The Survey 



13. Main Grande Ronde River . — (October 9-17, 19U0, Parkhurst 

 and Freyj and August 10-20, 19U1, Parkhurst, Frey, Bryant, and 

 Zimmer.) The Grande Ronde River extends for about 200 miles through 

 several physiographic regions, each having distinctive stream char- 

 acters, before reaching its source in the Blue Mountains of the Whit- 

 man National Forest in eastern Oregon. Its general direction of flow 

 is northeast. 



In the lower section the river flows for a distance of approxi- 

 mately 90 miles through a deep, narrow canyon which gradually recedes 

 upstream. Vegetation is sparse, and the stream is subject to rapid 

 fluctuations in volume. The stream had an average width of about 150 

 feet in this section on October 10, 19U0, and was discharging 698 c.f .s. 

 at a point 81 miles above the mouth, just downstream from the mouth of 

 the Wallowa River. Gaging station records of the U.S. Geological 

 Survey for the 19 year period 1926-19U5, taken at the same point, show 

 discharges ranging from a maximum of 22,UOO c.f.s. in March, 1932, to 

 a minimum of 22$ c.f.s, in December, 1935 • The average discharge at 

 the same station and for the same period was 1,867 c.f.s. The stream 

 gradient is moderate, with numerous shallow riffle areas and an ade- 

 quate number of resting pools. There are no obstructions or water 

 diversions in this lower portion of the river. There were a few silver 

 salmon spawners in the lower river at the time of the survey, but the 

 number of these fish could not be estimated because of the turbid con- 

 dition of the water. This section is capable of supporting large runs 

 of chinook and silver salmon. 



The middle portion of the river extends for a distance of about 

 60 miles, from a point 6 miles below Elgin, Oregon, up to LaGrande, 

 Oregon. In the lower part of this section the river extends for a dis- 

 tance of 6% miles through the fertile Elgin valley, which is U miles or 

 more in width and highly cultivated. This portion of the river main- 

 tains a fairly moderate gradient, and offers extensive spawning areas. 

 The river extends through a narrow, rocky gorge from 2 miles to U miles 

 above Elgin. This small canyon contains a large amount of bedrock in 

 the stream bed, and is of no value to salmon. Above the canyon the 

 Grande Ronde valley opens into an extensive floodplain 10 miles to 15 

 miles wide and about 5>0 miles long* The river meanders through this 

 flat valley section up to Island City, Oregon, 2 miles below LaGrande. 

 The gradient in this section is extremely slight, the flow often being 

 imperceptible. The stream bed is composed almost entirely of mud and 

 clay, and is worthless to migratory fish. The volume of flow in about 

 27 miles of this meandering portion of the stream is greatly reduced 

 by the State ditch, which was cut across a huge bend of the river in 

 order to prevent flooding during high water stages. There is little or 

 no flow in the slough-like portion of the river cut off by the State 

 ditch above the mouth of Catherine Creek. At the time of observation, 



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