Aspinall Unit operations update: 630 CFS in Black Canyon

Looking downstream from Chasm View, Painted Wall on right. Photo credit: NPS\Lisa Lynch

From email from Reclamation (Erik Knight):

Releases from the Aspinall Unit will be decreased by 100 cfs on Monday, July 23rd . Releases are being decreased to retain storage in Blue Mesa Reservoir while still reaching the baseflow target. A recent streamflow measurement has revealed that the Gunnison River at the Whitewater gage was flowing ~100 cfs higher than what the gage was reporting. The release adjustment at Crystal will bring those river flows back down closer to the baseflow target. The latest runoff volume forecast for Blue Mesa Reservoir projects 240,000 AF of inflow between April and July, which is 36% of average.

Flows in the lower Gunnison River are currently above the baseflow target of 900 cfs. River flows are expected to stay above the baseflow target for the foreseeable future.

Pursuant to the Aspinall Unit Operations Record of Decision (ROD), the baseflow target in the lower Gunnison River, as measured at the Whitewater gage, is 900 cfs for July. There is a provision in the EIS which allows the baseflow target to be reduced from 1050 cfs to 900 cfs when the content in Blue Mesa Reservoir is below 600,000 AF. The current content of Blue Mesa Reservoir is 427,000 AF and dropping.

Currently, diversions into the Gunnison Tunnel are 1050 cfs and flows in the Gunnison River through the Black Canyon are around 730 cfs. After this release change Gunnison Tunnel diversions will still be 1050 cfs and flows in the Gunnison River through the Black Canyon will be around 630 cfs. Current flow information is obtained from provisional data that may undergo revision subsequent to review.

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