Understanding the Impact of Climate Change on Nitrogen Sources and Water Quality in Rivers of Western Washington

Forest stream

    NW CASC Fellow

  • Elizabeth Elmstrom, University of Washington, elmstrom@uw.edu
  • Faculty Advisor

  • Gordon Holtgrieve, University of Washington, gholt@uw.edu

The hydrology of the Pacific Northwest is strongly driven by cool season precipitation and snowpack melt. Such hydrologic conditions govern aquatic ecosystem functions and water quality through the supply and transfer of nutrients. Climate models predict that substantial winter warming will increase precipitation falling as rain and decrease snowpack, leading to increased winter river runoff and reduced summertime flow. These altered hydroclimatic conditions are likely to affect the sources of the nutrient nitrogen that is delivered to rivers and receiving coastal waters.

Nitrogen’s role in water quality is multifaceted. Although nitrogen is critical to ecosystem functions, excess nitrogen becomes a regulated pollutant and has been linked to local eutrophication and increasing ocean acidification. With little existing information on the sources of nitrogen in Puget Sound rivers, the purpose of this project is to understand how projected hydroclimatic conditions will affect riverine and coastal ecosystem health. This work will leverage stable isotopes to establish current sources of nitrogen across Puget Sound watersheds, and in combination with climate change scenarios and numerical models, project how hydroclimate will translate to water quality. This analysis could be used to help managers develop responses that build ecosystem resilience in the face of accelerating environmental change.