Big snowpack but no threat of flooding

The snowpack in the Weiser River drainage recently reached 160 percent of average, one of the highest numbers in the state, but has since dropped to 145 percent due to warmer temperatures.

 February brought nearly non-stop precipitation for almost the entire month to southwest Idaho, which fell in the form of snow at the higher elevations. 

 The Weiser River basin received 325 percent of normal rainfall for the month, according to the most recent water supply report issued by the Natural Resources Conservation Service on March 1.

 In the Weiser River basin, all of the Snotel sites are above 100 percent of average for snowpack. 

 On Monday, the snowpack at Squaw Flat (6,240 feet) measured 174 percent of average at 102 inches of snow. It had been as high as 113 inches. 

 Bear Saddle (6,180 feet) on Monday was at 131 percent of average for the date with 89 inches of snow. The lowest Snotel site in the Weiser River drainage, Van Wyck (4,920 feet), was at 147 percent of average with 43 inches of snow. It had been up to 50 inches of snow.

 With all that snow in the mountains, the concern each spring turns to how quickly the snow will melt and if any flooding appears to be a possibility.

 The streamflow forecast from the NRCS for the Weiser River is 150 percent of average. With the abundant mid-elevation snow across many of the large valleys in these basins, streams have the potential to rise suddenly when warm temperatures arrive, the NRCS said.

 Flows on the Weiser and Snake rivers have increased and dropped over the past week but pose no threat of flooding. 

 “We’re not looking at any significant changes,” said Tony Buthman, who is the emergency management director for Washington County.

 The Weiser River rose to 8.32 feet on March 7, its highest level this year. It dropped back down to 6.47 feet with a flow of 2,260 cubic feet per second on Monday. Flood stage on the Weiser river is 9.5 feet, which is when some water could spill into lowlying farm fields.

 The Snake River at Weiser reached 5.93 feet on March 8. On Monday, it had dropped to 5.54 feet. Still, there is a lot of water flowing at 21,500 cfs. Flood stage on the Snake River is 12 feet.

 The Snake River is likely to flow slightly higher for a while as flood control operations start on the Boise River reservoirs, which include Anderson, Arrowrock and Lucky Peak reservoirs. 

 The Bureau of Reclamation, which operates the dam, is releasing water in the reservoir to make room for spring runoff.

 The Boise river empties into the Snake River near Parma upstream from Weiser. Higher flows on the Boise River will impact the Snake River. 

 The flow on the Boise was scheduled to increase from 208 cubic feet per second to 1,780 cfs, a gradual rise in 500 cfs increments over several days through March 8. 

 Locally, the higher flows on the Boise River shouldn’t have much of an  impact on the Snake River flows, Buthman said.

 “It’s going to increase the flow (at Weiser) just a little bit,” he said.

 The move to increase the runoff storage capacity at the Boise River reservoirs for flood control was prompted by the big jump in snowpack numbers in February.