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

Local streamflows keep dropping

Transbasin diversion resumed two weeks ago slowing down local streamflows. At Stillwater, located upstream of Aspen, the Roaring Fork River ran at 96.8 cfs on July 9, or 40% of average, down from last week when the river ran at 194 cfs, or 62.8% 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 197 cfs on July 9.

The USGS sensor below Maroon Creek recorded the Fork running at 757 cfs on July 9, or 111% of average, down from 1,020 cfs, or 120.4% of average, on July 2.

At Emma, below the confluence with the dam-controlled Fryingpan, the July 9 streamflow of 1,290 cfs represented about 105.7% of average. That’s down from 1,640 cfs on July 2, or 106.5% of average.

Meanwhile, the Crystal River above Avalanche Creek, which is not impacted by dams or transbasin diversions, flowed at 1,120 cfs or 145.8% of average. Last week, the river ran at 1,400 cfs, or 138.6% of average.

The Colorado River ran at 7,440 cfs at Glenwood Springs, or 117% of average, on July 9, up from 9,790 cfs last week, while the Colorado flowed at 10,500 cfs near the Colorado-Utah stateline, or 119.5% 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’s water levels still on the rise but at a slower pace

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 9, the reservoir was 41.49% full (based on updated 2017-18 sedimentation data). That’s up from July 2, when the nation’s second-largest reservoir was at 41.27%.

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. We will be now using the 2017-18 sedimentation data only.

On July 9, 2022, the reservoir was 27.52%.

On July 9, Lake Powell’s elevation reached 3,584.7 feet, or 115.3 feet from full pool, up from 3,584.1 feet on July 2. Last year, on July 9, the reservoir reached 3.539.48 feet in elevation, or 160.52 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 close to normal

High air temperatures at the Aspen airport dropped as low as 70°F on June 30 before going back, up to 76°F on July 1, or three degrees below normal. Meanwhile, low temperatures reached 48 °F on June 28 before dropping to 38 °F on July 1.

“Good” air quality reported in Aspen last week

The air quality in Aspen was “good” last week except on July 8 when the AQI index for ozone was “moderate” and reached 51. For the remainder of the week, the AQI index for ozone ranged from 40 on July 4 to 48 on July 6 and 9.

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,...