Megafire affects lateral fluxes and aquatic community: spatiotemporal analysis of a multiscale monitoring network

Authors: Adam Norris*, Brigham Young University, Benjanim W Abbott, Brigham Young University, Ruth Kerry, Brigham Young University
Topics: Water Resources and Hydrology, Environmental Science, Remote Sensing
Keywords: Megafire, remote sensing, spatiotemporal, aquatic community, water quality
Session Type: Virtual Poster
Day: 4/7/2021
Start / End Time: 4:40 PM / 5:55 PM
Room: Virtual 52
Presentation File: Download

A megafire is a wildfire that burns more than 40,500
hectares (100,000 acres) of land. These once rare phenomena are increasing in frequency and
severity in the western U.S. due to climate change. These wildfire regime changes could
threaten essential ecosystem services such as river discharge and nutrient uptake and removal.
Here, we implemented an integrated spatiotemporal monitoring framework to assess water
flow and chemistry conditions following a large megafire in central Utah. We combined high-frequency data from 25 permanent stream water monitoring stations with spatially-extensive
monthly “synoptic” sampling of 85 tributaries, which we compared with remotely sensed
observations of burn severity and weather before and after a megafire. Using a multivariate
analysis, we identified clusters of locations with poor water quality based on temperature,
dissolved oxygen, and turbidity across burn gradients and land-use gradients. As expected, the
megafire caused a large increase in turbidity (~2,000-fold), but this effect was very short-lived,
fading within a year of the disturbance. Conversely, while the megafire caused a small increase
in nutrient concentration and flux, the effects of urban and agricultural land use were much
more pronounced, representing the single most significant control on nutrient dynamics. We
used ground and remotely sensed data to characterize the degree of fire damage and recovery.
We ran a regression analysis to suggest explanations for the changing cluster locations of
different quality standards. We present the high-frequency analysis results and discuss how
changing wildfire regimes could influence aquatic ecosystems and communities throughout the
Intermountain West.

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