BOISE—Idaho water experts are using the term “snow drought” to describe the state’s water year to date.
Since the start of October, precipitation has been near normal across Southern Idaho, including in the Owyhee, Bruneau, Salmon Falls, Oakley and Upper Snake basins. But far too little moisture has fallen as snow, and unseasonably warm winter and early spring temperatures prematurely melted low- and medium-elevation snowpack.
Many major reservoirs are nearly full following a May that brought 250 percent of average monthly precipitation to parts of Southern and Eastern Idaho, according to the final USDA Natural Resources Conservation Service moisture report of the season. The Boise reservoir system is now 93 percent full, and Jackson Lake and Palisades Reservoir in the Upper Snake system have 125 percent of their average fill to date. Salmon Falls Creek Reservoir and Magic Reservoir water managers were able to shut off irrigation flows during much of May and accumulate more storage, to the point that Salmon Falls returned to its seasonal peak storage volume.
Before May, Lyle Swank, watermaster of the Upper Snake water district, said many users were concerned about running out of water before finishing even their grain crops.
“I don’t think you have that same concern any more,” Swank said.
Nonetheless, more of Idaho has been added to a drought map as May precipitation largely missed Northern Idaho, which received 40 to 60 percent of its normal monthly moisture, and a lack of mountain snowpack has natural flow forecasts ranging from 20 to 70 percent statewide.
Tim Dillin, who farms in Bonners Ferry, said his grain and hay have matured two weeks early due to hot and dry weather in Northern Idaho. He was concerned the dryness would harm his spring wheat, until a timely rain arrived at the end of May.
Ron Abramovich, Idaho’s NRCS water supply specialist, said 55 of the 137 snow survey sites in and around Idaho would normally retain snowpack by this time of year, but only 16 sites still had snow as of June 1. Abramovich anticipates shortages will occur in the Oakley, Salmon Falls, Owyhee, Big Wood, Little Wood, Big Lost and Little Lost basins.
“Our money supply in terms of stream flows isn’t there this year,” Abramovich said, adding minimal inflows into reservoirs this summer will result in low storage carryover into next year.
Upper Snake River flows at the critical Heise gage are projected to be 62 percent of normal through September. Little Wood Reservoir is two-thirds full but is projected to run out of water by late July for a second consecutive season, Abramovich said. Mackay Reservoir is 80 percent full, but its irrigators face similar or worse shortages as last year due to low inflows. The Payette River reservoir system filled in early June, but is projected to have the sparsest runoff since 2007.
Abramovich said June precipitation has been near normal thus far throughout most of Idaho, and the 90-day outlook calls for better odds of wetter and warmer weather than normal, with the continuation of a pattern of moisture arriving from the southeast.
Source: www.capitalpress.com