How far downstream do wildfire disturbances propagate in fluvial networks?

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Devastating wildfires are increasing in frequency and severity across the Western and Southwestern United States. In addition to the dramatic impacts of wildfires on infrastructure, soils, and terrestrial ecosystems, there is growing evidence that wildfires trigger cascading disturbances that propagate across fluvial networks and watersheds impacting water quality and ecosystem services in aquatic environments. However, there is a critical lack of data, modeling tools and fundamental knowledge to assess how far downstream wildfire disturbances propagate in fluvial networks and the extent to which they affect water quality, ecosystem services, and downstream hydrological processes such as flood attenuation by riparian vegetation and groundwater recharge by infiltration. The overarching goal of this research is to address these gaps in our fundamental understanding of the impact of wildfires. To advance this goal, the Principal Investigators (PIs) of this project propose to setup, train, and maintain Rapid Response Teams (RRTs) capable of deploying in-situ sensors to investigate disturbances to watersheds following wildfires and assess changes in water quality before and after wildfires. The successful completion of this research will benefit society through the generation of new data and modeling tools to predict and assess the impact of wildfires on water quality and aquatic ecosystems. Further benefits to society will be achieved through student education and training including the mentoring of a postdoctoral associate, one graduate student and two undergraduate students.In the United States, wildfires are increasing in frequency, severity, and extent. While we currently have the capability to map fire areas and their severity with relatively high accuracy using areal and satellite images, we do not have comparable capabilities to map the extent of wildfire disturbances across fluvial networks and watersheds. This project will address two fundamental questions about the impact of wildfires: 1) how far downstream do wildfire disturbances propagate in fluvial networks, and 2) what are the key controlling factors? To answer these two questions, the Principal Investigators (PIs) of this project propose to leverage the combined advantages of Eulerian monitoring (fixed sensors at a site) and Lagrangian monitoring (mobile sensors that move with a water stream) by deploying Rapid Response Teams (RRTs) and networks of in-situ sensors to investigate changes in water quality [e.g., pH, turbidity, dissolved oxygen, dissolved organic matter (DOM), and nutrients (e.g., nitrate)] before and after wildfires. The data collected by the RRTs will be analyzed and interpreted using GIS watershed geomorphology data, land use and land cover data, spatiotemporal statistical analysis of water quality data, and water quality modeling. By combining these data, methods and modeling tools, the PIs hope to develop a framework to generate scaling relationships capable of predicting how far downstream wildfire disturbances propagate in fluvial networks and the extent to which they affect water quality, ecosystem services, and critical downstream hydrological processes such as infiltration, flood attenuation and groundwater recharge.This award is jointly funded by the Environmental Engineering and Environmental Sustainability programs of the NSF/ENG/CBET Division.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.