2026-09-29 パシフィック・ノースウェスト国立研究所（PNNL）
Wildfires influence how materials from the land surface are transported into rivers. Crossing key burn area thresholds leads to large increases in how much material is carried downriver. Top: Snowmelt for a river not affected by wildfire. Bottom: Snowmelt for a wildfire-affected river. (Image courtesy of Jake Cavaiani | Pacific Northwest National Laboratory)
＜関連情報＞
- https://www.pnnl.gov/publications/thresholds-wildfire-impacts-river-chemistry-depend-hydrology
- https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025WR040678
河川系はいつ「火災の影響」を受けるのか？火災の範囲と深刻度が生物地球化学的流出に対する水文学的制御をどのように変化させるかをシミュレーションする When Do Riverine Systems “Feel the Burn”? Simulating How Burn Extent and Severity Modulate Hydrologic Controls on Biogeochemical Export
K. A. Wampler, A. N. Myers-Pigg, H. Kang, P. Regier, T. D. Scheibe, K. D. Bladon
Water Resources Research Published: 30 January 2026
DOI:https://doi.org/10.1029/2025WR040678
Abstract
Wildfires impact terrestrial landscapes and downstream river corridors through shifts in vegetation and soil properties leading to downstream hydrologic and water quality impacts. The magnitude of these impacts depend on a complex and interconnected set of wildfire, landscape, and aquatic processes. Here, we isolate the impact of post-fire hydrologic changes on streamflow, nitrate, and dissolved organic carbon using the Soil and Water Assessment Tool (SWAT) model. We explore how responses differ across burn severity and area burned in two test basins: a humid forested basin and a semi-arid mixed land use basin. We ran 1830 wildfire simulations testing impacts of area burned, burn severity, and post-fire precipitation on streamflow, nitrate, and dissolved organic carbon. Our work suggests that area burned thresholds differ with burn severity and analyte. Additionally, post-fire transport of dissolved organic carbon was sensitive to both area burned and severity, while nitrate was primarily sensitive to area burned. Despite a muted (−9.5 to 5.7 mm yr−1 change) hydrologic response in the semi-arid basin, the model predicted large (7%–288% increase) shifts in dissolved organic carbon, suggesting that post-fire shifts in flow pathways and soil properties are key in its response. The limited shifts in nitrate responses in the simulations highlight that terrestrial post-fire transformations, rather than hydrologic changes, may control the increases in stream nitrate often observed post-fire. As wildfire regimes are shifting, improving understanding of post-fire nutrient export responses is critical to protect freshwater resources and aquatic ecosystems.
