Water Resources Research Act Program

Details for Project ID 2015WA394B

Climate Change Effects on Water Supply: Linkages Between Wildfire and Accelerated Snowmelt

Institute: Washington
Year Established: 2015 Start Date: 2015-03-01 End Date: 2016-02-28
Total Federal Funds: $27,500 Total Non-Federal Funds: $55,000

Principal Investigators: Susan Kaspari, Carey Gazis

Abstract: In Washington State the majority of runoff comes from the melting snowpack. In recent decades, reductions in the seasonal snowpack have caused earlier runoff and decreased discharge, affecting the availability of water resources. A consequence of the earlier snowmelt is an increase in wildfire frequency, size, intensity and duration. This increase in fire activity affects snowmelt because decreased forest canopy in the post-fire environment causes an increase in snowpack net radiation, increasing the rate and further advancing the timing of snowmelt. Recent research has demonstrated that the deposition of burned woody debris (charcoal and charred needles, cones and bark) from charred snags (dead trees) on the snowpack reduces snow albedo (i.e., reflectivity) and further accelerates melt. However, it is not known how this effect attenuates over time, how it varies with burn severity, or how black carbon (a dark absorptive particle produced by the incomplete combustion of bio and fossil fuels, and commonly referred to as soot) from the charred snags contributes to the snow albedo reductions. We propose to quantify the duration and magnitude of earlier snowmelt in the post-wildfire environment. In forest plots of varying burn severity and burn age in the Eastern Cascades, we will measure snow albedo, snow water equivalent, forest structure, and black carbon, charcoal and burned woody debris deposition during the snow accumulation and snow ablation seasons. Study sites include the 2006 Tripod, 2012 Table Mountain, and 2014 Snag Canyon Fires, allowing this effect to be studied between 0.5 and nine years post-fire. The burn areas of the 2012 Table Mountain and 2014 Snag Canyon fires nearly intersected, providing an excellent opportunity to conduct a controlled experiment to quantify the temporal change in post-fire effects on snowmelt. By examining the linkage between impurity deposition, snow albedo, and snowmelt during the ablation period (including the date of snow disappearance), we will be able to assess how burn age and burn severity affects snowmelt, the timing of river discharge, and the availability of water resources. Climate models project continued reductions in the spring snowpack that will result in earlier snowmelt runoff, reduced summer flows, and a reduction in water supplies in Washington State. Additionally, the area burned by fire regionally is projected to double by the 2040s and triple by the 2080s. In light of the observed and projected changes to the snowpack and wildfire activity, an improved understanding of the linkage between wildfire activity and snowmelt is necessary to understand climate change effects on water resources. This research has broad stakeholder support to better understand how snowmelt dominated runoff is affected by wildfire in upland forests, and is particularly relevant for Washington State. The majority of wildfires in this region occur in the snow zone, with nearly half of snow zone wildfires in the Western United States occurring within the Columbia River Basin. This research addresses the USGS call for proposals related to climate change effects on water supply, demand, and quality.