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

Roaring Fork basin sites all exceed their snowpack seasonal peaks

Note: Local snowpack readings and chart are now using the percent of median instead of percent of average.

Snowpack in the Roaring Fork basin reached an average of 23 inches of snow-water equivalent per site on April 9, or 145% of median, according to NRCS. All Roaring Fork basin sites have now exceeded their median seasonal peaks.

SNOTEL sites that monitor snowfall throughout the winter measured the snowpack at Independence Pass at 107.3% of median on April 9 with a “snow water equivalent” (SWE) of 17.6 inches, up from 17.2 inches on April 2 and exceeding its median seasonal peak of 17.4 inches. Last year on April 9, the SNOTEL station up the pass (located at elevation 10,600 feet) recorded an SWE of 14.1 inches.

The monitoring station at McClure Pass located at elevation 8,770 feet recorded a SWE of 29.2 inches on April 9, or 196% of median. That’s up from a SWE of 28.8 inches on April 2. Last year, on April 9, the station measured a snowpack holding 12 inches of water. It’s the second highest snowpack recorded at this site for that day between 1991 and 2020, right behind 29.5 inches on April 9, 1993. The record high for any day at site is 30.9 inches.

On the northeast side of the Roaring Fork Basin, snowpack at Ivanhoe, which sits at an elevation of 10,400 feet, reached 17.9 inches of SWE on April 9, or 119.3% of median. Snowpack at this site is now exceeding its median seasonal peak of 17.2 inches.

Snowpack at North Lost Trail, which sits at an elevation of 9,219 feet, has reached 29.4 inches of SWE on April 9, or 181% of median. It’s the second highest recorded for that day between 1991 and 2020, beating April 9, 2008’s 29.2 inches. The highest amount of SWE recorded at this station for any day is 30.8 inches.

Snowpack at Schofield Pass, which boasts the largest SWE accumulation of any monitoring site in the basin, reached 49.2 inches on April 9, which represents 157.7% of median. Schofield Pass sits at an elevation of 10,700 feet between Marble and Crested Butte.

Snowpack at that site has been exceeding its median seasonal peak of 35.1 inches since March 11 (seasonal peaks typically come around mid April). McClure Pass, which as we reported in March is saw especially high snowpack readings this winter like other mid elevations stations, topped its median seasonal peak of 16.6 inches on Feb. 14 this year.

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.

Local streams are still flowing well below average

As most of the spring runoff has yet to start melting, streamflows in the Roaring Fork basin are below average but on par with last year’s flows.

The USGS sensor on the Roaring Fork river below Maroon Creek hasn’t recorded any streamflow data since mid-December due to ice.

At Emma, below the confluence with the dam-controlled Fryingpan, the April 9 streamflow of 244 cfs represented about 67% of average. That’s up from 190 cfs, and 61.3% of average, on April 2.

At Stillwater, located upstream of Aspen, the Fork on April 9 ran at 21.3 cfs or 54.6% of average, up from 14.6 cfs and 45.6% of average, on April 2.

The transbasin diversion that sends Roaring Fork basin headwaters to Front Range cities was flowing at 7.9 cfs on April 9.

Meanwhile, the Crystal River above Avalanche Creek, which is not impacted by dams or transbasin diversions, flowed at 91 cfs, or 63.2% of average, on April 9. Last week, the river ran at 56 cfs, or 52.1% of average.

Lake Powell refilling on pause

Lake Powell‘s water levels began their seasonal rise in mid-March as rising temperatures initiated snowmelt, after the reservoir dropped to its lowest level on record since filling, but that refilling was stalled by cold temperatures. On April 9, the reservoir was 21.73% full (with a total capacity based on a 1986 sedimentation survey) or 22.67% full (based on updated 2017-18 sedimentation data). That’s down slightly from April 2, when the nation’s second-largest reservoir was at 22.06% of capacity (1986 data) or 23.01% (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 9, 2022, it was 23.86% full (based on 1986 data).

On April 10, Lake Powell’s elevation reached 3,520.4 feet, or 179.6 feet from full pool, down from 3,521.9 feet on April 2. The reservoir’s water level on April 9 was 4.6 feet below the target elevation of 3,525. Last year, on April 9, the reservoir reached 3,522.9 feet in elevation, or 177.01 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 keep swinging

High air temperatures at the Aspen airport dropped from 51°F on March 29 to 33°F on March 31 before going back up to 50°F on April 3, or about two degrees above normal. Meanwhile, low temperatures decreased from 19°F on March 29 to 15°F on April 1 before reaching 33°F on April 3, or about eight degrees above normal.

Two days of “moderate” air quality reported last week in Aspen

The air quality in Aspen was “good” last week except April 6 and 9 when the air quality was “moderate” with an AQI index for ozone that reached 54 and 51, respectively. For the remainder of the week, the AQI index ranged from 44 on April 5 to 49 on April 8.

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,...