool with 



spill. Although wind seemed to be the most impor- 

 tant disorienting factor at full pool, it had less 

 etfect on the surface currents at the upper end of 

 the reservoir than at the middle and lower areas. 

 "Water velocities at station III were usually in ex- 

 cess of 0.1 ") ni.p.s. ; consequently, considerable wind 

 was needed to alter significantly the general down- 

 stream current pattern. A wind of high velocity 

 bldwing in a rever,se direction for a short- time 

 might deflect the surface current somewhat, but 

 it would not reverse it. 



The instability of currents in the upper end of 

 the reservoir during full pool with spill and high 

 river inflow ( fig. 13) was pi-obably due to the spill 

 rather than to the wind. Possibly a seiche efi'ect 

 was created during the heavy spill, which caused 

 stronir vertical currents near the convergence line. 

 Repeated observations of the movement of the 

 convergence line indicated a definite shift down- 

 stream during spilling. When the convergence line 

 moved downstream to the vicinity of the current 

 monitor at station III, the downstream orienta- 

 tion of the current suffered a definite breakdown. 



EFFECTS OF BROWNLEE RESERVOIR ON 

 WATER QUALITY OF SNAKE RIVER 



Temperature, dissolved oxygen, and total alka- 

 linity were measured in 1963 at three stations 

 along the Snake River: (1) above Brownlee Res- 

 ervoir (Weiser, Idaho), (2) below Bi'ownlee Dam 

 (interstate bridge), and (3) below Oxbow Dam 

 (powerhouse tailrace). The data are plotted in 

 figure 20 to show the eifect of the Brownlee- 

 Oxbow complex on the inflowing river waters 

 from April through December. Upstream from 



Table .5. — Wind velocities and direction recorded during instantaneous current measurements in Brownlee Reservoir, March 



to August 1964 



330 



U.S. FISH AND WILDLIFE SERVICE 



