A TWENTY-YEAR EVALUATION OF THE RESPONSE OF COASTAL WATER QUALITY TO WILDFIRES IN CALIFORNIA

Wildfires have a significant impact on a wide range of environmental variables and can lead to punctuated change in terrestrial and aquatic ecosystems. For example, ash and aerosols mix with seawater and interact with incoming solar radiation. Terrestrial detritus and leached solutes from burned catchments can be transported to coastal waters via discharge from rivers, runoff, or debris flows after storms. While impacts of wildfires on rivers and lakes are well studied, their impacts on coastal and marine environments have recently emerged as a key area of investigation in part because of the catastrophic coastal wildfires in California and elsewhere.

This project draws on numerous large-scale geospatial datasets for wildfires and ecological variables in California coastal zones to build a big data platform that can be used to resolve complex spatiotemporal interactions between wildfires and coastal habitats. Wildfire perimeters, precipitation model outputs, land use, topography, coastal catchments, water quality parameters (e.g., fecal indicator bacteria concentrations), and other environmental factors are broken into daily increments spanning January 1^st, 2003, to December 31^st, 2022. Qualities of the catchments and cumulative modeled precipitation over both recently burned and unburned regions are linked to water quality parameters near coastal zones.

This platform enables identification of spatiotemporal relationships between wildfires, catchments, and coastal conditions that lead to anomalous responses in coastal water quality parameters. This approach establishes well-defined, multiannual baselines, and compares coastal water quality across multiple catchments of similar and different size, land use, topography, fire history, climate, and more. In contrast to traditional studies that focus on the consequences of individual fires, this platform seeks to identify the general mechanisms by which wildfires in coastal catchments influence nearby seawater quality and ecology along the California coast. This talk will present an overview of the data structures, visualization techniques, geospatial time series extraction, and specific results for how fecal indicator bacteria in coastal waters respond to storms following wildfires.