Aspinall Unit update: Estimated target of 6,800 cfs high flow regime in the Gunnison Gorge and Black Canyon

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Here’s the high-flow regime planned for the Black Canyon and Gunnison Gorge this week from email from Reclamation (Dan Crabtree):

Reclamation will be operating the Aspinall Unit to allow the one day Black Canyon water right peak target flow of 6,800 cfs to be met during the next two weeks. Releases from Crystal Reservoir will ramp up from the current release of 3,500 cfs beginning Friday, June 3rd. Crystal Reservoir should begin to spill sometime Saturday June 4th. While spilling, natural fluctuations will be seen in the river system making it difficult to predict and control downstream flows. However, below is a table showing estimated flows in the Black Canyon and Gunnison Gorge below the Gunnison Tunnel. These flows should reach a peak of about 6,800 cfs on June 8th and return to about 3,200 cfs around June 13th. During this operation, combined flows of the mainstem Gunnison, North Fork and other tributaries may result in flows of around 13,000 cfs in the Delta area. Again, this schedule is an estimate and may be modified due to changing hydrologic conditions in the Gunnison basin. Further updates will be conveyed as changes occur…

Date: Flow below Gunnison Tunnel (cfs)
June 3: 3,000
June 4: 3,500
June 5: 4,500
June 6: 5,500
June 7: 6,900
June 8: 6,900
June 9: 5,900
June 10: 5,000
June 11: 4,300
June 12: 3,750
June 13: 3,150

Here’s an article from a couple of years ago explaining the high flow regime, from Mark Jaffe writing for The Denver Post. From the article:

The stronger flow is intended to mimic natural spring runoff, removing sediment and algae and helping to break down riffles and whisk away vegetation encroaching on the riverbank, Dale said…

“This has been one of the longest, most complex water-right battles in Colorado,” said Drew Peternell, an attorney for the sportsmen’s group Trout Unlimited. To win that right, the concerns of hydropower agencies, ranchers and farmers — and downstream towns fearful of flooding — had to be addressed.

More Aspinall Unit coverage here and here.

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