For the week of Nov 27 - Dec 3, 2002

Water year off 
to dismal start

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Idaho snow facts

Melting snow produces more than 75 percent of Idaho’s water. The other 25 percent comes from spring and summer rains.

The National Resources Conservation Service, based in Boise, uses 78 automated SNOTEL stations and 100 manually measured snow courses to collect information about the amount of snow and its water content.

The oldest sites began monitoring in the 1990s in Yellowstone National Park and northern Idaho.

Some more tidbits:

• The amount of new snowfall it takes to equal 1 inch of water is about 10 inches.
  
  

• The deepest snow ever measured in Idaho was 23.5 feet at Lost Lake in Shoshone County on April 1, 1974.
  
  

• The greatest amount of water ever measured in an Idaho snowpack was 9.75 feet at Bear Mountain in Bonner County on May 1, 1974.
  
  

• Idaho’s two snowiest places, receiving more than 50 feet of snow each year, are Bear Mountain in Bonner County and Lost Lake in Clearwater County.
  
  

• Idaho’s least snowy place is Grand View in Owyhee County, recieving 7.2 inches of snow each year.
  
  

• The wettest winters on record in Idaho are 1997 in the Upper Snake River Basin and 1965 and 1974 in Central and Northern Idaho.
  
  

• The driest winters on record in Idaho are 2001 in Northern Idaho and 1977 and 1992 in Southern Idaho.

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By GREG STAHL
Express Staff Writer

While most of the Eastern United States has wallowed in rain and snow this fall, Idaho and most of the Pacific Northwest are severely parched and without a significant quenching in sight.

According to the Natural Resources Conservation Service the lack of summer and fall precipitation has taken its toll on Idaho’s water supply, and the new water year is off to a poor start. October precipitation was far below normal, with the lowest amount at 25 percent of average across western and northern Idaho and 87 percent of average in Southeast Idaho’s Bear River basin.

Several Idaho rivers are at or near record low flows for early November, including the Weiser, Bruneau, South Fork Payette, Little Wood, Portneuf and Lower Bear rivers.

Monday, the Big Wood River in Hailey was about 40 cubic feet per second higher than average for this time of year.

Most of the state’s reservoirs are also extremely low, and Magic, Mackay, Salmon Falls and Oakley reservoirs are nearly empty.

The bad news is that several wet years are needed to fill reservoirs and to recharge soil moisture, springs and wetlands, said Ron Abramovich, NRCS water supply specialist.

The worse news is a weak to moderate El Nino is forecast to sear weather patterns in the Northwest this winter.

"It took three years of below normal snowfall to get to this critical point in the drought, and it may take several years to get us out," said Abramovich. "Near normal or better snowpacks are needed by April 1 to provide adequate irrigation water next summer."

Abramovich said that, because of groundwater deficiencies, a 113 percent of average snowpack is needed above Palisades Reservoir on the Snake River just to produce a 90 percent of average stream flow.

"The minimum snowpack percentage needed is based on observed runoff for other years that followed droughts and the inefficiency of the snow to produce streamflow," said Abramovich. "For example, a snowpack of 96 percent on April 1, 1989, in the Big Lost basin resulted in a summer stream flow of only 40 percent of average."

Historically, El Nino patterns have favored wetter-than-normal winters in the Southwest and drier than normal winters in the Pacific Northwest, Abramovich said.

He explained that El Nino represents a shift in the odds in obtaining various amounts of winter precipitation in Idaho. For the Snake River basin, El Nino events since 1934 have resulted in streamflows greater than 90 percent of average 12 out of 21 years.

 

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