Author(s): Denis Ruttenberg; Klaus Jorde; Peter Goodwin; Stephen Clayton; Pat Connolly
Keywords: No Keywords
Abstract: In the Upper Columbia River basin, many streams are diverted for irrigation by diversion dams, some of which are considered to block passage of endangered salmonids to spawning and rearing habitat. In Beaver Creek, a tributary to the Methow River, the U. S. Bureau of Reclamation replaced irrigation diversion dams with a series of rock vortex weirs to provide upstream passage for salmonids and maintain irrigation diversion. A monitoring program was implemented to evaluate the effectiveness of the rock vortex weirs for fish passage. Temperature, discharge, channel topography, and fish movement were monitored. Through a linear decoupled approach, a four-mode hydraulic model was developed to describe flow over the rock vortex weirs as orifice flow, gap flow, weir flow, and rough boundary flow. Using this four-mode model and field observations, rating curves for hydraulic variables important to fish passage were developed and applied to continuous flow records at the study sites, resulting in a chronological record of critical hydraulic parameters. These data were combined with records of fish passage collected by the U. S. Geological Survey's Columbia River Research Laboratory to compare hydraulic conditions to observed fish migration. Hydraulic drops during fish migration periods were estimated from 0.16 to 0.28 m, versus a guideline of 0.24 m, maximum. The ratio of pool depth to hydraulic drop ranged from 1.6 to 20, versus a guideline 1.5, minimum. Energy dissipation factors in the weir pools varied from 63 to 573 W/m3, versus a guideline of 250 W/m3, maximum. Cross section averaged velocity at the weir crest varied from 0.14 to 0.94 m/s, versus a guideline of 0.37 m/s, maximum. Based on a hydraulic analysis and recorded fish passage data, the rock vortex weirs demonstrated favorable performance in the first two years following their installation.