Aspen Journalism is compiling a data dashboard highlighting metrics of local public interest, updated weekly on Tuesdays.

This weekend’s rainfall boosted local streamflow

River levels in the Roaring Fork basin spiked on Oct. 2 as rain fell on the valley.

Below Maroon Creek, the USGS gauge measured streamflow at 176 cfs on Oct. 2, or 145.5% of average. That’s up from Sept. 25, when the river was flowing at 130 cfs, or 109.2% of average (the river was flowing at 150 cfs on Oct. 1).

At Emma, below the confluence with the dam-controlled Fryingpan, the Oct. 2 streamflow of 509 cfs represented about 120.3% of average. That’s up from 437 cfs, or 100.5% of average, on Sept. 25.

At Stillwater, located upstream of Aspen, the Fork on Oct. 2 ran at 58.1 cfs or 135.1% of average, up from 43.4 cfs or 90.4% of average, on Sept. 25. 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 1.5 cfs on Oct. 2, which was relatively unchanged from the 1.4 cfs of Sept. 25, 18 and 11.

Meanwhile, the Crystal River above Avalanche Creek, which is not impacted by dams or transbasin diversions, flowed at 146 cfs, or 137.7% of average, on Oct. 2. Last week, the river ran at 96 cfs, or 84.5% of average.

Lake Powell’s water levels remain about four feet above critical level

Lake Powell‘s storage remains at one of its lowest levels recorded since it began filling in the 1960s. On Oct. 2, the reservoir was 23.88% full (with a total capacity based on a 1986 sedimentation survey) or 24.91% full (based on 2017-18 sedimentation data), down from Sept. 25, when it was 23.91% full (1986 data) or 24.95% (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 Oct. 2, 2021, it was 29.83% full (1986 data).

On Oct. 2, Lake Powell’s elevation reached 3,529.5 feet, or 170.5 feet from full pool, slightly down from 3,529.6 feet on Sept. 25. That puts the water level just about 4.5 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. 2, the reservoir reached 3,545.33 feet, or 154.67 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 temperatures remain above normal in Aspen

High air temperatures at the Aspen airport dropped from 75°F on Sept. 26 to 68°F on Sept. 29, which is about five degrees above normal. Meanwhile, low temperatures increased from 35°F on Sept. 25 to 45°F on Sept. 29, which is about 12 degrees above normal.

‘Good’ air quality reported in Aspen last week

The air quality in Aspen was “good” last week with an AQI index for ozone ranging from 30 on Oct. 1 to 36 on Sept. 28.

Laurine Lassalle is Aspen Journalism’s data desk editor, where she works to catalogue and analyze local public data. She also heads our our “Tracking the Curve” project, documenting COVID-19 in Pitkin,...