at times of major clianges in reservoir conditions. 

 These periods are the same as those described 

 under continuous recordine except for the period 

 described as till-up at minus 20A m. from full 

 pool level. The instantaneous measurements pro- 

 vide infcn-mation on subsurface currents. 



Continuous Current Measurements 



The averarres (percentages of time) are given 

 for surface current direction and velocity readings 

 (m.p.s.) recorded by continuous current recorders 

 at three midchannel stations (station I — lower res- 

 ervoir; station II — midreservoir ; station III — 

 upper reservoir) during each of five periods. These 

 periods covered the major changes in inflow and 

 outflow and fluctuations of reservoir level from 



maximum drawdown in March 1964 through fill- 

 up in August 1964 — the time of the major finger- 

 ling migration through the reservoir. All current 

 meters were maintained at a depth of 3 m. 



The terms "downstream," "upstream" (reverse), 

 and "cross reservoir" are used throughout this sec- 

 tion of the report to describe, direction of currents. 

 Upstream and downstream currents did not devi- 

 ate more than 60° from the downstream axis ; the 

 others were cross currents. 



Conditions in the reservoir include maximmn 

 drawdown, sustained minus 1.3.4-m. level with 

 spill, fill-up with no spill, full pool with high spill, 

 and full pool without spill. 



Maximum drawdovm. — Maximum drawdown 

 (minus 27.1 m.) was on March 18, 1964. The mean 



STATION I 



STATION III 



STATION II 



52% 



^^^^ Velocity m.p.s. 



Direction % of time 

 ^^ Downstream direction 



RESERVOIR CONDITION 



Period April 18 to May 22, 1964 



Pool status Sustained -13.4m. level 



Pool level -13.4m. 



Inflow 731 cms. 



Spill discharge 430 c.m.s. 



Total discharge 740 c.m.s. 



Figure 10. — Direction (iiercentage of time, indicated by .scale between center and npper margin of eacli figure! ana 

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

 Reservoir during sustained 13.4-m. level with spill, April 18 to May 22, 1!>C4. Direction of current reads toward 

 point of wedge. 



318 



U.S. FISH AND WILDLIFE SERVICE 



