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NEWSUnited States Department of Agriculture
BOISE, June 6, 2003—Record high temperatures in late May jump-started the melting of Idaho’s high elevation snowpack, resulting in many streams reaching their peak flows on May 31 and moving the water into many reservoirs. Streamflows are now dropping quickly, and high elevation snowpack has essentially melted out for the season, according to the Idaho Water Supply Outlook Report issued June 1 by the Natural Resources Conservation Service. Streamflow forecasts for the June-July season vary with the remaining snow and elevations. The highest forecasts are from 100 to 113 percent of average for Smith Creek, Selway River, Lochsa River, Clearwater River at Spalding, Salmon River at White Bird, Deadwood River, Lake Fork Payette River, North Fork Payette River, and Little Wood River. The lowest streamflow forecasts in the state are 8 percent of average for
the Blackfoot River and Bear River below Stewart Dam. Blackfoot and Oakley reservoirs are only 25 percent full, 35 percent of average. Owyhee and Bear Lake reservoirs are 30 percent full and 37 percent of average. Salmon Falls Reservoirs remains the lowest in the state at only 15 percent full, 28 percent of average, the 9th lowest May 31 storage since 1922. Above average snowpack in the Selway basin should help maintain summer flows, which is good news for recreationists. Drafting of reservoirs will start as inflows decrease below irrigation demand. Most southern Idaho reservoirs will be at or near their minimum storage levels by summer’s end. NRCS continuously monitors mountain snowpack, precipitation and temperatures
throughout the year. In the West where snowmelt provides about 75 percent of the
water supply, NRCS and the National Weather Service coordinate and publish
streamflow forecasts from Jan. 1 through June 1. The latest snowpack and water
supply information is available on the NRCS Idaho website at
www.id.nrcs.usda.gov/snow. Panhandle Region: Streamflow forecasts range from 69 percent of average for the Coeur d’Alene River to 100 percent for Smith Creek. Surface water supplies should be adequate to meet most water needs. Clearwater River Basin: The Selway and Lochsa Rivers are forecast at 111 percent of average for the June-July period. Dworshak Reservoir Inflow is forecast at 84 percent of average. Salmon River Basin: Streamflow forecasts for the Salmon River at Salmon is 90 percent of average and 104 percent for the Salmon at White Bird. Weiser, Payette, Boise River Basins: Streamflow forecast for the Payette River near Horseshoe Bend is 96 percent of average. The Boise River near Boise is forecast at 90 percent of average, and the Weiser River at 92 percent of average. Crane and Mann Creek reservoirs filled and should provide adequate irrigation water. Rangeland is in good shape as a result of spring precipitation. Wood and Lost River Basins:
Little Wood Reservoir is full and forecast at 105 percent for the rest of the
runoff season. Streamflow for Mackay Reservoir is for 79 percent of average.
Water supplies will be short in the Little Lost, Big Wood, and Big Lost basins. Southside Snake River Basins: Salmon Falls and Oakley reservoirs are 55 percent and 60 percent of average. Both are storing less water than last year. Owyhee Reservoir is 31 percent of capacity, 26 percent of average. Streamflow forecast for Salmon Falls Creek is 23 percent of average. Bruneau River is 29 percent. Owyhee River is 28 percent and Oakley Inflow 22 percent. Irrigation agricultural water shortages will be felt the hardest across these southern Idaho basins and the Bear River basin this summer. Bear River Basin: Reservoir storage is 411,900 acre-feet, the third lowest May 31 storage since 1921; only 1935 and 1936 were less. Bear Lake is projected to be at record low levels later this summer. With the Bear River near Stewart Dam forecast at 9 percent of average, water shortages will be more severe than last year.
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