The impacts of forest fires on watershed hydrological response. A review

Forest fires pose significant environmental challenges globally, profoundly affecting watershed hydrology. As human activities increase and climate change exacerbates, the incidence and severity of forest fires have escalated, leading to profound modifications in watershed hydrological behavior. This review synthesizes findings from numerous studies conducted between 1966 and May 2024, focusing on the short- and long-term effects of forest fires on watershed runoff, peak flow, sediment transport, and water quality. Key findings include significant increases in runoff volume and peak flow, with post-fire runoff in some regions increasing by up to 500 %. Fires also alter soil properties, reducing infiltration and increasing erosion. These changes persist over time, impacting groundwater recharge, baseflow, and water quality. Elevated levels of phosphorus, nitrate, and other pollutants in post-fire runoff present risks to aquatic ecosystems and human health, with potential for eutrophication and contamination of drinking water. The study highlights regional differences in hydrological responses to forest fires, with Mediterranean regions experiencing rapid runoff increases, while boreal forests exhibit more gradual hydrological changes. This review also discusses the methodologies employed, including hydrological models and remote sensing technologies, and outlines future research needs to address gaps in our understanding of fire-watershed interactions. Improved management strategies are essential to mitigate the hydrological impacts of increasing fire activity in forested regions worldwide.