Wildfire Effects on Soil Hydrology and Water Quality

Wildfires induce profound alterations to soil structure, surface cover and chemical composition, driving shifts in the hydrological cycle and downstream water quality. Loss of vegetation and organic matter exposes mineral soil to heating, promoting water repellency and reducing infiltration capacity. This transition often results in enhanced surface runoff, increased peak flows and accelerated soil erosion, with attendant mobilization of sediment, nutrients and trace contaminants. Concurrently, ash deposits and burnt organic residues release alkaline compounds, soluble nutrients and metals into soil water, further influencing downstream water bodies. Post-fire landscapes thus exhibit complex interactions between surface‐subsurface water exchange, altered flow pathways and contaminant transport, with implications for flood risk, water supply resilience and ecosystem recovery. Understanding these processes is critical for managing catchments prone to fire and designing mitigation strategies to safeguard water resources at regional and global scales.

Research from Nature Portfolio

Recent studies have highlighted the dynamic interplay between surface and subsurface flow in post‐fire catchments. Field experiments using electrical resistivity and stable water isotopes reveal that following high‐severity burns, rainfall infiltrates into weathered bedrock and persists across seasons, indicating a coupled increase in both runoff and infiltration that sustains higher streamflow peaks and base flows for years after fire. These findings challenge traditional models that assume dominant surface runoff in burned landscapes, emphasising instead a more active surface‐subsurface exchange that shapes vegetation regrowth and landslide susceptibility.

Complementing these insights, analyses of water quality trading frameworks demonstrate the potential of green infrastructure to mitigate post-fire water impairments. By integrating carbon financing with watershed-scale wetland restoration, riparian buffer creation and permeable surface installations, these schemes project substantial savings in electricity and greenhouse gas emissions while generating water quality credits. Such approaches offer pathways to fund nature-based interventions that reduce sediment loads and nutrient fluxes in fire-affected watersheds.

Wildfire Effects on Soil Hydrology and Water Quality publication trend

The graph below shows the total number of articles in wildfire effects on soil hydrology and water quality across all publications each year (not limited to Nature Index journals).

Technical terms

Subsurface exchange: Movement and mixing of water between surface and groundwater stores, influencing flow dynamics and nutrient transport.

Infiltration-excess overland flow: Runoff generated when rainfall intensity exceeds the soil’s capacity to absorb water, leading to surface flow.

Green infrastructure: Nature-based systems such as wetlands, riparian buffers and permeable pavements designed to manage water, enhance biodiversity and sequester carbon.

Water quality trading: Market-based mechanism allowing regulated entities to buy and sell pollution reduction credits to meet water quality targets.

Dissolved organic carbon: Organic molecules in water derived from soil and combustion residues that affect treatment processes and aquatic ecosystem function.

References

1. Importance of subsurface water for hydrological response during storms in a post-wildfire bedrock landscape. Nature Communications (2023).
2. The potential of carbon markets to accelerate green infrastructure based water quality trading. Communications Earth & Environment (2024).
3. Into the unknown: The role of post‐fire soil erosion in the carbon cycle. Global Change Biology (2024).
4. Chemical characteristics of wildfire ash across the globe and their environmental and socio-economic implications. Environment International (2023).
5. Trace Elements in Stormflow, Ash, and Burned Soil following the 2009 Station Fire in Southern California. PLOS ONE (2016).