Characterizing surface soil layer saturated hydraulic conductivity in a Mediterranean natural watershed

Saturated hydraulic conductivity (K-s ) is a key parameter in hydrology, although obtaining representative K-s values especially in natural watersheds is challenging due to its variability in space and time and the difficulties in field measurements. In this study, the challenges and limitations in characterizing the surface soil layer K-s in a Mediterranean natural watershed are presented, based on the analysis of long-term field data and of detailed hydrological data covering a 14-year period (2005-2018). The obtained results indicate a generally high spatial variability at all scales, while there seems to be a dominance of small-scale variability, which complicates the determination of representative K-s values characterizing the watershed. The temporal variability was less profound; however, temporal stability of K-s seems to be a significant issue after major disturbances such as wildfires. The results highlight the challenges and limitations in the setup and parameterization of hydrological models, especially in ungauged watersheds.