HR: 14:10h
AN: C33A-03    [Abstracts]
TI: Snowmelt, Summer Drought and Fires: Using Stream Gage Data to Extend Snowmelt Records in Fire-prone Areas of Central Idaho
AU: Pierce, J L
EM: jenpierce@boisestate.edu
AF: Boise State University, Department of Geosciences 1910 University Dr, Boise, ID 83725, United States
AU: * Kunkel, M L
EM: MelKunkel@mail.boisestate.edu
AF: Boise State University, Department of Geosciences 1910 University Dr, Boise, ID 83725, United States
AB: In Idaho, 2007 and 2006 were the warmest and third warmest (respectively) summers recorded since 1904. In 2007, high summer temperatures combined with severe drought conditions have led to one of the most severe fire seasons since the Yellowstone fires of 1988, and by September 1, severe fires continue to burn > 2 million acres. In snowmelt-dominated watersheds of Idaho, earlier snowmelt, the earlier onset of spring and subsequent dry fuels promote severe fire seasons. Data on the timing of snowmelt from National Resources Conservation Service (NRCS) Snow Telemetry (SNOTEL) sites, however, extend back <30 years, and placing recent droughts and fires within a historic context requires examination of a longer record. In order to examine relationships between timing of final snowmelt and summer drought and fire conditions since the early 1900s, we have developed techniques to infer the timing of final snowmelt from stream flow records. Long-term stream gage stations in Idaho were selected from the Hydro-Climatic Data Network (HCDN) and matched to nearby SNOTEL stations. We selected 15 HCDN gage sites within Idaho that had an average of 75 years of gage data, and were located in close proximity to the drainages of SNOTEL sites with at least 10 years of continuous snow water equivalent data through 2006. We used only gage data from the years that were complete 97% of the time or greater, >98% of all yearly data was usable. Missing data within years that met the 97% or greater level were estimated using linearly extended values between known values. Less than 0.05% of the data required estimation. Using a Short Term Fourier Transform (STFT) we computed the historic final snowmelt dates and compared the results with actual snowmelt dates from SNOTEL data. Computed vs. actual snowmelt dates were within +/- 4 days ~93% of the time and ~98.5% of the time within +/- 6 days for all years tested for the 15 selected gauge sites. This provided us with over 1100 yearly final snowmelt dates extended throughout Idaho. The extended final snowmelt dates where compared to nearby NRCS Snow Course data, extended dates corresponded well with the existing snow course values for all 15 sites. Ongoing research compares the extended snowmelt data with historical fire seasons while focusing on the development of drying curves to be used with current final snowmelt dates as a predictor to the onset of fire conditions in Idaho. Future work will extend additional final snowmelt records in Idaho and other western US states and will examine relationships between final snowmelt dates and the onset of fire conditions in the western US.
DE: 1807 Climate impacts
DE: 1833 Hydroclimatology
DE: 1860 Streamflow
DE: 1872 Time series analysis (3270, 4277, 4475)
SC: Cryosphere [C]
MN: 2007 Fall Meeting