Aspen Journalism is compiling a data dashboard highlighting metrics of local public interest, updated at least every Friday. Check back for updates as we add more features.

Traffic in town dropped in 2020 but is now catching up

When the ski lifts shut down in mid-March 2020, the city of Aspen recorded a significant drop in traffic at the intersection of Highway 82 and Cemetery Lane, located at the entrance of town, from an average of 15,501 per day in March 2020 to 8,462 in April 2020. But this year, the daily average for the months of March through June reported by the city is getting back to 2019 levels, up to 23,510 per day on average for June 2021 (compared to 23,259 for June 2019).

Fires in the Northwest affected local air quality this week

Fires in the northwestern region of the United States aided by winds brought smoke to Colorado and the Roaring Fork Valley, leading the Colorado Department of Health and Environment to issue an air quality advisory warning on July 12. The smoke affected the local air quality index, which reached a 24-hour average for PM 2.5 of 93 on July 12, and a maximum reading of 104 in the afternoon that day, reaching into the range considered unhealthy for sensitive groups. A total of four days this week reported “moderate” air quality, which means the the daily average index reading was between 51 and 100.

Air temperature getting back to normal

Air temperature reached up to 92°F on July 9, which was nearly 12 degrees above normal. But ever since, maximum and minimum temperatures are getting back closer to normal. On July 11, the maximum temperature was 83°F, about three degrees above normal. The minimum temperate was down to 46°F, less than one degree below normal.

Water levels remain low for the season

The stream gauges recorded a spike in flow rates for the Roaring Fork River, the Crystal River and the Twin Lakes Tunnel between July 13 and 14 — but remain low compared to the average.

The Roaring Fork River at Glenwood Springs ran at 730 cfs on July 14, which represents 33.18% of average — up from 662 cfs on July 13. Last year, the river flowed at 799 cfs on July 14, which was 36.32% of average.

Near the Colorado-Utah state line, the USGS gauge measured the Colorado River flowing at 2,240 cfs, or 29.79% of average, which is close to last year’s rate. On July 14, 2020, the river ran at 2,320 cfs — or 30.85% of average.

According to the Roaring Fork River Conservancy’s weekly report, a senior water rights holder on the Colorado River placed a call on the river for their water, which increased releases from Ruedi Reservoir and cooled the Fryingpan and lower Roaring Fork.

The gauge operated by the Aspen Center for Environmental Studies near the Mill Street bridge is the only gauge indicating Roaring Fork steam flow as the river runs through central Aspen. This is an important reading, distinct from the U.S. Geological Survey gauge upstream at Stillwater, since the ACES gauge measures the river below the Salvation and Wheeler ditch diversions. It therefore shows the Roaring Fork at its most endangered, reduced by both transbasin diversions to the Front Range from the headwaters near Independence Pass and by local water users — and before the channel is replenished by flows from Hunter, Castle and Maroon creeks.

The ACES gauge shows that on July 14, the river was flowing at about 50 cfs on average, compared to approximately 726 cfs on the same day in 2019. The river was also particularly low last year, when the Roaring Fork River ran at about 56 cfs on July 14, 2020. 

Lake Powell‘s storage kept getting lower this past week. On July 14, the reservoir was 33.3% of full, compared to 33.8% full on July 7. The reservoir’s capacity has fallen significantly since last year, when on July 14, 2020, the reservoir was 51.88% of full.

The surface elevation of Lake Powell is also in decline. On July 14, 2021, the reservoir’s elevation was at 3,557.3 feet or 142.8 feet from full pool. It was at 141.12ft from full pool on July 7. Last year, on July 14, the reservoir reached 3,608.9 feet or 91.1 feet from full pool.

If the surface elevation of the reservoir on the Utah-Arizona state line, which stores Colorado River water, drops below 3.525.5 feet, it would trigger a host of consequences, including impacts to the operation of Glen Canyon Dam affecting hydropower production, releases from upstream reservoirs to prop up Lake Powell, and potential litigation between the seven states that share water under the 1922 Colorado River Compact.

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,...