West Fork Walker River, Yerington, NV

This project was initiated by local landowners in cooperation with USFWS to address habitat concerns along the Walker River.  The exceptional trout fishery through the upstream canyon deteriorates rapidly as the river enters the agricultural valley south of Yerington, NV.   Most of the decline in habitat is due to past management and channel alterations that leave the West Fork of the Walker River over-widened, shallow, warm, and susceptible to lateral erosion.

Landowners on the Cottonwood Ranch recognized these issues and worked with USFWS to address the resource problems.  StreamWise was asked to suggest methods to improve habitat features and reduce the lateral instability through the property.  The following are photographs that depict rock structures used to deflect flows away from eroding banks, narrow the river width to improve velocity, create habitat scour holes below the rocks, and enhance trout fishing opportunities.

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Walker River at Cottonwood Ranch below bridge prior to structure.   Oct. 2007

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Same site following W-Weir placement.   Oct. 2007

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Close-up view of W-Weir below bridge.  2007

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2006 Cross-Vane structure at lower property working to center flows.  2008

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Lateral erosion typical along W. Fork Walker River south of Yerington, NV.  (Fence line was originally constructed along the right bank of the river prior to flood events.)  1996 Photo

West Fork Walker River Irrigation Take-Out Project

This project was constructed just upstream of the Cottonwood Ranch at the mouth of the canyon and was designed to facilitate irrigation diversion without impeding fish passage.  The W-Weir rock structure diversion is based on specifications by Dave Rosgen, of Wildland Hydrology.  The rock placement has several advantages over the traditional concrete check dam.

1. The rock structure allows for free passage of fish in both directions.
2. The W-Weir design centers flow lines, preventing the lateral erosion common to horizontal check dams.
3. The sluice-gate installed near the diversion opening allows for efficient by-pass of sediment at high flows, reducing annual maintenance time.
4. The scour holes created by the convergent flows below the rocks provide excellent holding habitat for fish.
5. The rock structure design passes coarse sediment efficiently, rather than retaining sediment behind the concrete structure.
6. Aesthetics and natural hydrologic function are greatly enhanced.
7. Cost for installation is a fraction of dam construction.

The following photos depict the project features.

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Survey of cross-section at proposed weir site.  2007

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Diversion intake placed on left bank prior to rock structure construction.  2008

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Weir construction in Feb. 2008.

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Completed W-Weir backing water into diversion chute.  Feb. 2008

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