Grand Lake Clarity

Senate Document Number 80 of the 75th Congress, 1st Session states that the C-BT project “…must be operated in such a manner as to most nearly effect…” five primary purposes, the second of which is “To preserve the fishing and recreational facilities and the scenic attractions of Grand Lake, the Colorado River, and the Rocky Mountain National Park”. 

To that end, Grand County has been working with Reclamation and other stakeholders to improve water quality conditions in Grand Lake, as water quality relates directly to the scenic attraction of the Lake. Stakeholders have agreed to utilize water clarity, as measured by Secchi depth, as the primary metric by which scenic attraction can be quantified.

In 1941, prior to completion of the C-BT project, a single Secchi depth of 9.2 meters (m) (30 feet) was measured in early September in Grand Lake. In 2007, a minimum Secchi depth of just over 1 m ( approximately 3 feet) was recorded, the lake was green, and there were concerns with cyanotoxins, which hurt local businesses. This circumstance is absolutely unacceptable for Colorado’s largest natural lake, located high in the Rocky Mountains, whose native watershed is Rocky Mountain National Park. 

To protect the lake, in 2008, Grand County, the town of Grand Lake, and Northwest Colorado Council of Governments sought a site-specific water clarity standard for Grand Lake of 4 m. While the Colorado Water Quality Control Commission approved the standard, it imposed a deferred implementation date which never went into effect. Instead, a narrative water quality standard was adopted of “The highest level of clarity attainable, consistent with the exercise of established water rights, the protection of aquatic life, and protection of water quality throughout the Three Lakes system.” (5 CCR 1002-33, Numeric Standards Table, at p. 13 (June 30, 2015)) This continues to be acceptable to the Commission and stakeholders including Grand County only because of the key MOU components, explained below.

In 2016, the Grand Lake Clarity Stakeholders Memorandum of Understanding was created “to establish an adaptive management process while Reclamation conducts a planning and NEPA process to evaluate alternatives to improve clarity in Grand Lake as described in the Clarity Supplement.” This agreement is currently in force, having begun on April 15, 2016, and it is set to expire on January 1, 2022. The “MOU may be extended by mutual agreement of Reclamation, Northern Water, and the West Slope until Reclamation issues its decision document upon completion of the NEPA…”

The MOU established water quality “goal qualifiers” that were mutually agreed upon as targets to be achieved through adaptive management during the clarity period of concern, from July 1 to September 11 each year. The goal qualifiers are an average Secchi depth during the clarity period of 3.8 meters, and minimum Secchi depth of 2.5 meters. Since adaptive management began in 2016, C-BT pumping schedules in 2018 and 2019 have led to some quite unanticipated, promising, and positive water quality outcomes.

Grand County believes it is imperative that the Clarity MOU be extended:

  • To allow adaptive management to continue, so that stakeholders can determine whether recent results can be repeated, and pumping schedules can indeed be used as a long-term means to maintain optimal water quality and clarity in Grand Lake and Shadow Mountain Reservoir.
  • To allow Reclamation to complete its planning and NEPA process to evaluate alternatives to improve clarity in Grand Lake as described in the Clarity Supplement.