Chief Joseph 

 5 

 Wells 



Grand 

 Coulee 



3 2- 



WenatcheeiR. 



Rocky Reach 

 7 

 8^^%^ Rock Island 

 9 



Wanapum 



Priest Rapids 

 12 



.11 



Yakima R. 



19 



15 



16 



14 



Ice 

 Harbor 



RIVER 



22 2 



20 



18 



McNary 



17 



OREGON 



24 



23 



John Day 



The Dalles 



FiGiTRE 1. — Principal sampling stations on the Columbia and Snake Rivers. 



the turbines withdraw water from about 8 m. down 

 to 20 ni. at all the dams downstream from Chief 

 Joseph Dam. Maximum f orebay depths at full pool 

 do not exceed 45 m. Because of these facts and the 

 fact that temjDeratures in the forebay of the reser- 

 voirs seldom varied more than 1° C. from the sur- 

 face to tlie bottom, a sample at the surface and 

 10-m. depth was sufficient to represent the aver- 

 age forebay concentration and in turn represent 

 the water passing through the turbines and spill- 

 ways. Duplicate samples were collected at the sur- 

 face at stations below the dams where high current 

 velocities made it impossible to sample at depth. 

 Because the amount of soluble nitrogen depends on 

 water temperature/ the temj^erature of each sam- 

 ple was recorded before it was placed in an iced 

 cooler for transport to the laboratory. The use of 



' An iitmosphiric pressure o( 760 mm. mercury was used in 

 computing normal saturation (100 percent) for each sample. 



two aircraft made it jwssible to obtain all samples 

 in 1 day ; analysis was completed on the following 

 day. 



Water samples were obtained from additional 

 stations when more information was needed for a 

 specific dam or reservoir. For example, additional 

 stations were established along the reservoirs be- 

 hind McNary and Chief Joseph Dams to study 

 changes in nitrogen content of water passing 

 through these reservoirs. Additional stations were 

 also sampled when the effect of a specific dam on 

 saturation levels was examined. Table 1 gives a 

 detailed description of the principal sampling 

 stations and the dates when samples were obtained. 



ANALYSIS 



The amount of dissolved nitrogen in the sample 

 was determined by a modification of the technique 

 used by Swinnerton, Linnenbom, and Cheek 

 (1962). A Fisher blood gas analyzer Model 



U.S. FISH AND WILDLIFE SERVICE 



