It is that time of the year!
BUREAU OF RECLAMATION
ASPINALL UNIT SPRING OPERATIONS
May 12, 2023
The May 1st forecast for the April – July unregulated inflow volume to Blue Mesa Reservoir is 830,000 acre-feet. This is 131% of the 30 year average. Snowpack in the Upper Gunnison Basin peaked at 138% of average. Blue Mesa Reservoir current content is 434,000 acre-feet which is 52% of full. Current elevation is 7470.4 ft. Maximum content at Blue Mesa Reservoir is 828,00 acre-feet at an elevation of 7519.4 ft.
Based on the May forecasts, the Black Canyon Water Right and Aspinall Unit ROD peak flow targets are listed below:
Black Canyon Water Right
The peak flow target is equal to 6,400 cfs for a duration of 24 hours.
The shoulder flow target is 810 cfs, for the period between May 1 and July 25.
Aspinall Unit Operations ROD
The year type is currently classified as Average Wet.
The peak flow target is currently 14,300 cfs and the duration target at this flow is currently 2 days.
The half bankfull target is currently 8,070 cfs and the duration target at this flow is currently 20 days.
Pursuant to the Aspinall Unit Operations ROD, releases from the Aspinall Unit will be made in an attempt to match the peak flow of the North Fork of the Gunnison River to maximize the potential of meeting the desired peak at the Whitewater gage, while simultaneously meeting the Black Canyon Water Right peak flow amount. The latest forecast for flows on the North Fork of the Gunnison River shows a high peak flow occurring near the middle of next week. Flows in the tributaries downstream of the North Fork confluence are also very high, which will help with meeting the flow targets on the lower Gunnison River at the Whitewater gage.
Therefore ramp up for the spring peak operation will begin on Friday, May 12th, with the intent of timing releases with this potential higher flow period on the North Fork of the Gunnison River. Releases from Crystal Dam will be ramped up according to the guidelines specified in the EIS, with 2 release changes per day, until Crystal begins to spill. The release schedule for Crystal Dam is:
Crystal Dam will be at full powerplant and bypass release on May 15th. Crystal Reservoir will begin spilling by May 16th and the peak release from Crystal Dam should be reached on May 18th. The flows in the Gunnison River after that date will be dependent on the timing of the spill and the level of tributary flow contribution. Estimates of those numbers will be determined in the upcoming days.
The current projection for spring peak operations shows flows in the Gunnison River through the Black Canyon peaking at 6400 cfs in order to achieve the desired peak flow and duration at Whitewater. Actual flows will be dependent on the downstream contribution of the North Fork of the Gunnison River and other tributaries. Higher tributary flows will lead to lower releases from the Aspinall Unit and vice versa.