Tooele County ended the 2022 water year in extreme drought despite experiencing one of the wettests Augusts in the past 128 years.
Precipitation recorded in mountain sites around Tooele Valley from Oct. 1, 2021 to Sept. 30, 2022 averaged 90% of the median value for the 30-year period from 1991-2020, according to a report from the U.S. National Conservation Resource Service.
Nevertheless, the U.S Drought Monitor listed Tooele County, as well as most of Utah, as in an extreme drought as of Sept. 29, 2022.
The Drought Monitor uses several indexes that measure soil moisture, streamflow data, temperature records and precipitation records to determine long-range drought conditions. Extreme drought conditions are described by the Drought Monitor as “experiencing major drop and pasture losses and widespread water shortages or restrictions.”
The 2021-2022 water year started out hopeful with above median precipitation from October 2021 through February 2022, but then dry weather persisted to record lower than median precipitation for the remainder of the year.
August 2022 however, was the 16th wettest August over the past 128 years, according to drought.gov.
In August 2022, 4 inches of precipitation fell at the NRCS Rocky Basin-Settlement Canyon recording site compared to a normal 30-year median of 1 inch.
Across the valley, at the NRCS Mining Fork recording site in South Willow Canyon, 3.4 inches of precipitation was recorded in August 2022 compared to a normal of 1.3 inches.
Annual precipitation in Tooele over the 30-year period from 1991-2022 ranged from 26.7 inches in 1998 to 7.7 inches in 2020, according to the National Oceanic and Atmospheric Administration. Prior to 2020’s low record, the driest year in Tooele was 1992 with an annual precipitation of 12.8 inches, according to NOAA.
Settlement Canyon and Grantsville reservoirs, the two largest reservoirs in Tooele County, were quite disparate in their capacity at the end of the 2022 water year.
As the new 2022-2023 water year started, the Grantsville Reservoir sat at above normal level with 33.2% of capacity compared to a median value of 24.2% for the beginning of October.
In contrast, the Settlement Canyon Reservoir held 17.7% of its capacity as the 2023 water year started compared to a normal median value 30.0%.
Meteorologists and water-watchers also use soil moisture content as an indicator to monitor not only drought and flood forecasting, but also to forecast agriculture production and for forest fire predictions.
A high soil moisture content in the hills around a water basin at the start of the snow season means more spring runoff will make its way to streams, reservoirs, and groundwater than if dry soil trapped the runoff in its pores.
In a September 2022 Drought Update, amidst a record breaking heat wave that saw 34 days of 100 degree plus temperatures in Salt Lake County, Candice Hasenyager, director of the state Division of Water Resources said: “Scorching temperatures statewide have taken a toll on our soil moisture this past week. If this trend continues, it means less water will make its way to our streams and reservoirs during next year’s spring runoff.”
Three of the four NRCS sites in Tooele Valley started the 2022-2023 water year with soil moisture content above normal.
The Vernon Creek, Rocky Mountain-Settlement Canyon, and Dry Fork sites were at 178%, 138% and 122% of their normal value respectively as the 2023 water year started.
The Mining Fork site was at 90% of normal, according to the NRCS.
The U.S. Drought Monitor’s monthly Drought Outlook report indicates that drought conditions in Utah are unlikely to change through the end of October.
The NRCS uses remote battery powered sites across western mountains that automatically measure and transmit information about snow depth, water content, rainfall, and air temperature. The NRCS uses four sites to gather data in Tooele Valley — the Mining Fork site in South Willow Fork, the Rocky Basin-Settlement Canyon site, the Vernon Creek site and the Dry Fork site on top of the Oquirrh Mountains.
The U.S. Drought Monitor is a team effort, produced jointly by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the National Oceanic and Atmospheric Administration, and the U.S. Department of Agriculture.