The Survey 



Main Snake River ,— The Snake River joins the Columbia 

 River approximately 32U~miles above the mouth. It is the largest 

 tributary to the Columbia River, extending for a distance of more 

 than 1,000 miles. It flows through southeastern Washington, forms 

 part of the western boundary of Idaho, and extends through south- 

 ern Idaho to the continental divide in Wyoming, Its drrinage area 

 comprises more than 5-09,000 square miles. Gaging station records 

 for the water-years 1909-193$, taken at a station 68 miles above the 

 mouth, show discharges ranging from a maximum of 270,000 c.f.s. in 

 May to a minimum of 10,600 c.f.s. in August and September, The 

 mean discharge was 1*9,070 c.f.s. The flood of June, 189U reached 

 a crest of about U09,000 c.f.s. near the same station, and the 

 flood of May, 19U8 reached a peak of 368,000 c.f.s, near Clarkston, 

 13U miles above the mouth. The discharge at the mouth is somewhat 

 higher than these figures, but reliable data are not available. 



From the mouth to Lewis ton, Idaho, a distance of approxi- 

 mately 11*0 miles, the Snake Riv£r has a moderate gradient and some 

 extensive spawning areas. 



1. Palouse River , — (Not surveyed) The Palouse River enters 

 the Snake River approximately 60 miles above the mouth* It is a 

 large river abofct 150 miles long. A high falls located about 6 

 miles above the mouth renders the stream inaccessible to migratory 

 fish. 



2. Tucannon River .— (February 2-8,193$, and June 18-19, 193$J 

 Suomela, Shuman, and Burrows.) The Tucannon River enters the Snake 

 River approximately 63 miles above the mouth. The stream is about 

 60 miles long, of which the lower 53 miles were surveyed. Near the 

 mouth the stream had an average width of SO-60 feet. The discharge 

 at the mouth on February 2, 193$ was 180 c.f.s. Oaging-station 

 records for the period of September, 1913 through September, 191U, 

 taken at a station 2$ miles above the mouth show discharges ranging 

 from a maximum of 29h c.f.s. in April and May, to a minimum of $9 

 c.f.s. in August. The water temperature ranged from 36°F. to U3°F« 

 in February, and from U*°F. to 53°F. in June. The gradient is 

 moderate in the lower U9 miles, and becomes fairly steep in the 

 upper U miles of the section surveyed. There are numerous good 

 shallow riffles and an adequate number of resting pools well distri- 

 buted throughout the stream course. It was estimated that there 

 were 1,091,000 sq. yd. of medium and small rubble, constituting 9U 

 percent of the total bottom in the section surveyed. A significant 

 portion of the medium and small rubble constituted excellent salmon 

 spawning area. 



It is difficult for fish to enter the Tucannon River at 

 low water stages because of a delta that has been formed at the 

 mouth by flood action. This section is in need of channel improve- 

 ment. 



