Background: The Three Lakes

Granby Reservoir, Shadow Mountain Reservoir and Grand Lake – known as the Three Lakes – are part of the Colorado-Big Thompson Project’s water collection system in the Upper Colorado River basin.

Water quality in the Three Lakes became a focus in 2008 after the first phase of the Nutrient Project, an initial effort to scope nutrient-related issues in the C-BT Project. The Nutrient Project determined there was a need to investigate nutrient loading and nutrient sources into the Three Lakes.
One catalyst for the Nutrient Project was a severe algae bloom in Grand Lake in 2007, which came after the fall 2006 Shadow Mountain drawdown to control aquatic weeds, which caused additional nutrient loading to the system. The algae bloom led Grand Lake homeowners to contact local, state and federal agencies.

Also in 2008, the Colorado Water Quality Control Commission adopted a numerical clarity standard for Grand Lake that will come into effect in 2015 unless a more appropriate numerical standard can be established. Data show that the 4-meter Secchi depth standard is not possible to attain under existing conditions.
The commission also adopted nutrient criteria in 2012 that will become effective in the Three Lakes in 2015. Existing data show that the proposed criteria will likely be met.

Collaborating Agencies

The Three Lakes Technical Committee formed in 2008 with the initial task of studying nutrient loading – not necessarily water quality in more general terms – in Grand Lake, Shadow Mountain and Granby Reservoir. As the focus on clarity in Grand Lake intensified, the committee’s responsibilities expanded to include water quality, including clarity in Grand Lake.

Rather than serving as a stakeholder group, the committee focuses on technical issues and includes representatives from Colorado Parks and Wildlife, the Colorado Water Quality Control Division, Fort Collins, Grand County, the Grand County Water Information Network, the Three Lakes Association (recently merged with the Greater Grand Lake Shoreline Association), Hydros Consulting, Northern Water, the Northwest Colorado Council of Governments, the U.S. Forest Service, the U.S. Geological Survey, the U.S. Bureau of Reclamation, the U.S. Environmental Protection Agency and the Western Area Power Administration.

 Grand Lake Clarity Brochure
 Water Quality Program Brochure

Issues We Are Studying

The first phase of the Nutrient Project and subsequent studies identified issues worthy of further investigation:
  • Algae blooms in Shadow Mountain and Grand Lake
  • Aquatic vegetation in Shadow Mountain
  • Dissolved oxygen levels in Shadow Mountain
  • Effects of algal productivity on aquatic life
  • Ability to meet future nutrient standards
  • Algal toxins
  • Grand Lake water quality, including clarity
  • Taste and odor for Grand Lake’s direct intakes
  • Quality of water released to the Colorado River
  • Quality of water diverted to the East Slope