Water Resources Research Act Program

Details for Project ID 2012WA344B

Response of River Runoff to Black Carbon in Snow and Ice in Washington State

Institute: Washington
Year Established: 2012 Start Date: 2012-03-01 End Date: 2013-02-28
Total Federal Funds: $27,000 Total Non-Federal Funds: $54,000

Principal Investigators: Susan Kaspari, Carey Gazis

Abstract: In the Cascade Mountains of Washington, most of the annual precipitation falls during the winter-spring and is stored in the snowpack. The majority of spring-summer runoff is derived from the melting snowpack, with glacier melt contributing as much as 50% to May-September runoff in watersheds with high concentrations of glaciers. Meltwater is relied on to refill reservoirs and to supply crucial summer flows to rivers used for fisheries, hydropower, irrigation, navigation, recreation and drinking water. In recent decades spring snowpack levels (snow water equivalent and snow extent) have decreased and glaciers have retreated, affecting the timing of runoff and availability of water resources. These trends are projected to continue in the future, which will put further stresses on the water supply. While previous work has largely focused on how changes in temperature and precipitation have and will affect runoff, another cause of accelerated melt may be the deposition of absorbing impurities (black carbon and/or dust) onto snow and glacier surfaces. The efficacy of absorbing impurities in accelerating melt has only recently begun to be investigated. A recent study in Colorado found that dust deposition has shortened the duration of the mountain snowpack by as much as 51 days. In the Cascade Mountains, the dominant absorbing impurity is likely black carbon from populated regions west of the mountains. Black carbon (BC) is a dark absorptive particle produced by incomplete combustion of fossil and bio-fuels. When deposited on highly reflective snow and glacier ice, BC causes darkening of the surface (i.e., albedo is reduced), resulting in greater absorption of solar energy, heating of the snow/ice, and accelerated snow and glacier melt. We propose to determine BC concentrations in snow in Washington State to assess if BC is accelerating snow and ice melt, and thus affecting the timing and availability of water resources. To do this, we will sample the seasonal snowpack every 1-2 weeks during the 2011-2012 winter at Blewett Pass (Central Washington), and collect snow and ice core samples during the spring-summer from the North Cascades, Mt. Olympus, and possibly Mt. Baker and Mt. Rainier. BC concentrations will be determined using a Single Particle Soot Photometer (SP2), and select samples will also be analyzed using a Sunset Lab OC-EC analyzer to compare methods. Albedo (i.e., reflectivity) reductions due to the presence of BC will be determined using calibrated reflectance panels, and by the relationship established from previous observational studies between BC concentrations and albedo reductions. This research will provide needed observational data of BC concentrations in snow and ice, which is the first step towards assessing the degree to which BC may be accelerating snow and ice melt. As a result, water resource and air quality managers will be able to make more informed decisions regarding potential controls on BC emissions, and identify alternative ways to help buffer the projected changes in water flows over the coming century. The proposed research will provide training and educational support for Ian Delaney, a MS student in the Department of Geological Sciences at Central Washington University advised by PI Kaspari, and addresses the USGS call for proposals related to climate change effects on water balances, stream flows, and water quality.