Water Resources Research Act Program

Details for Project ID 2018WA434B

Washington wildfires disrupt water quality: Are drinking water systems resilient to climate change?

Institute: Washington
Year Established: 2018 Start Date: 2018-03-01 End Date: 2019-02-28
Total Federal Funds: $27,500 Total Non-Federal Funds: $55,013

Principal Investigators: Amanda Hohner, Jan Boll

Project Summary: Fire-prone forested watersheds generally provide high quality water for downstream communities. Climate change influences are tied to the marked increase in wildfire activity in Washington State, western North America, and other regions globally. Wildfires can influence both water quantity and quality, and water providers must confront the challenge of adapting to a dramatically altered watershed and disrupted water supply. Currently, there is a lack of post-fire source water quality and treatability information available for Washington State water purveyors facing recent unprecedented wildfire seasons. Such information is essential to support decision-making and effective management of post-fire threats to drinking water quality. Our goal is to quantify and characterize the water quality and treatment concerns following the 2017 wildfire season in Washington. The Norse Peak wildfire recently burned the eastern slope of the Central Washington Cascade Mountains, including 22,625 hectares of the Naches River watershed. The City of Yakima depends on the Naches River for their primary source of drinking water. Our approach is to partner with the City of Yakima Water/Irrigation Division to explore raw source water quality at the Naches River water intake, pre- and post-fire. The watershed is characterized by steep slopes vulnerable to soil erosion, which will likely be enhanced following the fire. Spring runoff and flooding can cause high particle levels (i.e., turbidity), which the current Naches water treatment plant cannot effectively process. Post-fire runoff may also contain elevated natural organic matter (NOM) levels, which can react with chlorine to form toxic disinfection byproducts (DBPs). Water treatment plants must reduce NOM to meet DBP regulations under the Safe Drinking Water Act. The effects of the Norse Peak fire will likely heighten existing pressures on Yakima’s water system, including particle removal, solids processing, and DBP formation. We will leverage existing historical monitoring data to characterize pre-fire water quality for the water intake. In addition, we will conduct a field-based sampling campaign of the Naches River intake during the 2018 snowmelt and runoff season to supplement existing monitoring frequency, and expand analytical measurements through more advanced analyses. Samples will be characterized for post-fire changes in turbidity, nutrients (N, P), NOM quantity and quality, and DBP precursors. Additionally, a bench-scale treatability study will be used to address process performance (i.e., conventional coagulation, direct filtration) challenges and finished water quality implications (i.e., DBP levels). Our work has the potential to engage stakeholders and researchers in hydrology, ecology, forestry, water quality, and engineering. We will provide Washington communities with a knowledge base and recommendations founded on science to prepare for degraded source water quality following a wildfire. The project will provide partial support for one MS graduate student and will serve as a chapter in the student’s thesis, which will be submitted to a peer reviewed journal, such as Water Research. The graduate student will present project findings at the 2019 American Water Works Association Pacific Northwest Section conference. This project supports the mentoring of an early career researcher by a senior faculty, and serves to kick-start the PI’s future research strategy.