Aspen Journalism is compiling a data dashboard highlighting metrics of local public interest, updated weekly on Tuesdays.
Local streams are running lower than last week
River levels in the Roaring Fork basin dropped over the last week as dry conditions returned to the region.
Below Maroon Creek, the USGS gauge measured streamflow at 132 cfs on Oct. 9, or 97.1% of average. That’s down from Oct. 2, when the river was flowing at 176 cfs, or 145.5% of average.
At Emma, below the confluence with the dam-controlled Fryingpan, the Oct. 9 streamflow of 376 cfs represented about 92.8% of average. That’s down from 509 cfs, or 120.3% of average, on Oct. 2.
At Stillwater, located upstream of Aspen, the Fork on Oct. 9 ran at 19 cfs or 44.2% of average, down from 58.1 cfs or 135.1% of average, on Oct. 2. That put the river below the decreed minimum instream flow for the stretch of 35 cfs.
The transbasin diversion tunnel that sends Roaring Fork headwaters to Front Range cities was flowing at 22.4 cfs on Oct. 9. Last week, it ran at 1.5 cfs on Oct. 2, but diversion through the tunnel started back up on Oct. 4 and peaked on Oct. 5 at 58.6 cfs.
Meanwhile, the Crystal River above Avalanche Creek, which is not impacted by dams or transbasin diversions, flowed at 103 cfs, or 94.5% of average, on Oct. 9. Last week, the river ran at 146 cfs, or 137.7% of average.
Lake Powell’s water level has gained about one foot since last week
Lake Powell‘s storage remains at one of its lowest levels recorded since it began filling in the 1960s. On Oct. 9, the reservoir was 24.09% full (with a total capacity based on a 1986 sedimentation survey) or 25.13% full (based on updated 2017-18 sedimentation data). That’s up from Oct. 2, when the nation’s second-largest reservoir was at 23.88% of capacity (1986 data) or 24.91% (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. 9, 2021, it was 29.78% full (based on 1986 data).
On Oct. 9, Lake Powell’s elevation reached 3,530.4 feet, or 169.6 feet from full pool, just shy of one foot up from 3,529.5 feet on Oct. 2. The increase — meaning more water flowed into Powell than was released through the Glen Canyon Dam — is 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. 9 was about 5.4 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. 9, the reservoir reached 3,545.16 feet in elevation, or 154.84 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 dropped at the beginning of October
High air temperatures at the Aspen airport dropped from 75°F on Sept. 26 to 58°F on Oct. 1, which is about four degrees below normal. Meanwhile, low temperatures increased from 35°F on Sept. 25 to 45°F on Sept. 29, which is about 12 degrees above normal, before going down to 33°F on Oct. 1, which is close to the normal of 32.8°F.
Clean air reported in Aspen last week
The air quality in Aspen was “good” last week with an AQI index for ozone ranging from 34 on Oct. 3 to 43 on Oct. 10.
- Colorado’s Division of Water Resources
- Bureau of Reclamation
- Aspen Consolidated Sanitation District
- Aspen Global Change Institute