16-4 A review and synthesis of surface and subsurface streamflow generation processes following wildfire disturbance

Session: Wildland Fire: An Agent of Geomorphic, Ecologic, and Societal Change

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Authors:

Abstract:

Wildfires are increasing in frequency, size, and severity in portions of the western United States (US). Water quality and quantity can be negatively affected by wildfire, potentially endangering critical water supply watersheds. Regional variability in the directionality and magnitude of post-wildfire shifts in streamflow generation increases uncertainty in estimates of wildfire effects on water supplies. Prior reviews have focused more on streamflow generation by overland flow following a wildfire. We review and synthesize wildfire effects on hydrologic processes and the resulting changes in streamflow generation mechanisms with broader inclusion of subsurface streamflow generation processes. A conceptual model summary of wildfire effects on streamflow generation emphasizes: (1) strength of seasonality and synchrony of precipitation and potential evapotranspiration, (2) net shifts in interception, evaporation, and transpiration relative to total annual precipitation, (3) vegetation changes, including compensatory uptake and type conversion, (4) degree of overlap in rainfall rates and infiltration, (5) fire extent and severity, (6) burn scar positioning (e.g., in headwaters or proximal to watershed outlet), (7) scale-dependent groundwater leakage, (8) near-surface water storage reduction, and (9) soil to groundwater connectivity. Major gaps and challenges include lack of pre-fire data in addition to isolating wildfire effects from influences of climatic variability, water withdrawals, post-fire land management, and compound and overlapping disturbances. Notable future opportunities are ongoing advances in gridded and remotely sensed precipitation and fire-effects data; linking geophysical, isotopic tracer, and geochemical signatures to diagnose hydrologic changes; continuing physically based and data-driven model advancements; and analysis of streamflow generation recovery trajectories across diverse watersheds.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7324

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