bed is composed mainly of large rubble and boulders o Cascades 

 Occur through a large part of its course, and impossible falls 

 are located about a mile above the moutho l^ie stream maintains 

 a considerable flo^w throughout the year.. However, because of the 

 steep gradient, impassable falls, and lack of suitable spawning 

 area it was considered of little value to migratory fisho 



16Co Chewack Rivero-- (August II-I65 1935.S Whiteleather, 

 Shuman, and Biirrows o) The Chewack River enters the Methow at 

 Winthrop, approximately 48 river miles above the moutho The 

 streajTi is abouc 40 miles long, of #iich the lower 38 miles were 

 surveyedo The stream is passable to salmon in the lower 32 1/2 

 miles, up to Chevmok Falls o In the lower section the stream was 

 40=»70 feet wide, and at the upper terminus of the survey it was 

 about 20 feet widSo The discharge at the mouth was about 100 Cof cS^ 

 and in the middle sectionj, above all diversions, the flcm was about 

 20c OsfoSo The flow diminished rapidly in the upper section^ and 

 was reduced to 7 cofoSo at the upper end of the surveyo The water 

 temperature ranged from 53®F at the mouth to 43°'F in the upper 

 sectiorio The stream gradient in the lower 8 miles is 28 feet 

 per mileo It was estimated that the average gradient in the Icnner 

 30 miles was 42 feet per mile» and in the upper 7 1/2 miles surveyed 

 about 200 feet per milso There are numerous excellent salmon spawTi«= 

 ing areas well distributed throughout the courseo Resting pools are 

 few in the lower section, but are large and deepo Pools are smaller 

 and mors njaerous m the middle and upper sections o 



The Fulton irrigation diversion dam, located approximately 3/4 

 mile above the mouth, is about 3 feet high and has an apron extending 

 8 feet dowTistreamo It is a barrier to migratory fish at low vmter 

 stages o 



Tne Chewack irrigation diversion dam, located about 7 miles 

 above the mouthy is only 2 feet high, but is difficult for fish to 

 pass during the low water stages. 



At the time of the survey there were five irrigation diversions 

 on the streamo The total amount of water diverted was about 150 Oof o3o 

 None of these were screened at the time of the survey, but all of the 

 large permanent diversions later were screened by the Washington State 

 Deparlanent of FisherisSo 



The past history of this stream in regard to migratory fish is 

 the same as that of the rest of the Methow oystemo It was reported 

 that the Chewack was an excellent producing area for chinook salmon 

 in the early days and supported largs runs of tl-iat species o A run 

 cf steelhead trout persisted until the runs were intercepted at 

 Rock Islsuid on the main Columbia River in 1939o The former dams 

 and 'unscreened diversions on the main Methow River played a major 

 part in the depletion of these runso 



87 



