The Settlement Canyon Irrigation Company reported at about 7:50 a.m. on Friday, June 2, that the Settlement Canyon Reservoir had reached capacity and was starting to run over the spillway into the dry creek bed below.
“It’s over the spillway! As it gets into the creekbed below the dam, the ground seems to be absorbing a lot of the water along the way,” read the post on the irrigation company’s Facebook page.
The Settlement Canyon Reservoir holds 1.0 kilo-acre-feet of water when it is at capacity, after that the water starts to run over the spillway. The Utah Division of Water Resources reported that as of the end of June 1, 2023 the Settlement Canyon Reservoir was at 97.3% capacity. The 30-year-median for the same date was 80% and the 2022 level for the same date was 40%.
The Settlement Reservoir made a steep climb in May 2023. It rose from 38% capacity on May 1, 2023 to over 97% on June 1, 2023.
There may be more water to come. The National Resource Conservation Service reported that as of June 2, 2023 there was 10.1 inches of snow water equivalent at the monitoring site at Rocky Basin-Settlement Canyon.
The 30-year median for snow water equivalent at the Rocky Basin-Settlement Canyon monitoring site on June 2 is zero inches. In 2019, the last year that the Settlement Canyon Reservoir overflowed, the NRCS reported 24.8 inches of snow water equivalent at the Rocky Basin-Settlement Canyon site on June 2.
Although the reservoir is spilling over, that doesn’t mean there will be flooding, according to Tooele City and County officials.
When Settlement Canyon Reservoir reaches capacity and overflows, the water runs into a pipe that carries the water under state Route 36 and 700 South and eventually towards the Tooele Army Depot.
Usually flood waters are contained under the road, but if it does overflow, water may run down the street [700 South], according to Bucky Whitehouse, Tooele County Emergency Management director.
When measuring large volumes of water, the unit of an acre-foot of water is used, which is enough water to cover one acre of land at a depth of one foot. Larger volumes of water are reported as KAF — kilo-acre-feet — which is equal to 1,000 acre-feet or 325,851,429 gallons.
Using the Olympic Sized Swimming Pool unit of volume, a KAF would fill 493.7 OSSP, with one standard Olympic size swimming pool holding approximately 660,000 gallons.
The Settlement Canyon Reservoir, with a capacity of 1.0 KAF of water, holds enough water to fill 493.7 Olympic size swimming pools or approximately 325,851,429 gallons.
Grantsville Reservoir is also full, according to the Division of Water Resources, which reported on June 1, 2023, that the reservoir reached 100.1% of its capacity. The 30-year-median for the Grantsville Reservoir on the same date is 90.1% and the 2022 level for the same date was 71.5%.
The Grantsville Reservoir holds 3.3 KAF of water when it is at capacity
The National Resource Conservation Service reported that as of June 2, 2023 there was no snow left at the monitoring site at the Mining Fork monitoring site located in South Willow Fork.
The water that was detoured through Grantsville City towards the Clark Historic Farm in early May 2023 was from Magpie and Baker Canyons that are north of the Grantsville Reservoir. The runoff from these canyons do not flow into the Grantsville reservoir.
In May 2017, the Transcript Bulletin wrote about the impending overflowing of the Grantsville Reservoir. The watermaster for the Grantsville Irrigation Company at the time reported that when the reservoir overflows, the water can be turned out through a ditch onto the Tooele Army Depot into a pond.