Middle Eighteenmile Ellsworth

The Lemhi Soil and Water Conservation District (LSWCD) worked with the Ellsworth Angus Ranch to implement the Middle Eighteenmile Ellsworth habitat project for the benefit of Chinook salmon (Oncorhynchus tshawytscha) and steelhead (Oncorhynchus mykiss) in 0.33 mile of Eighteenmile Creek, a headwater tributary to the Lemhi River. This portion of stream had been moved from the original channel into a straightened homogeneous riffle to accommodate irrigation and hay production.

Habitat actions included construction of new channel with meanders, pools and floodplain, wetland sod bank installation, instream willow rootball and bank treatments (shown under ‘other engineered structures’ in metrics), riparian plantings, livestock exclusion fence, and a hardened water gap.

Note this project was originally funded from grants FY17 ($79,747) and FY20 ($30,263); when sufficient funds became available in the FY17 grant year due to another project being terminated, this project was fully funded from the FY17 grant.

Engineered features built instream provide a diverse suite of habitat conditions for juvenile fish summer rearing and overwintering, such as improved riparian and floodplain conditions, stream temperature regulation, and a reduction in sedimentation. Instream fish habitat features include deeper pools with cooler water and more vegetative cover, fewer continuous shallow riffles, and more instream small woody debris. The surrounding floodplain was reactivated to create a hyporheic exchange between surface water and groundwater to lower water temperatures in the summer months and slightly warm water temperatures in winter. The winter groundwater exchange in the riparian zone will help reduce detrimental anchor ice.