Hydrological impacts of wildfires on a global scale: An analysis based on the fire-enabled models of ISIMIP.

Wildfires can significantly alter the hydrological regime of a watershed until vegetation is reestablished and the hydrological cycle returns to its pre-disturbance state. These wildfire-induced changes can disrupt flow patterns by reducing rainfall interception and evapotranspiration due to vegetation loss. Additionally, wildfires can affect soil permeability, either through ash deposition or, in boreal regions, by facilitating permafrost thaw.

Land surface models play a critical role in understanding and predicting interactions between the Earth's surface the atmosphere. They enable detailed assessments of water, energy, and carbon cycling, which are essential for climate modeling, ecosystem management, and policy development.

In this study, we analyze surface runoff simulated by six fire-enabled ISIMIP3a land surface models for the period 1850–2019. We identify changes in the runoff coefficient between the most fire-active and least fire-active decades in the timeseries. To isolate the role of long-term climatic trends, we utilize counterfactual simulation outputs driven by detrended observational climate data, where the signal of global warming has been removed.

Our preliminary results reveal consistent patterns between the modeled results and observed runoff changes reported in other studies, though substantial variability exists among the different land surface models. This work aims to assess the ability of state-of-the-art land surface models to represent a complex interaction on the land surface, while also enhancing our understanding of the hydrological impacts of wildfires and contributing to improving the representation of fire-hydrology processes in modeling frameworks.

This work is supported by Leverhulme Centre for Wildfires, Environment, and Society through the Leverhulme Trust, grant number RC-2018-023.