Aspen Journalism is compiling a data dashboard highlighting metrics of local public interest, updated at least weekly by mid-day Tuesday.

Spring temperatures boost local streamflow

“The last few days of sunshine and unseasonably warm temperatures have brought the mixed feelings of early spring as the valley floor greens, snow melts and rivers begin to run,” the Roaring Fork Conservancy snowpack and river report of April 21 noted. “Stream flows increased substantially over the last week; flows on the Roaring Fork River have doubled and flows on the Crystal River have tripled!”

The USGS gauge on the Roaring Fork River near Aspen at Stillwater, located upstream of town, measured streamflow at 64.6 cfs on April 24, which represents 100.9% of average. That’s up from last week, when the river was flowing at 39.6 cfs. On April 24, 2021, the river ran at 29.1 cfs.

The Crystal River above Avalanche Creek, near Redstone, flowed at 363 cfs, or about 125.2% of average, on April 24. The warmer temperatures of last week increased the streamflow of the river as the Crystal jumped from 132 cfs on April 17 to 538 on April 22. The Crystal River at the CPW Fish Hatchery bridge ran at 456 cfs on Apr. 24.

Snowpack drops below average for the first time this year

Snowpack in the Roaring Fork Basin was at 89% of average, according to NOAA on April 24. It’s been below average since April 20, reaching that designation for “the first time this season,” the Roaring Fork Conservancy wrote on April 21.

SNOTEL sites that monitor snowfall throughout the winter measured the snowpack at Independence Pass at 73.7% of average on April 24, with a “snow water equivalent” (SWE) of 12.09 inches. The size of the snowpack relative to the 30-year average is down from last week’s 86.8%. Snowpack dropped from over 14 inches on April 17 to about 11.7 on April 23 due to warmer temperatures. Last year on April 24, the SNOTEL station up the pass recorded an SWE of 12.28 inches.

The monitoring station at the lower-elevation McClure Pass recorded a SWE of 7.9 inches, or 63.8% of average, on April 24. A week before, the station reported 11.8 inches of water contained in the snowpack, or 80.3% of average. Last year, on April 24, the station measured a snowpack holding 5.6 inches of water, or 45.1% of average.

On the northeast side of the Roaring Fork Basin, snowpack at Ivanhoe contains higher water levels than the 1991-2020 average, with 17.1 inches on April 24, which is 103.6% of the average of 16.5 inches. It dropped from 17.7 inches of SWE on April 17. It’s also up from last year’s 16.42 inches of SWE.

Snowpack at Schofield Pass reached 34 inches on April 24, which represents 98.3% of average. For the first time this year, Schofield Pass’ snowpack is below average. 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 elevation lost about three inches this past week

Lake Powell‘s storage reached its lowest level recorded since it began filling in the 1960s and ’70s on April 24 when the reservoir was 23.72% of full.

Last week, on April 17, the reservoir was 23.79% of full. The reservoir’s capacity has fallen since last year, when on April 24, 2021, the reservoir was 35.26% of full.

The surface elevation of Lake Powell dipped below the target elevation of 3,525 feet on March 15. The reservoir hit a record low on April 24 when its elevation dropped to 3,522.4 feet, or 177.6 feet from full pool. The reservoir has lost 3.6 inches since April 17, compared to a 6-inch decrease between March 27 and April. 3. Last year, on Apr. 24, the reservoir reached 3,563.29 feet, or 136.71 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.

Spring makes temperatures swing

Temperatures dropped dramatically around April 12-13. Maximum air temperature went from 54°F on April 11 to 27°F on April 13, which is 24 degrees below normal, before going back to above 50° on April 15, according to temperatures recorded at the Aspen/Pitkin County Airport. On April 19, maximum temperature reached 66°F. The minimum dropped from 31°F on April 11 to 9°F on April 13 before rising again to 33°F on April 15.

Air quality remains overall ‘good’ besides a peak in ozone last Wednesday

The air quality in Aspen was “good” this past week besides April 21 when the AQI index for ozone reached 61, which means that air quality was “moderate.” The AQI index for ozone ranged from 42 on April 23 and 24 to 49 on April 20 for the remainder of the week.

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,...