Impact of soil surface and subsurface properties on soil saturated hydraulic conductivity in the semi-arid Walnut Gulch Experimental Watershed, Arizona, USA

The estimation of saturated hydraulic conductivity (Ks) is of high relevance to correctly reproduce water fluxes, such as infiltration rates or surface runoff in hydrological simulations. Yet, estimation of Ks is challenging especially in semi-arid regions with particular soil surface characteristics like crusting and sealing. This study presents results of a field campaign in the semi-arid Walnut Gulch Experimental Watershed, Arizona (US), where surface and subsurface Ks measurements were undertaken across the watershed. Data of saturated hydraulic conductivity on crust covered and crust-free surfaces was collected and compared to results of commonly used methods to retrieve spatially distributed Ks data. Results reveal that methods typically used for estimating Ks, such as exponential decay functions or pedo-transfer functions (PTFs), can be inadequate in such regions. The analysis shows that in our study area the presence of surface crust is the dominating factor for determining the spatial distribution of Ks. Furthermore, the results reveal that remote sensing data can provide useful information for estimating surface Ks values as it could be successfully applied for the spatial detection of surface crust characteristics.