# Grand Canyon, Colorado River Flows - March, April, & May



## GCPBA (Oct 22, 2009)

*Grand Canyon, Colorado River Flows - March, April, and May
*
This is a March 14, 2018, update from Paul Davidson at Glen Canyon Dam.

The release volume from Glen Canyon Dam for March, 2018, will be 800,000 acre-feet. Hourly releases during March, 2018, are anticipated to fluctuate between approximately 7,200 cfs in the nighttime and 16,000 cfs in the daytime.

The anticipated release volume for April, 2018, is 705,000 acre-feet with daily fluctuations between approximately 8,650 cfs in the nighttime and 15,000 cfs in the daytime.

The anticipated release volume for May, 2018, is 705,000 acre-feet with daily fluctuations between approximately 7,050 cfs in the nighttime and 13,390 cfs in the daytime.

In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 MW of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of up to about 1,200 cfs above or below the hourly scheduled release rate. Under system normal conditions,  fluctuations for regulation are typically short lived and generally balance out over the hour with minimal or no noticeable impacts on downstream river flow conditions.

Releases from Glen Canyon Dam can also fluctuate beyond scheduled releases when called upon to respond to unscheduled power outages or power system emergencies. Depending on the severity of the system emergency, the response from Glen Canyon Dam can be significant, within the full range of the operating capacity of the power plant for as long as is necessary to maintain balance in the transmission system. Glen Canyon Dam currently maintains 27 MW (approximately 800 cfs) of generation capacity in reserve in order to respond to a system emergency even when generation rates are already high. System emergencies occur fairly infrequently and typically require small responses from Glen Canyon Dam. However, these responses can have a noticeable impact on the river downstream of Glen Canyon Dam.

The operating tier for water year 2018 was established in August 2017 as the Upper Elevation Balancing Tier, with an initial water year release volume of 8.23 maf and the potential for an April 2018 adjustment to equalization or balancing releases. Based on the current forecast, an April adjustment to balancing is projected to occur and Lake Powell is currently projected to release 9.0 maf in water year 2018. This projection will be updated each month throughout the water year. Reclamation will schedule operations at Glen Canyon Dam to achieve as practicably as possible the appropriate total annual release volume by September 30, 2018.

Paul Davidson, Hydraulic Engineer, Glen Canyon Dam

Bureau of Reclamation 125 S. State St. Salt Lake City, UT 84138 Ph: 801-524-3642


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