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.

Roaring Fork River through Aspen falls far below instream flow minimum

The USGS gauge on the Roaring Fork near Aspen at Stillwater, located upstream of town and two major diversion ditches, measured streamflow at 24.5 cfs on Aug. 11, which represents 36% of average. That was down 47% from Aug. 4. On Aug. 11, 2020, the river ran at 41 cfs, or 60.3% of average. 

The ACES gauge, located near the Mill Street Bridge in central Aspen, measured the Roaring Fork at an average of 8.8 cfs on Aug. 11. The river ran at 20.88 cfs on that day last year. The ACES gauge measures the river, which is already diminished by transbasin diversions to the eastern slope from the headwaters near Independence Pass, 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 flows from Hunter, Castle and Maroon creeks.

Upper Roaring Fork streamflow rates recorded by both gauges were lower than the minimum instream flow of 32 cfs established by a 1976 water rights decree. The city this week began bypassing flows it would normally take at the Wheeler Ditch to bolster Roaring Fork levels through town by up to 3 cfs, the Aspen Daily News reported on Friday.

The Crystal River above Avalanche Creek, near Redstone, flowed at 103 cfs, or 49.8% of average on Aug. 11. That was up 30% from last year, when the river ran at 79 cfs on Aug. 11, 2020. The Crystal River at the Dow Fish Hatchery bridge ran at 61.1 cfs on Aug. 11, which is below the minimum instream flow set at 100 cfs set by the 1979 water rights decree.

First look at the 2020 Census: Tri-county population increased by 7.2%

The U.S. Census Bureau released a first batch of localized data for the 2020 Census. Colorado’s population increased by 14.8% since 2010, making it one of the fastest growing states. Locally, Pitkin, Eagle and Garfield counties gained 9,040 people over the last decade. Garfield County gained 5,296 people — a 9.39% increase from 2010. Eagle County population rose from 52,197 in 2010 to 55,731 in 2020. Pitkin County had the lowest population growth among the three counties, with a 1.22% increase from 2010. Census data doesn’t provide a full picture of our local population as part-time residents may not be included in the data.

While most mountain counties and the Front Range have seen a population increase over the past 10 years, some northwestern counties and most of the eastern and southeastern region have seen their population decline, down to a 14.3% decrease for Kit Carson County.

July 2021 wastewater flow rates higher than in 2020 but still behind pre-COVID levels

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 July 2021 was higher than July 2020 but still lower than pre-pandemic seasons. The average daily flow in July 2021 of 1.578 million gallons was 7% lower than in July 2019.

The volume of wastewater has dropped even lower than 2020 since Aug. 8, down to 1.423 million gallons on Aug. 9, which was 5% lower than on the same day in 2020 and 11% lower than on Aug. 9, 2019.

Poor air quality persists in Colorado

This past week, the air quality in Aspen was reported as “moderate” and two days (Aug. 7 and 8) that were “unhealthy for sensitive groups.” The AQI index reached 142 for PM2.5 on Aug. 7. The poor air quality was caused by smoke mostly from California fires. The Colorado Department of Public Health and Environment issued several advisories for Pitkin County over the past seven days, with the latest one being on Aug. 12 at 8 a.m. saying that smoke from out-of-state wildfires will continue to affect air quality on Thursday morning, but it will start to dissipate throughout the day.

Air temperature close to normal

On Aug. 7 maximum air temperature measured at Aspen dropped to 73°F, or about three degrees below normal. The next day, the maximum temperature rose fro 73°F to 81°F, or about 3 degrees above normal. The minimum temperature has been relatively close to normal. On Aug. 8, the minimum temperature was 46°F, which is 0.9 degrees below normal.

Lake Powell storage, surface elevation, continue record decline

Lake Powell‘s storage kept getting lower this past week, reaching its lowest level ever recorded on Aug. 11 when the reservoir was 31.8% of full, or 230,570 acre-feet lower than the previous all-time low set in 2005.

Last week, on Aug. 4, the reservoir was 32.17% of full. The reservoir’s capacity has fallen significantly since last year, when on Aug. 11, 2020, the reservoir was 49.91% of full.

The surface elevation of Lake Powell is also in decline and hit record low on Aug. 11, 2021, when the reservoir’s elevation dropped to 3,552.08 feet, or 147.92 feet from full pool. The reservoir’s elevation has lost more than one foot since Aug. 4, when the elevation was at 146.67 feet from full pool. Last year, on Aug. 11, the reservoir reached 3,604.04 feet or 95.96 feet from full pool.

If the surface elevation of the reservoir on the Utah-Arizona state line, which stores Colorado River basin water, drops below 3.525.5 feet, it would trigger a host of consequences, including impacts to Glen Canyon Dam affecting hydropower production and potential litigation between the seven states that share water under the 1922 Colorado River Compact. The federal Bureau of Reclamation has begun releasing more water from reservoirs upstream in the basin to avoid this scenario.

Laurine Lassalle

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,...