Above this canyon the river opens into another flat valley, 

 which extends 12 miles upstreamo The flow was about 50 c.f.So in the 

 lower part of this section, and the water temperature was 780O F, 

 The gradient is very slight The stream bed is composed chiefly of 

 mud amd silt, and is of no value as spawning area for salmon. An 

 irrigation diversion dam about 2 feet high and 66 feet long is loca- 

 ted about 1,3 miles above Keating, or approximately 37^ miles above 

 the mouth. This dam is not a serious obstacle to fish. The ditch 

 withdraws about h c.f.So 



Above the Lower Powder Valley the river extends for 18 miles 

 through the narrow, steep. Thief Valley Canyon, This is an arid, \m- 

 inhabited regiono The stream gradient is moderate, with numerous 

 good riffle areas. On the basis of bottom composition, about 30 

 percent of the stream bed might be classified as suitable spawning 

 area. Adverse factors include the high water temperatvires during the 

 summer months and the large amount of silt. Pools are adequate in 

 number, but practically without any marginal vegetation. 



There are several irrigation dams and diversions in the 

 lower part of Thief Valley Canyon, These diversions receive the 

 greatest part of the discharge from the Thief Valley Reservoir 

 Dam, 



An irrigation diversion dam is located about -^ mile above 

 the lower end of the Thief Valley Canyon, or approximately hi miles 

 above the mouth of the river» This dam is of concrete construction, 

 6 feet high, and 60 feet long. It is a b^rier to fish during low[ 

 water. Two irrigation diversions, the Duncan Ditch and the Oliver 

 Ditch, originate from either side of the dam, and each withdraws 

 30 C.foS, 



The Basche Irrigation Diversion Dam is located approximately 

 1x2^ miles above the mouth. This dam is of concrete construction, 

 3 feet high, and UO feet long. It is a barrier to fish during low 

 water, ^he ditch withdra^vs I4O c,f,s« 



The Miles Irrigation Diversion Dam is located approximately 

 UU miles above the mouth. This dam is of concrete construction, 

 3 feet high, and iiO feet long. It is a barrier to fish during low 

 water© The ditch withdraws 15 c,f ,s. 



The Thief Valley Reservoir Dam is located approximately $2 

 miles above the mouth. The U.S. Bureau of Reclamation began con- 

 struction of this dam in 1931 and completed it in 1932, It is an 

 Ambursen type dam, b^jilt entirely of reinforced concrete, and rises 

 to a height of 70 feet above the foundation. The crest length is 

 390 feet. The spillway is of the concrete overflow type, and is 

 about 268 feet long. The discharge at the time of inspection 

 (July 6, I9U2) was I60 c,f ,s«, irtiich was flowing over the top of 

 the spillway. It wqs reported by the dam tenders that the reservoir 

 level would soon be below the top of the spillway, and the discharge 



