A review of wildfire impacts on stream temperature and turbidity across scales

Abstract

Wildfire has increased in severity and frequency with climate change and human activities in recent years, threatening water-related ecosystem services. Forested watersheds are at risk of impacts of wildfires that alter land cover, and hydrological processes, and influence drinking water quality and aquatic habitat. To date, most research on post-fire hydrologic effects has focused on water quantity, while stream temperature and turbidity received less attention. In this study, we reviewed 62 articles to examine wildfire drivers and processes associated with turbidity and stream temperature behavior through a geographic lens in the context of ecosystem services. Our goals were to (1) evaluate drivers of post-fire changes in turbidity and stream temperature; (2) examine mechanisms and processes responsible for spatial and temporal variabilities of changes; and (3) address scale-dependent knowledge gaps to recommend future research directions. Positive correlations between turbidity changes following wildfire were heavily influenced by fire severity, forest diversity, and landscape alterations by human activities such as salvage logging. Stream temperature increases result from loss of riparian canopy cover and decreased shading, but they were highly site-specific and dependent on topographic variations. We attribute variabilities in our findings to climate variability and heavy disparity across spatial and temporal scales when assessing the direction and magnitude of post-fire impacts. Future research should incorporate more long-term rigorous monitoring efforts and spatiotemporally explicit models to better represent the complex post-fire hydrologic system that influences water quality.