Idaho Water Supply Outlook IDWR State Water Supply Meeting Jan 11, 2013

Summer 2012 Fires Trinity Ridge (Boise Basin) 147,000ac Long Draw (Owyhee Basin) 350,000ac Jacks (Owyhee/Bruneau Basins) 51,000ac Idaho led the nation in acres burned with 1.7 million acres.

Hydrologic Fire Effects: Earlier snowmelt & runoff Forest Fire Impacts on Snowmelt Rates Atlanta Summit vs Jackson Peak for 2000 and 2004

New Normals this Year Every decade the 30 year normals change periods. This year we go from the period to the period. The change is meant to keep pace with current climatic conditions as most recent years are said to represent the current conditions. Most data types will be calculated as a straight average except Snow Water Equivalent which will be the “median” or “middle value”

Trade 7 big years for 9 low years Apr-Sep Volumes: average = 1,526 KAF average = 1,363 KAF Compare 2012 runoff of 1,600 KAF 105% of average 117% of average +12%

Old vs New Normals Trade 7 big years for 9 low years average = 39.5” median = 35.3” Compare 2012 snowpack of 37.9” 95% of average 107% of average +12%

Why will SWE use a median?

Water Year Precipitation Oct 1 – Jan 8

Idaho Water Year Precipitation Oct 1 – Jan 8

Snowpack as of Jan 8

Idaho Snowpack as of Jan 11

Snow Water % of Normal as of Dec 5 th Storms brought several feet of snow in Central Idaho Mountains

+ and – are Near Record High Snow above 6,881 feet: Deadwood Summit Lost-wood Divide Bear Canyon Stickney Mill + and – are Near Record Low Snow below 6100 feet: Cozy Cove Graham GS Bogus Basin

2013 Snowpack trends Long range experimental NCEP’s Climate Forecast System Max SWE model compared to current Jan 8, 2013 conditions

This region has already received over 57% of annual precipitation 2012 annual precipitation was 123% of average. Above normal Fall precipitation primed soils and brought streams to above average levels.

Forecast range 39 to 113 to 190% 2012 runoff 80%

Dec 31, 2012 storage 28.3 KAF average Dec 31 = % average Dec 31 = %

Forecast range 76 to 100 to 124%

2012 runoff 21%

The graphs above, make 2012 look like a normal year, but the way the snow fell, melted with 90F temperatures in early April followed by 1-2” of rain in late April and minimal summer precipitation was anything but normal…. Let’s hope 2013 is a little more normal with these new normals. Questions/Comments