IDAHO FALLS, Idaho (KIFI) - The Natural Resources Conservation Service in Idaho has released the June Water Supply Outlook Report for the 2022 Water Year.
A cold and wet spring has improved water supply across Idaho by increasing natural streamflow, delaying and/or diminishing irrigation deliveries and postponing mountain snowpack melting Erin Whorton, Hydrologist-Water Supply Specialist for NRCS Snow Survey says "that means that water is going to be available coming into the reservoirs and available later in the summer."
Another month of wet and cold weather brought water year total precipitation to near or above normal across Idaho. During the annual Bureau of Reclamation Upper Snake River ‘windshield’ tour on May 20, the snowpack appeared to be greater this year than recent analogous years of 2021, 2013, 2003 and 2002.
May precipitation was near to well above normal across most of Idaho (100% to 217%). Boise Basin was the wettest at 217% of normal precipitation. Many basins have reached near normal to slightly above normal total water year precipitation levels. The biggest gains since April 1 occurred in the West Central, Wood, Lost and Upper Snake basins with 11% to 16% increases compared to the thirty-year normal. Total water year precipitation across Idaho basins ranged from 91% (Henrys Fork-Teton) to 109% (Birch-Medicine Lodge-Beaver-Camas).
Water supply conditions have improved since the April 1 assessment. The wet spring conditions have increased natural flow in the rivers, increased runoff into reservoirs, have improved soil moisture conditions and in some places, have delayed or decreased irrigation deliveries.
Reservoir storage is still below normal across Idaho. Total reservoir storage in the Upper Snake system above American Falls Dam is 58% full and well below normal at 76% of average storage on June 1. There is ~817.3 thousand acre-feet less water currently in the system compared to this time last year.
Much of Idaho is still in drought and water supply will continue to be limited this irrigation season.
“The cold, wet spring continued to slow down how quickly the snowpack is melting,” said Whorton. “All SNOTEL sites not previously melted out recorded a decrease in snow-water equivalent during May.”
The one month outlook from NOAA’s Climate Prediction Center (CPC) suggest June will be colder and wetter than normal in northern Idaho. South of the Salmon Basin and in the Upper Snake, the models indicate equal chances for both temperature and precipitation conditions to be above, normal or below normal. However, the mid-range forecasts indicate warm and dry conditions during the next few weeks in these basins. These forecasts show above-normal precipitation in northern Idaho.
The CPC three-month outlook for June-July-August predicts warmer and drier conditions than normal this summer across Idaho. Drought conditions are expected to persist south of the Panhandle. Currently, ~72% of Idaho lands are experiencing moderate to extreme drought conditions according to the U.S. Drought Monitor.
Streamflow, snowpack, and precipitation data for each basin can be accessed on the NRCS Idaho Snow Survey web page.
For information on specific basins, streams, and reservoirs, you can view the full report below.