Identifying the need for fire-water decision-support tools for water managers in the Pacific Northwest, USA

Abstract:

Many drinking water utilities in the Pacific Northwest (PNW) depend on forested watersheds to provide clean water supplies for the millions of customers they serve. With fire disturbances in the PNW projected to increase with regional climate change, these forested watersheds could experience significant increases in erosion, runoff, suspended sediment, and debris flows. Such sudden, substantial water quality degradation after fires would be a major challenge for water utility operations. Yet little information or empirical data about post-fire impacts to drinking water in the PNW currently exists, hindering the ability of water utilities to plan effective short-term wildfire responses or longer-term recovery strategies. Decision-support modeling tools that leverage remote sensing data could greatly aid water managers by integrating relatively static geographic characteristics (e.g., slope, soil type) with relevant, updatable data from Landsat and SMAP to predict areas of fire risk and post-fire watershed responses (e.g., erosion, sediment loads). A needs assessment was conducted to collect information from water managers across the PNW to identify 1) key concerns about wildfire impacts to surface water supplies, 2) existing strategies used to respond to or prepare for fires, and 3) the information or tools that would be most valuable to managers when making wildfire risk and response decisions. Results from focus groups with twelve utilities- in total representing nearly six million customers- and a broader PNW-scale survey revealed several water utility concerns about post-fire water quality impacts. Specifically, utilities voiced the need for tools that could help predict where watersheds are most vulnerable to wildfire events and how they may change post-fire. Many participants emphasized that a helpful tool would allow them simulate fire events to evaluate the impacts of different management responses for reducing the likelihood of fires and quantify water quality impacts at the watershed scale. The results from this needs assessment are being used to create a decision support tool from the FireEarth modeling framework, which couples fire spread, ecohydrology, and soil erosion models to characterize fire vulnerability and complexity for water managers across the PNW.