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

Snowpack is on the decline

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

Snowpack in the Roaring Fork basin is now trending down with the arrival warmer temperatures last week. Snowpack in the basin reached an average of 20.4 inches of snow-water equivalent per site on April 16, or 133% of median, according to NRCS.

SNOTEL sites that monitor snowfall throughout the winter measured the snowpack at Independence Pass at 104.3% of median on April 16 with a “snow water equivalent” (SWE) of 16.9 inches, down from 17.6 inches and 107% of normal on April 9. Last year on April 16, the SNOTEL station up the pass (located at elevation 10,600 feet) recorded an SWE of 14.5 inches.

The monitoring station at McClure Pass located at elevation 8,770 feet recorded a SWE of 26.7 inches on April 16, or 191% of median. That’s down from a SWE of 29.2 inches on April 9, which was 196% of median. Last year, on April 16, the station measured a snowpack holding 12.2 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 inches of SWE on April 16, or 111.8% of median.

Snowpack at North Lost Trail, which sits at an elevation of 9,219 feet, has reached 25.2 inches of SWE on April 16, or 176% of median, down from 29.4 inches last week.

Snowpack at Schofield Pass, which boasts the largest SWE accumulation of any monitoring site in the basin, reached 45.1 inches on April 16, which represents 134.2% 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.

Spring runoff takes off with above average streamflows

Streamflows in the Roaring Fork basin are now above average with the runoff beginning to kick in.

The USGS sensor on the Roaring Fork river below Maroon Creek resumed recording streamflow data after ice affected the sensor this winter. The Fork ran at 164 cfs on April 16, or 139% of average, after peaking at 243 cfs on April 14.

At Emma, below the confluence with the dam-controlled Fryingpan, the April 16 streamflow of 412 cfs represented about 101.7% of average. That’s up from 244 cfs, and 67% of average, on April 9.

At Stillwater, located upstream of Aspen, the Fork on April 16 ran at 55.2 cfs or 117.4% of average, after spiking up to 78.5 cfs on April 13 due to spring runoff. That’s up from 21.3 cfs and 54.6% of average, on April 9.

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

Meanwhile, the Crystal River above Avalanche Creek, which is not impacted by dams or transbasin diversions, flowed at 244 cfs, or 123.9% of average, on April 16. Last week, the river ran at 91 cfs, or 63.2% of average.

Lake Powell’s water levels slightly up from last week

Lake Powell‘s water levels began their seasonal rise in mid-March as warming temperatures initiated snowmelt, after the reservoir dropped to its lowest level on record since filling in winter. On April 16, the reservoir was 21.86% full (with a total capacity based on a 1986 sedimentation survey) or 22.81% full (based on updated 2017-18 sedimentation data). That’s up slightly from April 9, when the nation’s second-largest reservoir was at 21.73% of capacity (1986 data) or 22.67% (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 16, 2022, it was 23.79% full (based on 1986 data).

On April 16, Lake Powell’s elevation reached 3,521 feet, or 179 feet from full pool, up from 3,520.4 feet on April 9. The reservoir’s water level on April 10 was 4 feet below the target elevation of 3,525. Last year, on April 16, the reservoir reached 3,522.69 feet in elevation, or 177.31 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.

ASE temps hit 14°F above normal

High air temperatures at the Aspen airport increased from 50°F on April 3 to 65°F on April 12, or 14 degrees above normal. Meanwhile, low temperatures went from 33°F on April 3 to 37°F on April 12, or about 10 degrees above normal.

‘Moderate’ air quality in Aspen last week

The air quality in Aspen was “moderate” last week except April 14 and 15 when the air quality was “good” with an AQI index for ozone that reached 49 and 50, respectively. For the remainder of the week, the AQI index ranged from 51 on April 10 to 61 on April 13.

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,...