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.
Soils moisture improves after drying early this year
The Aspen Global Change Institute maintains a network of monitoring stations throughout the Roaring Fork watershed that track soil-moisture levels. The station in Glenwood Springs measures soil moisture at a 2-inch and an 8-inch depth. While the 8-in depth measurement captures changes in soil moisture across seasons, drying events and moderate or heavy rains, the 2-inch depth data also reflects air temperature.
The soil at the Glenwood Springs station was drier than the 2016-2020 average at the start of the year for both depths. On Jan. 1, 2021, the Glenwood Springs station recorded an average of 0.09 m3/m3 of water for the day at 2-inch depth, compared to 0.17 m3/m3 on average between 2016 and 2020. On that same day, the station measured an average of 0.15 m3/m3 of water at 8-inch depth, lower than the 2016-2020 average of 0.21 m3/m3.
The monitoring station at Sky Mountain Park Park recorded a similar pattern, according to data provided by AGCI. As has been observed throughout the Colorado River basin, these dry soils led to decreased runoff and streamflow in the spring.
“It is also worth noting that these were dry soils compared to the 2016-2020 average, which was itself in a drought period of record, compared to previous decades in the Roaring Fork Valley,” Elise Osenga, community science manager at AGCI, wrote in an email.
Dry soils early in the season can increase fire risk and plant stress, Osenga wrote.
Rain storms that occurred this summer brought a short boost in moisture to 2-inch soils, but soils tended to drain and dry quickly in the following days, according to AGCI and Osenga.
Dry soils are common in Glenwood Springs at 8-inch depth over the summer, but this year soils dried early and remained dry into August, according to AGCI and Osenga. Conditions were particularly dry in mid-April and May, but have been following the five-year average more closely since early August.
On Sept. 19, 2021, the soil contained 0.07 m3/m3 of water at 2-inch depth at the Glenwood Springs station, lower than the 2016-2020 average of 0.09 m3/m3. At 8-inch depth, the Glenwood Springs station recorded 0.13 m3/m3 of water, compared to 0.14 on average between 2016 and 2020.
The Crystal and Roaring Fork rivers continue to run lower than their minimum instream flow
The USGS gauge on the Roaring Fork near Aspen at Stillwater, located upstream of town and two major diversion ditches, measured streamflow at 26.4 cfs on Sept. 19, which represents 55% of average. Last week, the river was flowing at 29.6 cfs. On Sept. 19, 2020, the river ran at 43.1 cfs.
The ACES gauge, located near the Mill Street Bridge in central Aspen, measured the Roaring Fork at an average of 11.8 cfs on Sept. 19, down from 12.03 cfs on Sept. 12. The river ran at 25.66 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.
Roaring Fork streamflow levels are lower than the minimum instream flow of 32 cfs established by a 1976 water rights decree. They fell drastically on Sept. 16 for about a 36-hour period, dropping to below 2 cfs at Mill Street early on the morning of Sept. 17, before rebounding to 16.68 cfs by Sept. 18. The USGS Stillwater gauge had the Fork falling to 17.7 cfs on Sept. 16, but spiking back up to 34 cfs on Sept. 18.
A representative of the Twin Lakes Reservoir and Canal Co., which manages the Independence Pass transbasin diversion system, confirmed that the drop was related to an annual inspection of dam facilities at Grizzly Reservoir, along Lincoln Creek. This necessitated a shut off of water flowing out of the dam on Sept. 15. Operations returned to normal the following day. At this time of the year as streamflow levels near their low point, most of the water in the upper Roaring Fork is tied to whatever is coming out of Grizzly Reservoir. On Sept. 22, Lincoln Creek below the reservoir was running at 16.5 cfs, according to a USGS gauge.
The Crystal River above Avalanche Creek, near Redstone, flowed at 71 cfs, or 60.9% of average on Sept. 19. That was 13% up from last year, when the river ran at 63 cfs on Sept. 19, 2020. The Crystal River at the Dow Fish Hatchery bridge ran at 14.9 cfs on Sept. 19. The current streamflow remains below the minimum instream flow set at 100 cfs set by the 1979 water rights decree.
Air temperature remains higher than normal
Over the past week, air temperature measured in Aspen went slightly down but remained higher than normal, 81°F on Sept. 15, or 12.3°F above normal. The minimum temperature was closer to normal, up to 48°F on Sept. 13 or 8.8 degrees above normal.
Air quality improving in Aspen
The air quality in Aspen improved this past week, with only two days during which the air was reported as “moderate.” The AQI index reached 61 for ozone on Sept. 15 and 54 on Sept. 16. Besides these two days, the air quality was “good” with an AQI index for ozone down to 41 on Sept. 13.
Lake Powell keeps getting lower
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 Sept. 19, when the reservoir was 30.33% of full.
Last week, on Sept. 12, the reservoir was 30.67% of full. The reservoir’s capacity has fallen significantly since last year, when on Sept. 19, 2020, the reservoir was 47.28% of full.
The surface elevation of Lake Powell is also in decline and hit a record low on Sept. 19, 2021, when the reservoir’s elevation dropped to 3,547.1 feet, or 152.9 feet from full pool. The reservoir’s elevation has lost one foot since Sept. 12, when the elevation was at 151.8 feet from full pool. Last year, on Sept. 19, the reservoir reached 3,597.35 feet or 102.65 feet from full pool.
