10 20 30 10 20 30 10 20 30 10 20 30 10 20 30 10 20 30 10 20 30 10 

 JAN FEB MAR APR MAY JUN JUL 



20 30 

 AUG 



FIG. 6 Ten-day average N 2 gas level at Prescott, Oregon, 

 January through August, 1972, 1973 and 1974. 



GAS EQUILIBRATION CHARACTERISTICS 

 IN THE COLUMBIA RIVER BETWEEN THE 

 DALLES DAM AND ASTORIA, OREGON 



Two surveys were done during 1974 to deter- 

 mine the mixing characteristics and rate of gas 

 equilibration in the Columbia River between The 

 Dalles Dam and Astoria, Oregon. One survey was 

 done between Bonneville Dam and Prescott on 

 April 9 and 10 and another between The Dalles 

 Dam and Astoria during June 11 to 14, 1974. 



Methods 



An 18-ft survey boat floated with the water 

 mass following a 2.4-m long buoy which iwassub- 

 merged except for the top 0.6 m; the buoy was 

 equipped with a light for night drifting. Transec- 

 tional and/or single water samples were taken 

 at least every 10-12 river miles (Fig. 7) and 

 returned to Prescott for analysis. Time delay on the 

 samples, between collection and analysis, was 

 never more than 12 hr. 



Mixing and Equilibration Between 

 Bonneville and Prescott — April 1974 



Table 4 is a summary of the results of 

 the survey. The "float" time between Bonneville 

 and Prescott was approximately 26 hr. The average 

 total outflow from Bonneville Dam was 8.1 KCMS 

 (286 KCFS) during this period. Bonneville fore- 

 bay and power house samples each showed 115% 

 N 2 saturation at the beginning of the survey. 

 The N 2 saturation in the spillrace (3 transect sam- 

 ples) ranged from 123 to 130%. Table 4 shows side- 

 to-side mixing (within error of analysis) at Rooster 

 Rock (RM 130), approximately 15 miles down river 

 from Bonneville Dam. Below Vancouver the N 2 

 values were apparently influenced (decreased) 

 by the inflow from the Willamette River. The N 2 

 level decreased approximately 10% between Bonne- 

 ville and Prescott. 



WASHINGTON 



THE DALLES 



FIG. 7 Sampling locations used during a study to determine gas equilibration characteristics in the Columbia River between The Dalles 

 Dam and Astoria, Oregon. 



76 Blahm, McConnell, Snyder 



