Tfratero About 1 mile upstream from the falls there is a log jam 20 

 feet high, which is completely filled in with sand and rooks so as 

 form a total barrier to fish* There is one irrigation diversion 

 located about i/2 mile above the moutho At the time of observation 

 this ditch was withdrawing about 9 cf.So, and was not screened* 

 However, it is reported that it is now screened^, The stream was 

 32 feet wide at the mouth and was discharging more than 40 Cef«s» 

 at the time of observationo At the upper ond of the survey the 

 stream was only 12 feet wide and was flowing about 12 CefeSc The 

 water temperature ranged from 53°F« near the mouth to 47 F© in the 

 upper sectiono Th^ stream gradient is steep, being 150=250 feet 

 per mile, and cascades are numerous-. Good spawning area is very 

 limitedo It was reported by loc&l residents that the West Fork 

 had never supported significant runs of salmon or steelheads. The 

 stream appeared to be of little potential value for the production 

 of salmon. It is possibly of some value to steelhead trout. 



18o Okanogan River e°° (December, 1934, Suoraela and Christyjs 

 August; 1936, Hanavan and Whiteleather^) Enters the Columbia River 

 near Brewster, Washingtono The river extends for 80 miles to Lake 

 OoOyoos, on the International Boiindary, continuing upstream into 

 Canada about 40 miles farther to its source in Lake Okanogan* 



The river system within the United States was entirely surveyed, 

 and permission was obtained for several fishery reconnaissance 

 expeditions into Canada » 



The discharge from the Okanogan varies considerably throughout 

 the water-year. Records of the Ua, S» Geological Survey for the 

 water-year 1943-44 taken at a point 5 i/2 miles south of Tonasket, 

 Washington, or approximately 50 miles above the mouth, give a 

 HiELxirn'om discharge of 10,000 cof.Se in Jtme, esid a minimum discharge 

 of 225 c.foSo in January* 



The s\jmraer temperatures of the Okanogan River are extremely 

 high, often reaching the high seventies below Lake Osoyooso 



The stream gradient is generally slight throughout the entire 

 course. A considerable amount of water is taken from the river 

 between the mouth and Lake Osoyoos, but it is all withdrawn by 

 means of pumps. The intaks of these pumps are all screened to 

 keep out trash, and none of them are large* Therefore, it is 

 believed that they do no damagd'to fishc 



The Zosel mill dam, located at Oroville, is about 4 feet high* 

 It recently has been provided with an improved f ishway. 



The diversion dam about 8 miles above Oliver, British Columbiap 

 and below Lake Vaseaux is the present upper terminus of fish migrations* 

 This dam is about 6 feet high, and is a total .barrier to fish. It 

 was reported that the dam once was provided with a fishway, which was 



92 



