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

August and September 2021 wastewater volume catching up with past trends

Wastewater flow rates reported by the Aspen Consolidated Sanitation District, located near the Aspen-Pitkin County Airport, provide a benchmark that correlates with the volume of people in town at a certain point in time.

According to ACSD data, the volume of wastewater coming through the treatment plant in August and September 2021 was close to past trends. The volume of wastewater in August 2021 was about the same as in August 2020 but slightly lower than pre-pandemic seasons. The average daily flow in August 2021 of 1.426 million gallons was about 6% lower than in August 2019.

In September 2021, the volume of wastewater was at the same level as in September 2019, with an average daily flow of 1.272 million gallons but down 2% from last year.

Local streamflows back up

The USGS gauge on the Roaring Fork near Aspen at Stillwater, located upstream of town and two major diversion ditches, measured streamflow at 37.7 cfs on Oct. 3, which represents 85.7% of average. A week before, the river was flowing at 24.5 cfs. On Oct. 3, 2020, the river ran at 32.4 cfs. 

The ACES gauge, located near the Mill Street Bridge in central Aspen, measured the Roaring Fork at an average of 22.7 cfs on Oct. 3, up from 11.31 cfs on Sept. 26. The river ran at 16.07 cfs on that day last year.

The ACES gauge measures the river, which is already diminished by the diversion to the eastern slope, in an especially compromised stretch — below the Wheeler and Salvation ditches that divert water for upper valley users, and before the channel is replenished by Hunter, Castle and Maroon creeks.

Though Roaring Fork streamflow levels are back up with recent rains, the river in town remains lower than the minimum instream flow of 32 cfs established by a 1976 water rights decree. But the Stillwater stretch exceeded the threshold.

The Crystal River above Avalanche Creek, near Redstone, flowed at 97 cfs, or 86.3% of average on Oct. 3. That’s nearly double from last year, when the river ran at 53 cfs on Oct. 3, 2020. The Crystal River at the CPW Fish Hatchery bridge ran at 60.5 cfs on Oct. 3. The current streamflow remains below the minimum instream flow set at 100 cfs set by the 1979 water rights decree.

Air temperature close to 80°F last week

Air temperature measured in Aspen fluctuated between Sept. 20 and 28. The maximum temperature reached up to 79°F on Sept. 26, or 14.5°F above normal, before going down to 68°F on Sept. 28, or 4.3 degrees above normal. Meanwhile, the minimum temperature increased from 28°F on Sept. 21, or 8.4 degrees below normal, to 43°F on Sept. 28, or about 10 degrees above normal.

‘Good’ air quality in Aspen this past week

The air quality in Aspen was “good” this past week. The AQI index ranged from 30 to 41 for ozone between Sept. 27 and Oct. 3.

Lake Powell storage is below 30%

Lake Powell‘s storage kept getting lower this past week, reaching its lowest level recorded since it began filling in the 1960s and ’70s on Oct. 3, when the reservoir was 29.83% of full.

Last week, on Sept. 26, the reservoir was 30.01% of full. The reservoir’s capacity has fallen significantly since last year, when on Oct. 3, 2020, the reservoir was 46.59% of full.

The surface elevation of Lake Powell is also in decline and hit a record low on Oct. 3, 2021, when the reservoir’s elevation dropped to 3,545.3 feet, or 154.7 feet from full pool. The reservoir’s elevation has lost seven inches since Sept. 26, when the elevation was at 154 feet from full pool. Last year, on Oct. 3, the reservoir reached 3,595.55 feet or 104.45 feet from full pool.

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,...