Aspen Journalism is compiling a data dashboard highlighting metrics of local public interest, updated weekly on Tuesdays.
September’s 1.3 inches of rain was just below average, as measured at Aspen airport
Precipitation measured at Aspen airport was below average in September 2022, with a total of 1.3 inches compared to the 1991-2020 average of 1.43 inches, according to NOAA. August’s 2.29 inches beat the month’s average of 1.48 inches and made it the rainiest month of the year due to the monsoon rain. July’s precipitation was also above average with 1.71 inches. From June to September, more than six inches of rain fell this year, compared to a historical average of about 5.5 inches.
Streamflows up as transbasin diversion stops
River levels in the upper Roaring Fork basin went up in the last week, as transbasin diversions to the Front Range took a break.
The Roaring Fork River below Maroon Creek flowed at 150 cfs on Oct. 16, or 107.9% of average, according to the USGS gauge. That’s up from Oct. 9, when the river was flowing at 132 cfs, or 97.1% of average.
At Stillwater, located upstream of Aspen, the Fork on Oct. 16 ran at 38.5 cfs or 93.9% of average, up from 19 cfs or 44.2% of average on Oct. 9. That put the river above the decreed minimum instream flow for the stretch of 35 cfs. The river’s streamflow dropped from 62 cfs on Oct. 4 to 17.1 cfs on Oct. 13, before going back up to 38.5 cfs on Oct. 16.
The Fork’s flow was impacted by the Independence Pass transbasin diversion system that sends Roaring Fork headwaters to Front Range cities. The diversion, which was curtailed for much of September to benefit senior downstream water rights, started back up on Oct. 4 and peaked on Oct. 5 at 58.6 cfs. It ran at 22.4 cfs on Oct. 9, but stopped around Oct. 14 as water flowing through the tunnel under the Continental Divide was running at at 1.6 cfs on Oct. 16.
The Roaring Fork at Emma, below the confluence with the dam-controlled Fryingpan, saw and Oct. 16 streamflow of 363 cfs, or about 99.2% of average. That’s down from 376 cfs, but up from 92.8% of average, on Oct. 9.
Meanwhile, the Crystal River above Avalanche Creek, which is not impacted by dams or transbasin diversions, flowed at 81 cfs, or 81.4% of average, on Oct. 16. Last week, the river ran at 103 cfs, or 94.5% of average.
Lake Powell’s water level remains stable
Lake Powell‘s storage remains at one of its lowest levels recorded since it began filling in the 1960s. On Oct. 16, the reservoir was 24.06% full (with a total capacity based on a 1986 sedimentation survey) or 25.10% full (based on updated 2017-18 sedimentation data). That’s down from Oct. 9, when the nation’s second-largest reservoir was at 24.09% of capacity (1986 data) or 25.13% (based on 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. Aspen Journalism in July published a story explaining the that drop in storage due to sedimentation.
The reservoir’s capacity has fallen since last year, when on Oct. 16, 2021, it was 29.68% full (based on 1986 data).
On Oct. 16, Lake Powell’s elevation reached 3,530.3 feet, or 169.7 feet from full pool, relatively unchanged from 3,530.4 feet on Oct. 9. Last week, the reservoir gained about one foot from the prior week. The increase — meaning more water flowed into Powell than was released through the Glen Canyon Dam — was likely due to a number of factors including a drawdown in irrigation demands in the upper basin, recent rainfall and the cooling fall temperatures reducing the amount of water consumed by vegetation.
The reservoir’s water level on Oct. 16 was about 5.3 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 Oct. 16, the reservoir reached 3,544.8 feet in elevation, or 155.2 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.
Aspen recorded above-normal air temperatures so far this month
High air temperatures at the Aspen airport increased from 58°F on Oct. 1 to 66°F on Oct. 5, which is about six degrees above normal. Since then, temperatures have remained above average while slowly going down. On Oct. 13, maximum air temperature reached 62°F, or four degrees above normal. Meanwhile, low temperatures reached up to 43°F on Oct. 2 before dropping to 32°F on Oct. 5. Low temperatures have also remained close but above normal. On Oct. 13, it was down to 29°F, which is 0.1 degrees above normal.
Clean air in Aspen
The air quality in Aspen was “good” last week with an AQI index for ozone ranging from 34 on Oct. 13 to 41 on Oct. 15.
