Aspen Journalism is compiling a data dashboard highlighting metrics of local public interest, updated weekly on Tuesdays.
Out-of-state wildfires worsen local air quality
The air quality in Aspen worsened over the past week due to out-of-state wildfires. On Sept. 12, the Colorado Department of Health and Environment noted that smoke concentrations were increasing especially along the northern Front Range, and that “(h)azy skies and light to moderate concentrations of smoke are possible in northern and western portions of Colorado, due to smoke from out-of-state wildfires.”
The AirNow Fire and Smoke map shows that several large wildfires burning across the West, including major fires in northern and southern California, and a 11,700-acre fire in central Utah. In Aspen, air quality was “moderate” for three consecutive days last week as the AQI index for PM 2.5 rose to 54, 69 and 56 on Sept. 6-8. Air quality was then “good’ on Sept. 9 but went back to “moderate” on Sept. 10 with an index of 62.
In comparison with last year, Aspen has had fewer “moderate” air quality days between Aug. 14 and Sept. 11. In 2021, Aspen counted 15 days with “moderate” air quality during that stretch, while only four days reported a “moderate” air quality between Aug. 14 and Sept. 11, 2022. It’s worth noting that there were 20 days of moderate air quality in the spring and early summer in 2022, but that since Aspen Journalism’s daily air quality data collection began on Aug. 14, 2021, we are not not drawing comparisons here to any air quality data before that date.
Local rivers and streams are flowing below average
Streamflows along the Roaring Fork River this late summer season are generally dropping, though the river’s upper section is much more dependent on what’s happening with the Independence Pass transbasin diversion system.
Below Maroon Creek, the USGS gauge measured streamflow at 123 cfs on Sept. 11, or 87.2% of average. That’s down from Aug. 28, when the river was flowing at 162 cfs at 105.9% of average
At Emma, below the confluence with the dam-controlled Fryingpan, the Sept. 11 streamflow of 419 cfs represented about 89.3% of average. That’s down from 509 cfs, and 104.1% of average, on Aug. 28.
At Stillwater, located upstream of Aspen, the Fork on Sept. 11 ran at 36.3 cfs or 75.6% of average, up from 24.9 cfs and from 48.8% of average, on Aug. 28. That put the river above the decreed minimum instream flow for the stretch of 35 cfs.
The transbasin diversion that sends Roaring Fork basin headwaters to Front Range cities was flowing at 1.4 cfs on Sept. 11. The Cameo call, which curtails the Independence Pass diversions in favor of senior Grand Valley water rights, came back on Sept. 4. On Sept. 1, the tunnel to Twin Lakes was diverting about 20 cfs.
Meanwhile, the Crystal River above Avalanche Creek, which is not impacted by dams or transbasin diversions, flowed at 77 cfs, or 62.4% of average, on Sept. 11. Two weeks ago, the river ran at 143 cfs, or 103.6% of average.
Lake Powell’s elevation drops to five feet above critical level
Lake Powell‘s storage remains at one of its lowest levels recorded since it began filling in the 1960s. On Sept. 11, the reservoir was 24.03% full (with a total capacity based on a 1986 sedimentation survey) or 25.06% full (based on 2017-18 sedimentation data), down from Aug. 28, when it was 24.56% full (1986 data) or 25.62% (2017-18 data).
On July 1, the Bureau of Reclamation revised its data on the amount of water stored in Lake Powell, with a new, lower tally taking into account a 4% drop in the reservoir’s total available capacity between 1986 and 2018 due to sedimentation.
“After inputting the new data on July 1, 2022, storage values at the current elevation were updated, resulting in a decrease of 443,000 acre-feet,“ bureau officials wrote in an email.
Aspen Journalism published a story explaining the recent drop in storage due to sedimentation.
The reservoir’s capacity has fallen since last year, when on Sept. 11, 2021, it was 30.71% full (1986 data).
On Sept. 11, Lake Powell’s elevation reached 3,530.3 feet, or 169.9 feet from full pool, down from 3,532.2 feet on Aug. 28. That puts the water level just five feet above the target elevation of 3,525. Powell’s surface elevation this year peaked at 3,539.84 feet on July 3, after it dipped to its lowest level since filling of 3,522.24 on April 22. Last year, on Sept. 11, the reservoir reached 3,548.38 feet, or 151.62 feet from full pool.
The “minimum power pool” for turbines generating hydropower at the Glen Canyon Dam is 3,490 feet, and 3,525 feet has been set as a buffer to ensure that the reservoir and the turbines can continue to function properly.
Air temperature reaches up to 15 degrees above normal
High air temperatures at the Aspen airport rose in early September from 83°F on Sept. 1 to 87°F on Sept. 5, which is about 15 degrees above normal. Meanwhile, low temperatures were also above average. On Sept. 5, minimum temperature was hovering around 48°F, or about seven degrees above normal.
