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DEQ releases water quality improvement plan reviews for three Idaho water bodies 

November 17, 2022

Contact: Thea Wickersham, Water Quality Coordinator, 

BOISE — The Idaho Department of Environmental Quality (DEQ) is releasing three water quality improvement plan reviews—known as five-year reviews—which assess conditions in the Fernan Lake Watershed, Kootenai and Moyie River Subbasin, and Salmon Falls Creek Subbasin. 

The five-year reviews are intended to evaluate current water quality improvement plans (called a total maximum daily load or TMDL), which are currently in place for the three water bodies. The five-year reviews also evaluate whether the pollution-reduction goals are still appropriate and if any adjustments need to be made. 

Kootenai and Moyie River Subbasin  

The Kootenai River subbasin is in the North Idaho panhandle. In 2019, two water bodies representing seven segments of the subbasin were listed as impaired due to temperature exceedances. 

On June 29, 2022, DEQ conducted a review of the available data and presented findings to the Kootenai/Moyie Watershed Advisory Group. In its assessment, DEQ recommended increasing shade allocations from 0% to 58% to reduce temperature and determined that the current sediment loading reductions are effective. DEQ also recommended developing additional pollutant reduction plans to control selenium pollution. 

The 2019 and 2022 plans will result in measurable water quality improvements throughout the subbasin, including an increase in shade, decrease in sediment loads, and expanded wildlife habitat. DEQ is conducting additional monitoring for selenium concentrations in fish tissue and the water column to help inform future protection efforts. 

  • DEQ regional contact: Todd Higens, Watershed Analyst, 

Fernan Lake Watershed 

Fernan Lake covers 381 acres in the northern area of the Coeur d’Alene Lake subbasin and is a popular destination for boating, fishing, and swimming. 

The lake is currently not supporting its recreation beneficial use due to elevated phosphorus levels, which has led to recurring harmful algal blooms during the summer months. In 2013, DEQ developed a TMDL to reduce total phosphorus loads in Fernan Lake, with the goal of reducing the frequency of blooms.  

In 2022, DEQ prepared a five-year review to assess the appropriateness of the 2013 TMDL. The review determined that the timeframe for achieving pollution-reduction objectives and restoring the lake’s recreation beneficial use is 20 years and, based on the implementation plan actions, the 2013 TMDL is appropriate and attainable. 

Over the last several years, organizations and agencies such as Ducks Unlimited Inc., US Forest Service, University of Idaho Cooperative Extension, Natural Resources Conservation Service, and Kootenai-Shoshone Soil and Water Conservation District have implemented water quality improvement projects in Fernan Lake Watershed. Moving forward, DEQ will continue working with local partners to restore nutrient balance in Fernan Lake. 

  • DEQ regional contact: Lily Conrad, Watershed Analyst, 

Salmon Falls Creek Subbasin 

The Salmon Falls Creek Subbasin in south central Idaho discharges into the Snake River just south of Hagerman, Idaho. Its two main reservoirs—Salmon Falls Creek Reservoir and Cedar Creek Reservoir—are popular year-round recreation and fishing spots. 

Sediment, nutrients, and temperature are the most common pollutants throughout the subbasin. DEQ first developed a TMDL for the water body in 1997, followed by several assessments and updates in 2001, 2007, 2009, and 2021. 

In 2022, DEQ’s Twin Falls Regional Office released an updated five-year review and determined that the current TMDL targets remain effective and that overall pollutant levels in the subbasin are improving. Total phosphorus levels remain above current targets, total nitrogen falls within the target range but still needs improvements, and total suspended solids are below the target in both upper and lower portions of the drainage system.  

DEQ is continuing to implement best management practices throughout the drainage area to reduce pollutant loading, including working with landowners to construct wetlands, restore streambanks, protect riparian buffers, and establish livestock watering facilities separate from the stream areas. 


The Idaho Department of Environmental Quality (DEQ) is responsible for reviewing and re-evaluating each total maximum daily load (TMDL), according to Idaho Code §39-3611(7). This includes determining the appropriateness of TMDL targets, pollutant allocations, and assumptions, as well as evaluating whether the water quality criteria identified in the TMDL are consistent with current water quality standards. 

Five-year reviews address water bodies that are impaired or threatened, but a TMDL is already completed or not required. The five-year review process may also recommend delistings or revisions. 

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