Data dashboard: Soil moisture catching up after a drier-than-usual start



Aspen Journalism compiles a data dashboard highlighting local public policy measures, updated at least every Tuesday. Check back for updates as we add more features.

Soil 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 Glenwood Springs station measures soil moisture at a depth of 2 inches and 8 inches. While the 8-inch depth measurement captures changes in soil moisture over the seasons, drying out episodes, and moderate to heavy rains, the 2-inch depth data also reflects air temperature.

The ground at Glenwood Springs station was drier than the 2016-2020 average at the start of the year for both depths. On January 1, 2021, the Glenwood Springs station recorded an average of 0.09 m3 / m3 of water for the day at 2 inches depth, compared to 0.17 m3 / m3 on average between 2016 and 2020. That same day , the station measured an average of 0.15 m3 / m3 of water at a depth of 8 inches, lower than the 2016-2020 average of 0.21 m3 / m3.

The Sky Mountain Park Park monitoring station recorded a similar pattern, according to data provided by AGCI. As has been observed throughout the Colorado River Basin, these dry soils resulted in decreased runoff and flow in the spring.

“It is also interesting to note that these were dry soils compared to the 2016-2020 average, which was himself in a period of record drought, compared to previous decades in the Roaring Fork Valley, ”wrote Elise Osenga, community science manager at AGCI, in an email.

Dry soils early in the season can increase fire risk and plant stress, Osenga wrote.

Rainstorms that occurred this summer brought a brief increase in moisture to the soils of 2 inches, but the soils tended to drain and dry out quickly over the following days, according to AGCI and Osenga.

Dry soils are common in Glenwood Springs at a depth of 8 inches during the summer, but this year the soils dried out early and remained dry until August, according to AGCI and Osenga. Conditions were particularly dry in mid-April and May, but more closely followed the five-year average since early August.

On September 19, 2021, the soil contained 0.07 m3 / m3 of water at a depth of 2 inches at the Glenwood Springs station, below the 2016-2020 average of 0.09 m3 / m3. At 8 inches deep, the Glenwood Springs station recorded 0.13 m3 / m3 of water, compared to 0.14 on average between 2016 and 2020.

Crystal and Roaring Fork rivers continue to flow below minimum reserve flow

The USGS gauge on the Roaring Fork near Aspen in Stillwater, located upstream of town and two main bypass ditches, measured flow at 26.4 cfs on September 19, which is 55% of the average. Last week the river flowed at 29.6 cfs. On September 19, 2020, the river flowed 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 September 19, down from 12.03 cfs on September 12. The river was flowing at 25.66 cfs that day last year.

The ACES gauge measures the river, which is already diminished by the diversion to the eastern slope, in a particularly compromised stretch – below the Wheeler and Salvation ditches which divert water for users in the upper valley, and before the canal is replenished by Hunter, Castle and The Brown Coves.

Roaring Fork flow levels are below the minimum reserve flow of 32 cfs established by a 1976 Water Rights Order. They dropped drastically on September 16 for about 36 hours, dropping to less than 2 cfs at Mill Street in the early morning of September 17, before rebounding to 16.68 cfs on September 18. The USGS Stillwater’s gauge dropped the fork to 17.7 cfs on September 16, but climbs back to 34 cfs on September 18.

A representative from Twin Lakes Reservoir and Canal Co., which manages the Independence Pass Basin Diversion System, confirmed the drop was linked to an annual inspection of the Grizzly Reservoir Dam facilities along Lincoln Creek. This required shutting off the water flowing from the dam on September 15. Operations returned to normal the next day. At this time of year, as stream flow levels approach their low point, most of the water in the upper Roaring Fork is tied to whatever comes out of Grizzly Reservoir. On September 22, Lincoln Creek below the reservoir was operating at 16.5 cfs, according to a USGS gauge.

The Crystal River above Avalanche Creek near Redstone was flowing at 71 cfs, or 60.9% of the average on September 19. This was 13% more than last year, when the river flowed at 63 cfs on September 19, 2020. The river at the Dow Fish Hatchery Bridge was flowing at 14.9 cfs on September 19. The current flow remains below the minimum reserved flow set at 100 cfm set by the 1979 water rights decree.

Air temperature remains above normal

Over the past week, the air temperature measured in Aspen dropped slightly but remained above normal, 81 ° F on September 15, or 12.3 ° F above normal. The minimum temperature was closer to normal, up to 48 ° F on September 13 or 8.8 degrees above normal.

Improving air quality in Aspen

Air quality in Aspen improved over the past week, with just two days when the air was reported as “moderate”. The AQI index reached 61 for ozone on September 15 and 54 on September 16. In addition to these two days, the air quality was “good” with an AQI ozone rating dropping to 41 on September 13th.

Lake Powell continues to sink

Lake Powell’s storage continued to decline over the past week, reaching its lowest level recorded since it began to fill in the 1960s and 1970s on September 19, when the reservoir was 30.33% full.

Last week, September 12, the tank was 30.67% full. The capacity of the tank has decreased significantly since last year, when on September 19, 2020, the tank was 47.28% full.

The surface elevation of Lake Powell is also declining, and reached an all-time high on September 19, 2021, when the reservoir’s elevation fell to 3,547.1 feet, or 152.9 feet from the full pool. The reservoir’s elevation has lost a foot since September 12, when the elevation was 151.8 feet from the full pool. Last year on September 19, the reservoir reached 3,597.35 feet or 102.65 feet from the full pool.



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