BOISE, Idaho (KIFI/KIDK) - A La Nina weather pattern has had a significant impact on Idaho's water supply outlook this winter.
USDA's Natural Resources Conservation Service (NRCS) reports the pattern continues to bring moisture to the basins north of the Salmon River while central and southern Idaho have been drier than normal. Mountains along the Montana border to the Snake River headwaters of Yellowstone National Park in Wyoming are benefiting with a near normal or better snowpack.
Reservoirs are benefiting from carryover storage from last year as well as above normal winter streamflow that is still filling reservoirs. NRCS said more snow is needed to mitigate the impact of snow drought across southern Idaho, improve winter recreation, and help sustain flows later this summer. Water managers have not yet determined how best to manage water release. The agency said there should be adequate irrigation supply in the Boise, Upper Snake, Bear, Oakley, Salmon Falls, and Owyhee basins.
As of February 1, snowpacks range from 110 percent of normal in the Clearwater basin, 199 percent in the Lemhi basin, and 120 percent in Pacific Creek and Buffalo Fork in the Upper Snake in Wyoming. The Snake above Palisades is 107 percent of average, the Snake above American Falls is 96 percent.
Reservoir storage remains at relatively high levels. In the Upper Snake, Palisades Reservoir is 97 percent full and 148 percent of average. Jackson Lake is 78 percent full and 152 percent of average. Together, the region's reservoirs are 89 percent full and 150 percent of average. That is the second highest January 31 storage level since Palisades was built in 1955. Ririe Reservoir is 58 percent full and 122 percent of average, Blackfoot Reservoir is 81 percent full at 154 percent of average and American Falls Reservoir is 86 percent full and 129 percent of average. American Falls is currently releasing 7,200 cubic feet per second.