Take Home Message

Snowpacks will continue to offer winter recreation through the study period (2070) but with shorter seasons and loss of low elevation sites.

Key Findings

  • Snow depth for all recreational sites in the basin declines in the warm-wet and hot-dry scenarios, but remains fairly stable in the low-change scenario.
  • The day of year when the snowpack reaches its maximum depth shifts earlier in the year from a historical average of early March to late January by late century under the hot-dry scenario.
  • Based on this, it is reasonable to expect shorter winter recreation seasons and transitions to summer based activities earlier in the year, particularly at low elevation sites.

Background

Winter recreation is an important economic driver in the Big Wood Basin, particularly in the upper basin where businesses have developed to support lift assisted downhill, nordic, and in more recent years, backcountry skiing. Snowpack for winter recreation is heavily influenced by ‘snow covered area’ that is, what areas in the basin covered in snow, and the depth of that snow. The goal of this study was to understand how water supplies and timing would shift in the basin under a changing climate, and as a result, concerned itself primarily with the water content of the basin’s snowpacks, expressed as ‘snow-water equivalent’’ or SWE. To make this information useable for recreation planning, we have converted the snowpack’s water content to estimate snow depth based on approximations provided by Natural Resource Conservation Service’s, Idaho Snow Survey Program*. We make these conversions at a few locations identified as important, or representative of winter recreation in the basin. These include Sun Valley Resort at Mt. Baldy averaged across an elevation of 6400-9000 ft.; the ’Valley Floor’ generally representative of the nordic trails north of Ketchum between 5000-6400 ft.; Galena Snotel, representing nordic trails near Galena Lodge around 7500 ft., and Galena Summit Snotel, representing backcountry ski touring terrain at 8800 ft.

The results below show some of the results related to recreation.

The top chart represents four hydrographs: the historic (black) low change, warm and wetter, and hotter and drier than historical conditions. Under the low change scenario this is a shift in the timing of flows but still has a strong spring time peak flow. In the warm/wet scenario, timing of peak flow is diminished and occurs earlier in the year as a result of more volume running off during winter. The hot/dry scenario indicates a basin that is primarily rain driven, where precipitation falls primarily as rain with little stored as snowpack.

Snow Depths - December 15

 

Snow Depths - Winter Average

 

Maximum Snow Timing


* To convert SWE to snow depth we divide SWE by the snow density under the assumption that snow density in the Big Wood Basin is as follows in any given year: December 1 = 0.15, January 1 = 0.20, February 1 = 0.25, March 1 = 0.30, and April 1 = 0.35. As an example, a site that has 15 inches of SWE in February can be converted to depth by dividing 15 inches by 0.25, which gives us an estimated 60 inches of snow depth.




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