Linking Fire-induced Evapotranspiration Shifts to Streamflow Signals in the Western United States
Abstract
The impact of wildfire on water availability is a critical issue in the western United States (US). The direction, magnitude, and duration of fire-induced evapotranspiration (ET) shifts are of particular import because ET and precipitation are the two largest components of local and regional water budgets. Further, ET is highly sensitive to disturbances that alter vegetation and infiltration rates. Prior work shows that the effects of fire on soil moisture availability, the surface energy balance, and actual ET amounts are variable. Controlling relationships between ET response and landscape attributes are spatially dynamic, making it difficult to predict the effect of fire on streamflow. This study aims to explicitly link post-fire ET shifts to streamflow signals and other water partitioning processes. Ten USGS-gaged basins with burns exceeding 5% of their total drainage area in a single water year are selected from the western US. For each basin, 30-meter (m) actual ET (ETa) data, generated with the United States Geological Surveys Simplified Surface Energy Balance algorithm, are overlain with static and dynamic landscape and climatic variables resampled at the same resolution. The pixel-level differences of pre and post-fire ETa and evaporation to precipitation ratios (ETa/P) are quantified and relationships between ETa/P shifts and landscape attributes are explored with k-means clustering and non-linear random forest models. Stream gaging data are independently analyzed to detect post-fire shifts in baseflow and peak flow metrics. Where annual ETa and streamflow shifts align in magnitude and direction, causal relationships between ETa and streamflow shifts are evaluated with panel regression or wavelet coherence analysis; critical disturbance thresholds required to elicit streamflow signals are defined. Watershed storage, vegetation and soil dynamics, and the seasonality of post-fire ETa and ETa/P response are further evaluated where streamflow shifts do not align. The study findings suggest that some major western US river basins are more susceptible to post-fire water supply changes than others due to the location-specific influence of fire and climate on ETa and watershed recovery.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.H54H..08C