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

The Fork’s streamflow dropped after transbasin diversion restarted

Transbasin diversion resumed last week slowing down local streamflows. At Stillwater, located upstream of Aspen, the Roaring Fork River ran at 194 cfs on July 2, down from last week when the river ran at 559 cfs, or 138% of average.

This drop in streamflow is due to the Twin Lakes Tunnel diversion resuming on June 27. The tunnel that sends Roaring Fork flows east of the Continental Divide was running as high as 365 cfs on June 29 before dropping to 253 cfs on July 2.

The USGS sensor below Maroon Creek recorded the Fork running at 1,020 cfs on July 2, or 120.4% of average, down from 1,520 cfs, or 187.9% of average, on June 25.

At Emma, below the confluence with the dam-controlled Fryingpan, the July 2 streamflow of 1,640 cfs represented about 106.5% of average. That’s down from 2,190 cfs on June 25, or 128.1% of average.

Meanwhile, the Crystal River above Avalanche Creek, which is not impacted by dams or transbasin diversions, flowed at 1,400 cfs or 138.6% of average. Last week, the river ran at 1,570 cfs, or 130.8% of average.

The Colorado River ran at 9,790 cfs at Glenwood Springs, or 122.8% of average, on July 2, up from 13,000 cfs last week, while the Colorado flowed at 17,300 cfs near the Colorado-Utah stateline, or 147.9% of average.

Aspen Journalism is compiling real time streamflow data. You can find all the featured stations from the dashboard with their real-time streamflow on this webpage.

Lake Powell keeps filling

Lake Powell‘s water levels began their seasonal rise in mid-March as warming temperatures initiated snowmelt, after the reservoir in the winter dropped to its lowest level on record since filling. On July 2, the reservoir was 39.56% full (with a total capacity based on a 1986 sedimentation survey) or 41.27% full (based on updated 2017-18 sedimentation data). That’s up from June 25, when the nation’s second-largest reservoir was at 38.66% of capacity (1986 data) or 40.33% (based on 2017-18 data).

Last year, on July 1, 2022, 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.

On July 2, 2022, the reservoir was 26.47% full (based on 1986 data) or 27.61% (based on 2017-18 data).

On July 2, Lake Powell’s elevation reached 3,584.1 feet, or 115.9 feet from full pool, up from 3,581.4 feet on June 25. Last year, on July 2, the reservoir reached 3.539.82 feet in elevation, or 160.18 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 close to normal

High air temperatures at the Aspen airport remained above 73°F in the second half of June, up to 81°F on June 26, or about four degrees above normal. Meanwhile, low temperatures ranged between 36°F and 45°F in the past two weeks.

Clean air in Aspen last week

The air quality in Aspen was “good” last week. The AQI index for ozone ranged from 38 on June 29 to 39 on July 2.

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,...