Hydrological Response of Natural Mediterranean Watersheds to Forest Fires

Konstantinos X. Soulis,Christos Theodoropoulos,Konstantina Amalia Generali,Emmanouil Psomiadis,Christina Papadaki

doi:10.3390/hydrology8010015

Konstantinos X. Soulis, Christos Theodoropoulos + Show 3 more

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https://doi.org/10.3390/hydrology8010015

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Abstract

Fires are common in forested Mediterranean-climate watersheds. Forest fires cause abrupt land use/cover (LULC) changes affecting soil properties and hydrological processes within and across watersheds. A major forest fire in Attica, Greece, that affected the Lykorrema stream experimental watershed provided the opportunity for an in-depth study of the impact of forest fires on the hydrological balance of natural Mediterranean watersheds. To this end, detailed hydrometeorological data recorded for five years before and for five years after the fire incidence were utilized. SWAT model was also used to consider the potential influence of meteorological conditions temporal variability on the results of the analysis. Specifically, SWAT model was parameterized calibrated and validated for the pre-fire and the post-fire conditions using the corresponding detailed hydrometeorological data for the respective periods. Then the two versions of the model were applied for the entire period providing comprehensive time series for all the flows and storages in the studied watershed. In this way, the post-fire LULC and soil properties changes were the only influencing factors driving the alterations in the hydrological balance allowing an impartial comparison. The obtained results highlighted the considerable impact of forest fires on the watersheds’ hydrological functioning. Specifically, the maximum direct runoff depths and the maximum flow rates were substantially higher in the post-fire conditions. In contrast, actual evapotranspiration was reduced, when the effect of fire was considered. The obtained results indicate that the altered post-fire LULC and soil properties are major drivers of the watershed’s hydrological balance changes. SWAT model performed sufficiently well for both the pre- and post-fire conditions and provided a deeper insight into the impact of forest fires on the hydrological functioning of natural Mediterranean watersheds.

Highlights

One of the most common hazards of the forested watersheds in the Mediterranean basin is forest fires
The initial model performance indicated that, at least in this application, soil water assessment tool (SWAT) model is unable to describe the hydrological response of the watershed for both scenarios without calibration even if detailed soil, land covet, topographic and field data were used for its set-up
Detailed hydro-meteorological data for an adequate period before and after a wildfire incident in a well-studied watershed are valuable for the investigation of the effect of forest fires

Summary

Introduction

One of the most common hazards of the forested watersheds in the Mediterranean basin is forest fires. Anthropogenic activities are considered as a driving force of wildfires, the lack of forest monitoring and climate change play a significant role [1,2,3]. In 2018 the Intergovernmental Panel on Climate Change (IPCC) reported that humaninduced warming has already increased to 1 ◦ C above pre-industrial levels. Alterations in vegetation cover, soil properties disturbance, changes in the hydrological behavior of watersheds as well as probable life and property loss are some of the results of a forest fire [5]. Loss in vegetation cover has a direct impact in the hydrological response of a watershed with increased overland

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