Lateral saturated hydraulic conductivity of soil horizons evaluated in large-volume soil monoliths

Evaluating the lateral saturated hydraulic conductivity, Ks,l, of soil horizons is crucial for understanding and modelling the subsurface flow dynamics in many shallow hill soils. A Ks,lmeasurement method should be able to catch the effects of soil heterogeneities governing hydrological processes at the scale of interest, in order to yield Ks,lrepresentative values over large spatial scales. This study aims to develop a field technique to determine spatially representative Ks,lvalues of soil horizons of an experimental hillslope. Drainage experiments were performed on soil monoliths of about 0.12 m3volume, encased in situ with polyurethane foam. Median Ks,lof 2450 mm·h-1and 552 mm·h-1were estimated in the A and B horizon, respectively. In the upper part of the B horizon, the median Ks,lwas 490 mm·h-1, whereas it mostly halved near the underlying restricting layer. The decline of Ks,lvalues with depth was consistent with the water-table dynamics observed at the same site in previous studies. Moreover, the Ks,lfrom the monoliths were in line with large spatial-scale Ks,lvalues reported from the hillslope in a prior investigation based on drain data analysis. This indicated that the large-scale hydrological effects of the macropore network were well represented in the investigated soil blocks. Our findings suggest that performing drainage experiments on large-volume monoliths is a promising method for characterizing lateral conductivities over large spatial scales. This information could improve our understanding of hydrological processes and can be used to parameterize runoff-generation models at hillslope and catchment scale.