Aspinall Unit update: Blue Mesa is expected to reach 7465 feet in elevation (400,000 af) at the end of June


Click here to read the notes from the recent operations meeting. Here’s an excerpt:

Precipitation in the Gunnison Basin in October and November, 2012 was well below 50% of normal; December precipitation was near normal. January precipitation was in 70-90% range and February dropped to 50-70%. Conditions improved in March and April with April precipitation at 150% of average to date. March and April temperatures have been below average which delays the runoff.

As of April 23rd, snowpack in the Gunnison Basin is 83% of the long-term average for that date. The current inflow forecast to Blue Mesa for April through July is 50% of the long-term average.

Blue Mesa content is now 340,583 af and has gained only 13,000 af through the winter. April 2012 content was around 533,000 af.

As of April 15th, the forecasted April-July inflow to Blue Mesa is 340,000 af, down from 370,000 af in January. 2013 falls in the Dry Year category and would be expected to be exceeded in 93% of years.

If this inflow forecast is maintained, it would represent the 5th lowest inflow since Blue Mesa was constructed (1977, 1981, 2002, and 2012 were lower).

The Black Canyon National Park peak flow will be based on the May 1 forecast; if the present forecast is maintained the peak would be 973 cfs. However, the drought provision in the water right (based on prior dry year and low Blue Mesa content) reduces this peak to 697 cfs. It is expected this flow will be achieved through normal operations; however a small increase may be necessary if conditions dictate otherwise.

Flow Recommendations call for a 900 cfs peak at Whitewater in a Dry Year based on the present forecasted inflow. Base flow targets at Whitewater are 890-900 cfs from May- August in this type year.

Under most probable conditions, Blue Mesa is expected to reach 7465 feet in elevation (400,000 af content) at the end of June which is 54 feet short of filling. By the end of the year, Blue Mesa is predicted to be 6 feet lower than the 2012 end of the year elevation.

Black Canyon flows January to April were around 300 cfs and may increase to 400-500 cfs in the summer. A peak of around 700 cfs will occur. Changing conditions always have the potential to affect these early predictions.

More Aspinall Unit coverage here and here.

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