Three Lakes Nutrient Study

Lake Granby, Shadow Mountain Reservoir and Grand Lake are part of the C-BT Project's West Slope collection system in the Upper Colorado River basin.

As part of the Nutrient Project, the Three Lakes Nutrient Study incorporates the project’s Phase 1 recommendations regarding nutrient loading to the three lakes.

The Three Lakes Nutrient Study's objectives are to characterize nutrient loading, identify nutrient sources and develop methods to decrease nutrient loading without decreasing C-BT Project yield.

The Nutrient Project’s first phase identified these nutrient-related concerns:

  • Algae blooms
  • Aquatic vegetation 
  • Effects of algal productivity on aquatic life
  • Ability to meet future nutrient standards
  • Algal toxins
  • Grand Lake water quality
  • Taste and odor problems for Grand Lake's direct water intakes
  • Quality of water released to the Colorado River

Recently, algae blooms in Shadow Mountain Reservoir and Grand Lake have increasingly worried local homeowners, Grand County officials, state and federal agencies, Northern Water and C-BT water users. 

Water Quality Model
The three lakes water quality model is a pivotal element of the Three Lakes Nutrient Study. It is also important for the Grand Lake Clarity Project.

In 2009 a team of modeling experts gathered to review existing three
lakes water quality models and recommend future work. The modeling team includes representatives of Hydros Consulting, the U.S. Geological Survey, the U.S. Bureau of Reclamation and the Tahoe Environmental Research Center.

As a result of the modeling team's recommendations, in 2010 Northern Water increased its water quality data collecting efforts, and Hydros, Inc. revised the three lakes water quality model. The Three Lakes Technical Committee and the modeling team approved the revised model in the summer of 2011. The model is now being used to:

  • Analyze nutrient loading sensitivities (how water quality changes with nutrient reductions)
  • Establish a nutrient budget (determine all nutrient contributions)
  • Examine the relationship between C-BT Project operations and water quality
  • Evaluate alternatives to improve water quality
Grand Lake, Shadow Mountain Reservoir, Lake Granby
The Three Lakes Technical Committee studies nutrient loading in
(left to right) Grand Lake, Shadow Mountain Reservoir and Lake Granby.

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Three Lakes Technical Committee Formed in 2008, the Three Lakes Technical Committee studies nutrient loading in Grand Lake, Shadow Mountain Reservoir and Lake Granby, and provides technical assistance and review. Committee members are also involved with the Grand Lake Clarity Project.

The committee includes representatives from the Colorado Division of Wildlife, the Colorado Water Quality Control Division, the City of Fort Collins, Grand County, the Grand County Water Information Network, Hydros Consulting, Northern Water, the Northwest Colorado Council of Governments, the U.S. Geological Survey, the U.S. Bureau of Reclamation and the U.S. Environmental Protection Agency. 

Focus on Technical Issues
Rather than a stakeholder group, the committee focuses on technical issues, including:
  • Characterizing nutrient loading
  • Identifying nutrient sources
  • Developing strategies to decrease nutrient loading (if deemed necessary and feasible by the committee)

Contact Esther Vincent, Water Quality Manager
at (970) 622-2356 or