Effect of fire induced water repellency on soil hydraulic properties and water flow

摘要

Water infiltration into the root zone, its retention in soil and drainage from the soil profile, are highly sensitive to the presence, degree and persistence of soil water repellency (SWR). Prolonged drought periods and wildfires can increase SWR substantially, thus the aim of this study was to determine the effect of forest fire-induced water repellency on soil hydraulic properties, infiltration and water flow in unsaturated soil (vadose) zone. Infiltration experiments with water and ethanol were conducted on forest sites, selected according to their exposure to fire: heavily burned (A), burned (B) and non-affected as the control site (C). Infiltration data were used as an input for inverse determination of soil hydraulic parameters required for computer model calibration (HYDRUS 2D/3D). Then, a one-year climatic scenario for 2016 with measured meteorological data was simulated using HYDRUS-1D software. Data showed that in the case of soil exposure to high temperatures (forest fires), a relatively large increase of SWR is observed. Compared to the control plot, a considerably greater difference between the hydraulic conductivity, Ks, values for water and ethanol was found at both fire affected plots. This suggested positive relationship between soil water repellency and reduced water infiltration. Numerical simulation of the intensive (extreme) rainfall event clearly showed that SWR affects soil water balance by reducing the infiltration and increasing the surface runoff.