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

Roaring Fork and Crystal rivers’ streamflow well above average

The USGS gauge on the Roaring Fork River near Aspen at Stillwater, located upstream of town, measured streamflow at 247 cfs on May 15, which is 148.8% of average. That’s up from last week, when the riveu,r was flowing at 144 cfs. On May 15, 2021, the river ran at 92 cfs.

The ACES gauge, located near the Mill Street Bridge in central Aspen, measured the Roaring Fork River flowing at 223.66 on May 15. That’s lower than the Stillwater reading because the Wheeler and Salvation diversion ditches are again operating for the season. It’s also up from 128.6 cfs last week.

The Crystal River above Avalanche Creek, near Redstone, flowed at 1,340 cfs, or about 195.9% of average, on May 15. The warmer temperatures of the past week increased the streamflow of the river as the Crystal jumped from 1,060 cfs on May 13. The Crystal River at the CPW Fish Hatchery bridge ran at 1,650 cfs on May 15, up from 1,300 cfs on May 8.

Roaring Fork basin snowpack drops to less than 50% of average

Snowpack in the Roaring Fork Basin was at 48% of average, according to NOAA on May 15. 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 4.1% of average on May 15, with a “snow water equivalent” (SWE) of 0.39 inches. The size of the snowpack relative to the 30-year average is down from last week’s 52.6%. Snowpack dropped from over six inches on May 8 to about less than one inch on May 15 due to warmer temperatures. Last year on May 15, the SNOTEL station up the pass recorded an SWE of 4.09 inches.

The monitoring station at the lower-elevation McClure Pass recorded a SWE of 0.2 inches, or 4.6% of average, on May 15. A week before, the station reported 0.31 inches of water contained in the snowpack, or 4.6% of average. Last year, on May 15, the station measured a snowpack holding 0 inches of water.

On the northeast side of the Roaring Fork Basin, snowpack at Ivanhoe now contains lower water levels than the 1991-2020 average, with 8.11 inches on May 15, which is 68.2% of the average of 11.9 inches. It dropped from 16.81 inches of SWE on May 6. It’s down from last year’s 12.2 inches of SWE.

Snowpack at Schofield Pass reached 20.59 inches on May 15, which represents 72.2% of average. Schofield Pass’ snowpack has been below average for about three weeks. 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 level is slowly increasing

Lake Powell‘s storage remains at one of its lowest levels recorded since it began filling in the 1960s. However, the amount of water stored in the reservoir increased over the past three weeks, as the annual runoff boosted river flows.

On May 11, the reservoir was 23.95% full. Last week, on May 8, it was 23.88% full. The reservoir’s capacity has fallen since last year, when on May 11, 2021, the reservoir was 34.55% of full.

The surface elevation of Lake Powell dipped below the target elevation of 3,525 feet on March 15, but it gained 3.6 inches between May 8 and May 11. On May 11, Lake Powell’s elevation reached 3,523.4 feet, or 176.7 feet from full pool, up from 3,523.1 feet on May 8. Last year, on May 11, the reservoir reached 3,561.05 feet, or 138.95 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 temperature on the rise

Temperatures have been on the rise over the past two weeks. Maximum air temperature reached up to 74°F on May 11, which is about 14 degrees above normal, according to temperatures recorded at the Aspen/Pitkin County Airport. The minimum was closer to normal. It ranged from 23°F on April 30, which is about seven degrees below normal, to 45°F on May 7, about six degrees above normal.

Air quality was ‘good’ in Aspen besides two days with ‘moderate’ air quality

The air quality in Aspen was “good” this past week besides May 9 and May 12 when air quality was moderate and the AQI index for ozone reached 61 and 74, respectively. This decline in air quality was probably caused by wildfires burning in New Mexico and Arizona and the prescribed burned across Colorado. Jannette Whitcomb, Aspen senior environmental health specialist, wrote in an email that it is commonplace to see moderate AQI for ozone in Aspen in the spring.

For the remainder of the week, the AQI index for ozone ranged from 42 on May 15 to 50 on May 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,...