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United States Department of Agriculture
Natural Resources Conservation Service
9173 W. Barnes Dr., Suite C
Boise, Idaho 83709
 
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Ron Abramovich, 208/378-5741
Phil Morrisey, 208/685-6983
 

Too Much or Too Little?
June Water Supply Outlook Report for Idaho by Cindy Snyder for the NRCS

Boise, Idaho, June 6, 2008 – Boise, Idaho (June 6, 2008) --  Too much or too little sums up Idaho’s water supply picture for this year. While there is still more runoff to come in northern Idaho and the upper Snake basins, streams in southern Idaho and central Idaho are on the downhill side.

Record high runoff volumes in May on the Coeur d'Alene River and near  record low February-May precipitation in the Big Lost illustrates the variable climate and precipitation  patterns in Idaho this year, said Ron Abramovich, a hydrologist with the USDA Natural Resources Conservation Service in Boise.

June 1 snowpacks range from 100 to 200 percent of average in the Panhandle, Clearwater, Salmon and Upper Snake basin in eastern Idaho and western Wyoming. These are the places where the streams will rise one more time, but only the streams in the Upper Snake have enough snow remaining to exceed the previous peak set May 20.

May streamflow in the North Fork Coeur d'Alene River at Enaville was record high at  747,000 acre-feet, nearly the 30-year average of 780,000 acre-feet for May through September. The previous record high at Enaville was 637,000 acre-feet set in 1997.

“May basically delivered the spring and summer water supply in one month on the Coeur d’Alene River,” Abramovich said.

On the dry side, streamflow forecasts took a plunge in the Big Lost basin and are now forecast at 66 percent of average for the June-September period. Not surprisingly, the Wood and Lost basins have also received the lowest precipitation amounts for this water year.  The Lost-Wood Divide SNOTEL site just east of Sun Valley has received 22 inches of precipitation since October 1, Abramovich said. The average is 27 inches. This is the eighth lowest amount of precipitation to fall in the October to May period since 1982.

Surface water irrigation supplies will be tight for the Bear, Big Wood, Little Wood, Big Lost, Little Lost, and Salmon Falls water users due mostly to lack of precipitation in recent months, windy conditions and inefficiency of the snow to produce streamflow. Users should consider using the smaller runoff volume forecasts for their decision making purposes in these basins if they haven't already. 

Future temperatures are still the key in how the remaining snow melts. A return to hot weather, as observed in mid-May when streams across the state roared to peak levels would boost streamflows from the remaining snow with the exceptions of the Boise, Wood, Lost, and basins south of the Snake River including the Bear. Continued moderate or normal temperatures will allow the remaining snow to gradually melt and sustain streamflows as observed in the Owyhee and Bruneau rivers.

"Idaho's whitewater rafting season is off to a great start", Abramovich said. Stream flows will be dropping to safer floating levels as the snow runs out and provide an extended river running season.

The complete NRCS June 1 Water Supply Forecast Report for is available at: http://www.id.nrcs.usda.gov/snow/watersupply/.  The report provides a summary of snowpack conditions, precipitation, reservoir storage, and forecasted streamflows at monitoring points in each major basin in the state.

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