San Pitch water supplies remain critically low despite wet July

SALT LAKE CITY—Despite a wet July that brought more than twice the normal rainfall to the San Pitch watershed, water supplies across the basin remain critically low, according to the Utah Water Availability Update released Aug. 1 by the USDA Natural Resources Conservation Service.

The report shows the San Pitch basin received 2.5 inches of precipitation during July, or 225% of normal, providing a welcome boost to soil moisture. However, water-year precipitation from Oct. 1 through July 31 remained at just 81% of the 1991-2020 median, reflecting the lingering effects of a poor winter snowpack.

Mountain soil moisture also improved significantly following the monsoon storms, climbing to 59% saturation compared with 46% at the same time last year.

Even with those improvements, reservoir conditions in the basin continued to deteriorate.

The report shows reservoirs in the San Pitch watershed were just 4% full as of Aug. 1, down sharply from 22% at the same point last year. Basinwide storage totaled approximately 900 acre-feet out of a 20,000 acre-foot capacity. Gunnison Reservoir, the primary storage facility included in the report, was listed at 4% capacity.

The state’s Water Availability Index, which combines reservoir storage and streamflows to estimate current surface water supplies, ranked the San Pitch basin in the 13th percentile statewide.

That means current water availability exceeds about 13% of historical years but is below levels for 87% of the years. That places the basin among Utah’s driest watersheds despite recent rainfall. The report identified 2002 and 2016 as years with similar hydrologic conditions.

The statewide report noted that while July’s monsoonal moisture improved mountain soil moisture, reduced evaporation and lowered fire risk in many areas, summer rainfall does little to replenish reservoirs because Utah’s water supply is primarily driven by spring snowmelt.

The monthly Utah Water Availability Update is produced by the Utah Snow Survey, a service of USDA Natural Resources Conservation Service. The survey tracks precipitation, soil moisture, streamflow and reservoir conditions throughout the state.