Helix Downstream Fish Passage Design

Project ID: 3437
Principal Investigator: Leslie Hanna
Research Topic: Fish Passage and Entrainment
Funded Fiscal Years: 2015
Keywords: downstream fish passage, large dams

Research Question

Can the Helix design developed for downstream fish passage at Cle Elum Dam be easily adapted to other sites based on site-specific hydraulic criteria.

Need and Benefit

Providing access to high value spawning and rearing habit that has been cut off due to the construction of dams is a key component for the recovery of endangered fish species. Dams constructed without allowance for upstream and downstream fish passage, have resulted in the extirpation of anadromous salmon and steelhead populations in many areas. Throughout the Pacific Northwest region there is a renewed effort to provide downstream passage at main stem storage reservoirs to access this high value habitat previously accessible prior to dam construction. Storage reservoirs present many unique challenges to fish passage. The most obvious challenge is dam height, with many dams being from 100 ft to upwards of 500 ft high. Second, storage reservoirs are operated to store and release water seasonally creating reservoir water surface fluctuations of 10's or 100's of feet in a year. To date most high dams where downstream fish passage has been established are for hydropower generation facilities with minimal fluctuation in pool elevation. Generally fish passage structures at these facilities have consisted of manned surface collectors, and trap and haul methods that require very high operation and maintenance (O&M) costs.
On April 7, 2011 the NOAA Southwest Region transmitted a letter to Reclamation concerning the reasonable and prudent alternative (RPA) to comply with the recent Biological Opinion (BO), in part stating "The RPA includes a new year-round storage and temperature management program for Shasta Reservoir and the Upper Sacramento River, as well as long-term passage prescriptions at Shasta Dam and re-introduction of winter-run salmon into its native habitat in the McCloud and/or Upper Sacramento rivers."
This would require Reclamation to design and construct facilities for upstream and downstream fish passage at Shasta Dam, which is a storage reservoir with significant pool fluctuation. Similar facilities have been mentioned for other Central Valley Project dams including Folsom.
In order to retrofit existing facilities to accomodate downstream fish passage, emerging technologies such as the helix fish slide should be researched further to allow the technology to be applied successfully at other sites. Additional research is needed to reduce the high cost of implementing passage on storage reservoirs.
The Helix design now being considered for downstream fish passage at Cle Elum Dam, has the potential to be adapted for downstream fish passage at other locations. However designers need a basis for a general design (non site specific) from which to begin, and guidelines for adapting that design to meet the specific needs of a specific site.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Helix Downstream Fish Passage Design (final, PDF, 897KB)
By Jim Higgs
Publication completed on September 30, 2016

Reclamation's work on downstream fish passage for Cle Elum Dam led to the initial development of a helix design that will allow selfguided passage from a reservoir where water surface fluctuations are greater than 50 ft in elevation. Successful and extensive physical and numerical modeling from the Cle Elum project was used as a starting point for developing a more general design that can be adapted for widespread application to dam sites throughout the United States. Numerical analyses were made using FLOW-3D computational fluid dynamics software to apply the helix design to other sites where the discharge range, elevation drop, and velocity criteria requirements are different from those at Cle Elum Dam. Using the CFD modeling tools and a range of criteria, optimal helix geometry for each case study were determined.

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Last Updated: 6/22/20