5. WaUa Walla River .— (February 12-13, 193$ J and May 25, 1936 j 

 Suomela and Burrows.) Enters the Columbia River about 3 miles above 

 the Oregon-Washington boundary line and about 23 miles above McNary Dam 

 on the main Coltimbia River, The main stream is about 56 miles long 

 from its mouth to the confluence of its north and south forks, all of 

 •>*ich was surveyed. The average ifidth varied from 100-150 feet near 

 the mouth to 30-60 feet in the upper sections* The discharge into the 

 Columbia River at the time of survey was about 100 c«f»s« From the 

 mouth of the river to Mission Bridge (31 miles) the gradient is flat 

 and the stream is very sluggish* There are no suitable spamiing areas 

 in this section, and the flow during the summer irrigating season is 

 extremely low because of extensive diversions. However, the entire 

 section above Mission Bridge (25 miles) contains excellent suitable 

 spawning areas estimated to total 320,000 square yards, or in excess 

 of 80 percent of the stream bed. There is, however, a peculiar condition 

 present in the main river channel in this section that reduces tne value 

 of the spawning and rearing areas; for a distance of 2-1/2 miles below 

 the Freewater bridge the river is absolutely dry during the summer for 

 a period of from 2 to U months, effectively blocking the upstream and 

 downstream passage of fish. This is partly due to irrigation diversions 

 and partly to an absence of heavy sub-soil in the area. It is reported 

 that at no time since the late l880's has there been a flow of water 

 through this section during the summer* The extensive diversion of 

 water at the present time, of course, tends to cause this section to go 

 dry much earlier than in former years. It is said that this stream 

 section, known as the "Tumalum Branch", may go dry as early as May 15 

 in some years and in others as late as July 15« Because of the tremen- 

 dous seepage that occurs in this section it takes almost a month for a 

 normal flow of water to traverse it at the conclusion of the irrigation 

 season. 



There are fourteen dams and sixteen diversions on the main river. 

 Six of the dams and seven diversions are located below the "Tumaltim 

 Branch" and the others above. All of the dams are passable to salmon 

 and steelhead trout during high water stages, and only three are barriers 

 during low water. These are the Burlingame Dam and the two dams at the 

 Freewater bridge. They are not barriers because of size, but because 

 they cause the entire flow to be diverted during the irrigation season. 

 These three dams plus the Milton power dam, which is only 1 foot high, 

 are the only permanent structures. All of the others are visually car- 

 ried away by the spring freshets and must be rebtiilt each year. 



All of the diversions below the "Tumalum Branch" are screened, 

 but none of those above is provided with protective devices of any kind. 

 Since few, if any, adult salmon or steelhead are able to enter the 

 upper stream sections under present conditions there is no necessity for 

 screening these diversions from the standpoint of protection of anadrom- 

 ous fish. 



At the time of survey steelhead trout were being caught in the 

 main river above and below Mission bridge. However, the present runs 

 do not compare in size with those that entered the river in former years. 

 None of these fish were reported from the upper river sections. 



31 



