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

Streamflows down from last week

Streamflows in the Roaring Fork basin are down from last week.

Aspen Journalism is now compiling real time streamflow data. At Stillwater, located upstream of Aspen, the Fork ran at 39.7 cfs on April 24 at 1:30 pm. In terms of trends, the Fork ran at 40.1 cfs or 65.7% of average on April 23 after reaching 65.6 cfs on April 19. That’s down from 55.2 cfs and 117.4% of average, on April 16.

You can find all the featured stations from the dashboard with their real-time streamflow on this webpage.

The USGS sensor on the Roaring Fork river below Maroon Creek recorded the Fork running at 138 cfs on April 23, or 98.6% of average. That’s down from 164 cfs on April 16.

At Emma, below the confluence with the dam-controlled Fryingpan, the April 23 streamflow of 364 cfs represented about 78.3% of average. That’s down from 412 cfs, and 101.7% of average, on April 16.

The transbasin diversion that sends Roaring Fork basin headwaters to Front Range cities was flowing at 13.7 cfs on April 23, up from 5.9 cfs on April 16.

Meanwhile, the Crystal River above Avalanche Creek, which is not impacted by dams or transbasin diversions, flowed at 195 cfs, or 70.1% of average, on April 23. Last week, the river ran at 244 cfs, or 123.9% of average.

Snowpack is steady in the Roaring Fork basin

Snowpack in the Roaring Fork basin is relatively unchanged from last week, reaching an average of 20.2 inches of snow-water equivalent per site on April 23, or 144% of median, according to NRCS.

SNOTEL sites that monitor snowfall throughout the winter measured the snowpack at Independence Pass at 112.3% of median on April 23 with a “snow water equivalent” (SWE) of 17.3 inches, up from 16.9 inches and 104.3% of normal on April 16. Last year on April 23, the SNOTEL station up the pass (located at elevation 10,600 feet) recorded an SWE of 11.7 inches.

The monitoring station at McClure Pass, located at elevation 8,770 feet, recorded a SWE of 26 inches on April 23, or 217% of median. That’s down from a SWE of 26.7 inches on April 16, but up from 191% of median. Last year, on April 23, the station measured a snowpack holding 7.3 inches of water.

On the northeast side of the Roaring Fork Basin, snowpack at Ivanhoe, which sits at an elevation of 10,400 feet, reached 18.4 inches of SWE on April 23, or 115.7% of median.

Snowpack at North Lost Trail, which sits at an elevation of 9,219 feet, has reached 24.1 inches of SWE on April 23, or 221% of median, down from 25.2 inches last week.

Snowpack at Schofield Pass reached 50.4 inches on April 23, which represents 158% of median. Schofield Pass sits at an elevation of 10,700 feet between Marble and Crested Butte.

Snow water equivalent — the metric used to track snowpack — is the amount of water contained within the snowpack, which will become our future water supply running in local rivers and streams.

Lake Powell’s water levels above target elevation for the first time in months

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 April 23, the reservoir was 22.87% full (with a total capacity based on a 1986 sedimentation survey) or 23.86% full (based on updated 2017-18 sedimentation data). That’s up from April 16, when the nation’s second-largest reservoir was at 21.86% of capacity (1986 data) or 22.81% (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 April 23, 2022, it was 23.7% full (based on 1986 data).

On April 23, Lake Powell’s elevation reached 3,525.3 feet, or 174.7 feet from full pool, up from 3,521 feet on April 16. The reservoir’s water level on April 23 was 0.3 feet above the target elevation of 3,525. That’s the first time since December that the reservoir’s elevation is above target elevation. Last year, on April 23, the reservoir reached 3,522.34 feet in elevation, or 177.66 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.

Swinging air temperatures at ASE

High air temperatures at the Aspen airport decreased from 65°F on April 12 to 40°F on April 15 before going back up to 60°F on April 17. High temperatures then dropped again to 40°F on April 19, or 13 degrees below normal. Meanwhile, low temperatures went from 37°F on April 12 to 16°F on April 15 before reaching 31°F on April 18 and then dropping to 22°F on April 19.

Worsening air quality in Aspen

The air quality in Aspen was “moderate” last week except April 20-21 when the air quality was “good” with an AQI index for ozone that reached 47 on each day. For the remainder of the week, the AQI index ranged from 55 for PM2.5 on April 19 to 84 for ozone on April 23.

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,...