Loon Creek Habitat Improvement

Salmonid Habitat Restoration and Acquisition

Fish Passage Improvement Fish Screening Instream Flow
Project ID014 18 SA
Recovery DomainsInterior Columbia
Start Date01/01/2019
End Date12/31/2022
Last Edited04/22/2022
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The Diamond D Ranch, a historic wilderness inholding that has operated as a popular summer vacation and fall hunting destination since the 1950’s, is located at the headwaters of Loon Creek, one of the largest tributaries to the Middle Fork of the Salmon River, 42 miles north of Stanley, Idaho. The Diamond D Ranch is private land located in the Frank Church River of No Return Wilderness Area. Loon Creek and its tributaries, including Trail and Mayfield Creeks, are critical spawning streams for Chinook salmon (Oncorhynchus tshawytscha) and steelhead (O. mykiss).

NFMS has identified upper Loon Creek (upstream from the Diamond D Ranch) as containing critical Chinook salmon and steelhead spawning and rearing habitat. The current 19 cfs hydropower diversion represents a limiting factor for Chinook and steelhead recovery as it reduces the quality of nearly half of a mile of Chinook and steelhead spawning and rearing habitat, and reduces access to 11.5 miles of Chinook and 24.8 miles of steelhead habitat. In response to concerns about the Loon Creek diversion and the difficulties associated with screening the diversion for 19 cfs
identified by the IDFG screen shop, the Loon Creek Land Co., in partnership with the Diamond D Ranch, has developed the following proposal to address these concerns and improve habitat and passage while continuing to use hydropower.

This project has three specific phases. Phase 1 will increase in-stream flows by 8 cfs in a dewatered section of Loon Creek above the confluence of Mayfield Creek by replacing a 100+ year old hydroelectric turbine at the Diamond D Ranch. Phase 2 will create and screen a new diversion into the private lake that supplies water to the hydro described in Phase 1. Phase 3 will remove a 22 inch penstock that crosses Loon Creek that is a barrier to fish passage, which will open 11.5 miles of habitat.

This project will be completed by a coordinated effort between the Custer Soil and Water Conservation District, The Loon Creek Land Company, The Diamond D Ranch, and Idaho Department of Fish and Game. Matching funds will be provided by The Loon Creek Land Company, The Diamond D Ranch, and Custer Soil and Water Conservation District.

Note that this project was awarded additional funds in Dec 2020 and is now multi-year funded from PCSRF FY18, FY19, and FY20.

Project Benefit    

Loon Creek and its tributaries, including Trail and Mayfield Creeks, are critical spawning streams for Chinook salmon (Oncorhynchus tshawytscha) and steelhead (O. mykiss). This project will result in increased in-stream flows in Loon Creek of approximately 8 cfs, improve fish habitat in/around the Diamond D Ranch, provide fish access to 11.5 additional miles of habitat by improving fish passage and prevent Snake River Spring/Summer-run Chinook Salmon and Snake River Steelhead from being entrained in the lake at the Diamond D Ranch by installing a NOAA criteria fish screen.


Metric Completed Originally
Fish Passage
  Barriers Removed 1
  Miles Opened 11.50
Fish Screens
  Screens Installed 1

Funding Details

In-Kind Donated Labor$69,140
In-Kind Other$144,627
Report Total:$841,129

Project Map


Diamond D Ranch    

  • Worksite Identifier: Diamond D Ranch
  • Start Date: 01/01/2019
  • End Date: 12/31/2021
Area Description
Loon Creek

Location Information

  • Basin: Salmon
  • Subbasin:
  • Watershed:
  • Subwatershed:
  • State: Idaho
  • Recovery Domain: Interior Columbia
  • Latitude: 44.55
  • Longitude: -114.85


  • Snake River Basin Steelhead DPS
  • Snake River Spring/Summer-run Chinook Salmon ESU




  • C.0 Salmonid Habitat Restoration and AcquisitionY (Y/N)
    •      . . C.0.a Habitat restoration and acquisition funding .00
    •      . . C.0.b Length of stream treated/protected
    •      . . C.0.c
      Project identified in a Plan or Watershed Assessment
    •      . . C.0.d.1 Project Monitoring (LOV)
    •      . . C.0.d.2 Monitoring Location (LOV)
    •      . . C.1 Fish Screening ProjectY (Y/N)
      •      . . . . C.1.a Fish screen funding
      •      . . . . C.1.b Quantity of water protected by screens (Acre feet/year)
      •      . . . . C.1.c.1 Fish screens installedY (Y/N)
        •      . . . . . . C.1.c.2 Number of new fish screens installed
      •      . . C.2 Fish Passage ImprovementY (Y/N)
        •      . . . . C.2.a Fish Passage Funding
        •      . . . . C.2.b.1 Length of stream made accessible
        •      . . . . C.2.b.3 Type of blockage/barrier (LOV)
        •      . . . . C.2.b.4 Number of blockages/impediments/barriers impeding passage
        •      . . . . C.2.c.1 Fish passage blockages removed or altered (other than road crossings reported in C.2.f to C.2.i)Y (Y/N)
          •      . . . . . . C.2.c.2 Number of blockages/impediments/barriers removed/altered
        •      . . C.3 Instream Flow ProjectY (Y/N)
          •      . . . . C.3.a Instream Flow Funding
          •      . . . . C.3.b Length of stream 'protected' for adequate flow
          •      . . . . C.3.c Change in water flow (cfs)
          •      . . . . C.3.d.1 Water flow gaugesY (Y/N)
            •      . . . . . . C.3.d.2 Number of water flow gauges
          •      . . . . C.3.g.1 Maintaining adequate flow or reducing withdrawalsY (Y/N)
            •      . . . . . . C.3.g.2 cfs (cubic feet per second) of water conserved per year (cfs)