Aspinall Unit operations update: Gunnison Tunnel diverting for the season

Gunnison Tunnel via the National Park Service

From email from Reclamation (Erik Knight):

Releases from the Aspinall Unit have been increasing over the last couple weeks as diversions to the Gunnison Tunnel have begun. So far these release changes have kept the flows in the Gunnison River through the Black Canyon around 630 cfs. Diversions into the Gunnison Tunnel are expected to increase again this week. This time releases from Crystal Dam will remain unchanged and Gunnison River flows will decrease accordingly. It is expected that river flows will decrease by 100-200 cfs this week. Currently snowpack in the Upper Gunnison Basin is at 72% of normal. The latest runoff volume forecast for Blue Mesa Reservoir projects 360,000 AF of inflow between April and July, which is 53% of average.

Flows in the lower Gunnison River are currently above the baseflow target of 890 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 890 cfs for April and May.

Currently, diversions into the Gunnison Tunnel are 620 cfs and flows in the Gunnison River through the Black Canyon are around 630 cfs. By the end of the week Gunnison Tunnel diversions could be in the 700 to 800 cfs range and river flows could be in the 400 to 500 cfs range. Current flow information is obtained from provisional data that may undergo revision subsequent to review.

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