NRCS FORECASTS RECORD SNOWMELT RUNOFF

Snow Water Content Highest In 40 Years, Will Result In Increased Volume in Some Rivers

April 20, 2005 (Palmer, AK) - The surprise spring snowfall this week will only increase the record-setting snow depth and water content measurements set across the state this year, according to Richard McClure, hydrologist who directs the Snow Survey program for the USDA Natural Resource Conservation Service (NRCS).

As of April 1, nine NRCS Snow Survey courses broke snow water content records established as long as 40 years ago. The nine courses are located at Seven Mile (Central Yukon basin), Lake Todatonten and Thirty Mile (Koyukuk basin), McGrath (Kuskokwim basin), Tozikaket  (Lower Yukon basin), Horsepasture Pass (Copper basin), and the Dutch Hills, East Fork Chulitna and Monahan Flat (Upper Susitna basin).

In addition, seven NRCS Snow Survey courses located in the Innoko Wildlife Refuge exceeded all snow water content measurements since data started being recorded in 1996. Two snow courses located in Canada’s Yukon Territory also exceed previous snow water content records established 30 years ago. 

This increase of snow might be good news or bad – depending on how you look at it.

According to McClure, the impact of snow depth and melt projections could range from more difficulty catching King salmon in the Deshka River, to later planting dates for interior farmers. 

Deep snowpacks are bad for moose that become more susceptible to predation by wolves and brown bears. But the snow has been great for recreationalists this winter and will extend the snow machining and skiing season into May.

Snowpacks that are 30 percent above normal in areas burned by last summer’s wildfires will probably result in a good amount of soil erosion because of the dearth in vegetative cover.  On the other hand, the snow might help delay the fire season and reduce the potential wildfire outbreaks. 

“While some people in Anchorage or Mat-Su might have experienced a rather mild winter, many parts of the state will see river flows from snow melt that are much higher than normal,” said McClure.

In the central Yukon region, the volume flow forecast for the Yukon River near Stevens Village is 116 percent of normal for the period of April through July.  At this rate, enough water will flow through this area to cover 48,200,000 acres with one foot of water – a measurement known as acre-ft.

The April through July flow on the Kuskokwim River at Crooked Creek is forecast at 12,400,000 acre-ft, which is 118 percent of normal flow. The Talkeetna River is forecast to flow at 129 percent of normal – or 2,100,000 acre-ft from April through July. The forecasted flow for the Yukon River at Eagle is 117 percent of normal flow for the period of April through July, or 40,000,000 acre-ft.

Rivers that no longer have gauging stations to measure acre-ft use the Snowmelt Runoff Index – a scale of measurement from -3 to +3, with 0 being normal water flow rates.  A rating between +2 and +3 means runoff will be 30 to 50 percent above normal.

Susitna Valley streams will be some of the hardest hit by snowmelt runoff.  The Susitna River at Gold Creek is forecast at +2.9; Chulitna River near Talkeetna +2.8, Deshka River at the mouth near Willow +2.4, Montana Creek at Parks Highway +2.3, Willow Creek near Willow +2.7, and Skwentna River at Skwentna +2.5.  All these streams will be at or near their maximum of record for snowmelt runoff.

For the Koyukuk River at Hughes, the Snowmelt Runoff Index is +2.3. 

With the delay of warmer weather, the potential of ice jam floods increases along the Yukon and the Kuskokwim Rivers.  The three contributing factors for flooding are ice thickness, snowmelt runoff volume and spring weather. If weather warms up gradually, the breakup should cause less flooding; if it stays cool and then warms up very quickly or if it rains on top of the snow, the probability of flooding increases. The National Weather Service River Forecast Center is forecasting breakup to occur up to 7 days later than normal. 

In Southeast Alaska, where snowpacks are lighter than normal, towns that have hydro-electric power plants have very little energy in the form of snow water stored.  They will have to rely more on their diesel generators. 

More specific regional information, reports, and a map of NRCS Snow Courses is available at http://www.ak.nrcs.usda.gov/snow/index.html.

The Natural Resources Conservation Service puts 70 years of experience to work in assisting people to conserve, maintain, and improve our natural resources and environment. NRCS works in partnership with local conservation districts serves almost every county in the nation, and the Caribbean and Pacific Basin. Participation in NRCS programs is voluntary.

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