Parsing Weather Variability and Wildfire Effects on the Post‐Fire Changes in Daily Stream Flows: A Quantile‐Based Statistical Approach and Its Application. Issue 10 (13th October 2021)

• Record Type: Journal Article
• Authors: Beyene, Mussie T.; Leibowitz, Scott G.; Pennino, Michael J.
• Is Part Of: Water resources research. Volume 57:Issue 10(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-10-13
• Subjects: wildfires -- Western United States -- low and peak flows -- post‐fire weather -- bootstrap method -- double mass analysis -- quantile regression; Hydrology -- Periodicals; 333.91
• DOI: 10.1029/2020WR028029
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: Determining wildland fire impacts on streamflow can be problematic as the hydrology in burned watersheds is influenced by post‐fire weather conditions. This study presents a quantile‐based analytical framework for assessing fire impacts on low and peak daily flow magnitudes, while accounting for post‐fire weather influences. This framework entails (a) the bootstrap method to compute the relative change in the post‐fire annual flow and weather statistics, (b) double mass analysis to detect if post‐fire baseflow and quick‐flow yield ratios are significantly altered, and (c) a quantile regression method to parse fire effects on flow at a specific quantile. We illustrate the applicability of this analytical framework using 44 western US streams with at least 5% of their watershed area burned. Results indicate that large, high‐severity burns in upland watersheds can raise the streamflow magnitude at the 0. 05 t h and 0. 95 t h quantiles for at least the five post‐fire years. Quantile regression results show that the median fire‐related increase in flow for the five post‐fire years can be up to 5, 000% (Standard Error; S . E . < 2%) at the 0. 05 t h quantile and 161% ( S . E . < 10%) at the 0. 95 t h quantile. The fire‐related increase in flow was often pronounced at the 0. 05 t h quantile for streams in the Pacific Northwest and California regions. The difference in fire effects on flow (at both quantiles) across streams was related to post‐fire weather, pyrology, physiography, and land cover. The proposed analytical framework can be useful for detecting and quantifying fire effects on the low and peak stream flows in burned watersheds without overlapping disturbances. Key Points: Evaluating the impact of watershed burning on streamflow can be problematic due to the confounding effect of post‐fire weather influences A quantile‐based analytical framework is presented for assessing fire effect on low & peak flow while accounting for weather influences This analytical framework can be useful for inferring fire effect on low & peak flows in burned watersheds without overlapping disturbances