The Survey 



9* Main Clearwater River *— (September 15-23, 1938} Hanavan 

 and Wilding*) The main Clearwater River extends for approximately 

 75 miles to the town of Kooskia, Idaho, where it is formed by the 

 confluence of the middle and south forks. The river was 900 feet 

 wide at the mouth and 300-UOO feet wide throughout most of its 

 course • Gaging station records for the years 1926 to 19U8 taken 

 at Spalding, Idaho, approximately 12 miles above the mouth, show 

 discharges ranging from a maximum flood of 177,000 c.f.s. in May, 

 19U8, to a minimum of less than 500 c.f.s. in January, 1937* The 

 average discharge for a 19 year period (1926-19U5) was 13,720 c.f.s* 

 according to U.S. Geological Survey records. The water temperature 

 ranged from 66 F. to 7h F* at the time of the survey. The gradient 

 is moderate throughout most of the course* The south fork dis- 

 charges a considerable amount of mining silt into the main Clear- 

 water, and part of this material settles to the bottom as the 

 stream gradient decreases in the lower section, forming a heavy 

 layer of silt during the low water period* The effect of this 

 deposit upon salmon is not known. There were approximately 380,000 

 sq. yd* of suitable spawning area in the main stream constituting 

 7 percent of the stream bed* 



The diversion dam of the Washington Water Power Company is 

 located approximately U miles above the mouth, and is about UO feet 

 high* The fish ladder at this dam as originally constructed was 

 ineffective for Chinook salmon because of its poor location at the 

 extreme end of the dam where there was little attraction for fish, 

 and also because at low water stages the river channel was almost 

 dry from the diversion dam to the power plant tailrace approximately 

 l£ miles downstream* The operation of this dam for 13 years without 

 adequate provision for the passage of fish is responsible more than 

 any other single factor for the present depletion of the salmon runs 

 in the Clearwater River system* An additional ladder was constructed 

 at the diversion dam in 19U0, and a ladder also was built from the 

 tailrace to the forebay of the power plant* During the period of the 

 operation of the dam before these improvements were made only the 

 lower 2\ miles of the river, containing less than 2 percent of the 

 total suitable spawning area in the entire main stream, were avail- 

 able at low water stages. 



The Clearwater has great potential value as an anadromous 

 fish producer, which could be realised if the fi3hways in conjunction 

 with the Clearwater dam were further improved and if the area were 

 restocked* 



9A* Potlatch Creek .— (Sept. 10-18,1938; Parkhurst and Morton.) 

 Potlatch Creek enters the main Clearwater River approximately 1$ 

 miles above the mouth. The stream is about 50 miles long, of which the 

 lower 22-| miles were surveyed. Above the terminus of the survey the 

 stream bed is composed largely of bedrock and boulders, the gradient 

 becomes steep, and there is little spawning area. The stream had an 



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