Glen Canyon Dam Update 8,000cfs Low Flow Schedule

The release volume from Glen Canyon Dam for May 2009 will be 600,000 acre-feet. Hourly and daily average releases from Glen Canyon Dam for May 2009 will be scheduled through Western Area Power Administration to be consistent with the Glen Canyon Dam Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997) and to also achieve, as nearly as is practicable, this monthly volume.

 

We anticipate the release volume for June 2009 will be 625,000 acre-feet. This will be confirmed in a subsequent directive toward the end of May. 

 

 

Over the Memorial Day weekend, contractors working for the Grand Canyon Monitoring and Research Center (GCMRC) will be collecting airborne data (LIDAR and digital image data) to support the long-term monitoring of the Grand Canyon and to evaluate the effects of the March 2008 high flow experiment. Steady flows of 8,000 cubic feet per second (cfs) will be needed for this effort.

 

Airborne data collection will begin on Friday May 22, 2009. However, in order for flows to be stabilized in the Grand Canyon, the 8,000 cfs release will need to begin on Thursday May 21, 2009.   Releases from Glen Canyon Dam will be reduced to 8,000 cfs by 1800 hours on Thursday May 21, 2009. The normal down ramp rate of 1,500 cfs per hour will be used to reach this 8,000 cfs release. Releases will then be held at 8,000 cfs until Wednesday May 27, 2009 at 0600 hours when a load-following pattern consistent with the Glen Canyon Dam Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997) will be reestablished. Attached to this notification is a pdf file showing the average hourly releases scheduled for each hour of the steady flow period.

 

GCMRC has indicated that depending upon weather conditions and other factors, the data collection may be completed in less time, or possibly may require more time than in the schedule outlined above. It may be possible to return to a load following pattern as soon as Monday May 25, 2009. Additionally, weather conditions may require an extension of the steady 8,000 cfs releases. The steady 8,000 cfs releases could be extended up to three additional days to complete the data collection mission. I will be in communication with Phil Davis from GCMRC over the Memorial Day weekend. I will relay specific information to Western and the Glen Canyon Control Room on any required modifications to the duration of the 8,000 cfs steady release.

 

While scheduled releases will be steady at 8,000 cfs, load control (AGC) will be maintained at Glen Canyon Dam for the duration of this special release.