IDENTIFYING RELATIONS BETWEEN SPATIAL AND WATER QUALITY VARIABLES IN WILDFIRE BASINS ACROSS THE WESTERN US

Wildfires can result in loss of land cover, alteration and erosion of soils, and changes to water quantity and quality, resulting in challenges for resource managers. The U.S. Geological Survey is conducting an interdisciplinary study to better understand the critical drivers of post-wildfire effects in several basins located in California, Oregon, Montana, Colorado, and New Mexico. Water-quality in 12 USGS wildfire-affected basins varies by geographical and climatological regions leaving gaps in the understanding regarding the critical drivers of post-wildfire water quality. In each basin, water-quality data was collected throughout the first few year(s) post wildfire when water quality is typically most affected. Remote sensing data was leveraged to assist with addressing critical needs for geospatial prediction of impacts on water quality and quantity. Additionally, a conceptual framework was used to identify how categorical “Drivers” affect quantifiable water-quality variables (Factors, Stressors and Effects). Using factors (i.e., watershed characteristics) identified from the conceptual framework and discrete water-quality data, Principal Component Analyses (PCA) were conducted for each basin to determine which explanatory variables were more likely to be associated with post-wildfire water quality. We used two techniques to analyze the data: spatial PCA on the watershed characteristics and PCA on the water-quality data. Using factor analysis in conjunction with each study basin’s PCA provided insight to the correlation between the water-quality variables and the watershed factors as it relates to post wildfire water quality. Information gained from this analysis can inform future efforts focused on predicting post-wildfire effects on water supplies in similar geographical regions.