Glen Canyon Dam Adaptive Management Program

Current Focus

Cool Mix Flows Underway

The Bureau of Reclamation has started releasing colder water from the depths of Lake Powell through Glen Canyon Dam to disrupt the establishment of smallmouth bass, which pose a threat to populations of the federally protected humpback chub below the dam.

The 'cool mix' alternative, which is the preferred alternative in the final environmental impact statement and Record of Decision, consists of releasing water from both the penstocks and river outlet works. The intakes for the river outlet works are located approximately 100 feet below those for the penstocks and can release cooler water downstream. The minimum amount of water needed will be released through the river outlets to meet the water temperature objective.

Read the full press release here

Record of Decision - Glen Canyon Dam/Smallmouth Bass Future Flow Options and High-Flow Experimental Protocol

Reclamation has finalized it National Environmental Policy Act analysis of flows from Glen Canyon Dam to protect the humpback chub and other native fish species with the signing of a Record of Decision Link is to a PDF file for the Glen Canyon Dam Long-Term Experimental and Management Plan (LTEMP) Final Supplemental Environmental Impact Statement (SEIS) Link is to a PDF file . The LTEMP SEIS supplements the 2016 LTEMP Final Environmental Impact Statement (FEIS) and Record of Decision Link is to a PDF file and analyzes various flow options from Glen Canyon Dam to help disrupt the establishment of nonnative fish, primarily smallmouth bass, below the dam in the Colorado River.

Reclamation is also making adjustments to the high flow experiment (HFE) sediment accounting period and implementation window. These changes adjust the semiannual sediment accounting period to an annual period, with the option to implement a spring or fall HFE release, or both.

Preferred Alternative

For 2024, Reclamation selected the Cool Mix Alternative, identified in the Final SEIS as both the preferred alternative and the environmentally preferred alternative. For potential flow-based actions to address smallmouth bass after 2024 (if warranted based on temperature targets), Reclamation will consider the Cool Mix Alternative along with the other action alternatives described in the 2024 LTEMP SEIS, and will make implementation decisions from 2025 to 2027 based on future actual conditions.

Additional Resources

• Modeling the Impacts of Glen Canyon Dam Operations on Colorado River Resources Link is to a PDF file

Questions

For further information, contact the project manager by email at: LTEMPSEIS@usbr.gov for more information.