Low winter snowfall, a dry spring and predicted warm and dry weather are shaping up to put the Wood River Valley into a drought this summer.
In its Idaho Water Supply Outlook Report for May, the Natural Resources Conservation Service noted that April precipitation was less than 75 percent of normal for the region.
“The absence of storm tracks in April did not help the Wood and Lost’s current abysmal water year,” the NRCS stated. “Persistently dry conditions continue to plague the Wood & Lost basins.”
SNOTEL sites in the Big Wood basin this week average 43 percent of normal snow-water equivalent. For the Little Wood Basin, it’s only 17 percent and for the Big Lost Basin it’s 15 percent.
The NRCS stated that by the beginning of May, SNOTEL sites below 6,500 feet had completely melted, with a few sites completely melted at about 7,500 feet in the Pioneer and Boulder Mountains.
The Big Wood River at Hailey is projected to run at about 40 percent of normal this spring and summer. However, the poor water supply forecast is somewhat mitigated by above-average water storage in local reservoirs. According to the NRCS, at the end of April, Magic Reservoir held 157,000 acre-feet of water; normal is 128,000 acre-feet. The Little Wood Reservoir held 29,000 acre-feet; normal is 25,000 acre-feet.
By combining streamflow forecasts with reservoir storage, the Surface Water Supply Index provides a more comprehensive outlook of water availability. Its values are scaled from plus 4.0 (abundant supply) to minus 4.0 (extremely dry), with a value of zero indicating a median water supply compared to historical occurrences. The current index value is minus 1.3 for the Big Wood Basin and minus 2.1 for the Little Wood and Big Lost basins.
Water District No. 37 Water Master Kevin Lakey said in an interview that southern Blaine County irrigators will probably have to shut of their water earlier than normal this year so that water can be delivered to downstream irrigators with more senior rights, but that Bellevue Triangle farmers have supplemental wells they can turn to during droughts.
“They’ll all be able to finish most of their crops that they would normally finish,” Lakey said.
Snowpack this winter was better farther north. In the Salmon River basin, it stands at 74 percent of normal this week, and even farther north in the Clearwater Basin, it’s 100 percent.
The NRCS stated that the Salmon River is on track to peak in late May or early-June.
Sawtooth National Forest Fire Management Officer Matt Filbert said it’s still early to make detailed predictions, but he’s expecting a normal to above-normal wildfire season.
In the southern part of Blaine County, plentiful moisture last year allowed grass to grow tall, Filbert said, but little snow this winter means it didn’t get compacted; when it’s tall, it’s more flammable. Farther north in the forested portions of the county, the combination of low snowpack and little rain is allowing dead fuels to become drier.
“If we stay on this trend, by July 1 we’ll be in pretty severe conditions,” he said.
The National Weather Service’s outlook through August is for above-normal temperatures and below-normal precipitation. Information posted by the Great Basin Coordination Center, which mobilizes resources to fight wildfires, includes a drought monitor showing south-central Idaho in a moderate to severe drought. That drought is predicted to persist or intensify through July.