The Department of the Interior will implement a spring disturbance flow at its 1,312-MW Glen Canyon Dam project March 15 to 26, 2021, to simulate a spring-timed runoff event.
The operation will coincide with required maintenance on the concrete apron downstream of the dam and powerplant. The spring disturbance flow will not affect the monthly or annual release volumes from the impounded Lake Powell, Interior said.
As the changing flows disturb river bottom habitats, ecosystem responses may include elevated algae and insect production, resulting in increased aquatic insect prey for endangered humpback chub, non-native rainbow trout and other wildlife. The flows also may affect the non-native brown trout in Glen Canyon by reducing survival of emerging young, which may help protect native fish in the river. Scientists will study the effects of the modified flows in Glen, Marble and Grand canyons, and the resulting data may be used to make future recommendations on how to better support the Colorado River ecosystem.
Releases through Glen Canyon Dam will be reduced to 4,000 cfs beginning March 15. Flows will begin a gradual increase on March 20, will peak at 20,150 cfs on March 22, and will remain steady at that level until March 25. Typical flows in March range from a daily low of 8,000 cfs to daily highs around 15,000 cfs. Standard operations will resume on the morning of March 26.
“Scientific studies like these are an important part of our obligation to effectively balance the need for water and power resources with responsible stewardship of the Colorado River ecosystem,” said the Bureau of Reclamation’s Upper Colorado Basin Regional Director Wayne Pullan. “This spring disturbance flow was developed and proposed by agency experts from the Bureau of Reclamation, U.S. Geological Survey, and Western Area Power Administration in close collaboration with Colorado River stakeholders, with strong support from environmental and recreational interests. I applaud the partnership and collaboration of the Glen Canyon Dam Adaptive Management Work Group, including all seven basin states and five Native American tribes, to continue our successful adaptive approach to managing Glen Canyon Dam.”
Reclamation is a federal agency under Interior and is the largest wholesale water supplier and second largest producer of hydroelectric power in the U.S.