Hydrological impacts of a wildfire in a Boreal region: The Västmanland fire 2014 (Sweden)

Abstract

The largest forest wildfire in Swedish modern history burnt 14,000 ha of Boreal forest in the Västmanland County (south-central Sweden) during the summer of 2014. Here, we assess the impacts of this wildfire on the hydrological regime during the three years after it happened. In the empirical experiment carried out, four catchments (two burnt and two non-burnt nearby) with similar character and climate and with mean area of 20 km2 were compared. A total of 23 descriptors accounting for climate, land cover and flow signatures were defined and evaluated before and after the wildfire, using both remote sensing products and in situ streamflow observations. The results show three main changes in the hydrological behaviour of the burnt areas: (i) variation in duration and timing of snow season, with shorter and later beginning of the season; (ii) more dynamic behaviour of the streamflow, with smaller variation coefficient, a reduction in duration of high and low flows conditions and a more oscillating pattern; and, (iii) variations in catchment response (flashiness, runoff coefficient and actual evapotranspiration) from rainfall-events mainly during summer, but also in late autumn The study also reflects the usefulness of the combined analysis of flow signatures and remote sensing products to detect changes in catchment hydrology.