Post-Wildfire Water Quality Dynamics: A Multiscale Examination and Predictive Modeling of Stream Temperature and Turbidity in Western U.S. Watersheds

Wildfires, exacerbated by climate change and human activities, pose significant threats to water-related ecosystem services in forested watersheds. This dissertation investigates the multifaceted impacts of wildfires on stream temperature and turbidity, two critical water quality parameters essential for maintaining aquatic ecosystem health and human water uses. By integrating a comprehensive literature review, empirical data analysis, and advanced machine learning techniques, this research provides a nuanced understanding of how wildfires affect hydrological processes across various temporal and spatial scales. The findings reveal significant regional variability and the complex interplay between climatic, geographic, and anthropogenic factors. For instance, the literature review highlights the importance of fire severity, forest diversity, and human activities such as salvage logging in influencing post-fire water quality changes. Empirical data analysis across 101 burned watersheds in the Western U.S. over a 20-year period identifies local factors such as slope, canopy bulk density, and proximity to riparian areas as significant predictors of stream temperature trends. Advanced machine learning models, including Random Forest and Support Vector Regression, demonstrate the potential to predict post-wildfire stream temperature and turbidity with reasonable accuracy, although uncertainties remain due to the complexity of climate projections and landscape changes. This work underscores the necessity for rigorous, long-term monitoring and the application of sophisticated modeling approaches to better predict and manage the impacts of wildfires on water quality. It emphasizes the importance of incorporating spatial and temporal variability in understanding the direction and magnitude of post-fire impacts. The dissertation contributes valuable insights for developing adaptive management strategies aimed at enhancing the resilience of watersheds and aquatic ecosystems in an era of increasing wildfire activity. By addressing scale-dependent knowledge gaps and recommending future research directions, this research lays the groundwork for more effective water resource management and policy-making in wildfire-prone regions, ultimately aiming to mitigate adverse effects on water quality and support the sustainable use of water resources amidst growing environmental challenges.