Spatial variability of saturated hydraulic conductivity in shallow macroporous soils in a forested basin

Field (single-ring infiltrometer) and laboratory (constant head permeameter) measurements of saturated hydraulic conductivity (K-H) were used in combination to examine macropore effects on K-H in shallow forest soils in a small basin in southern Ontario, Canada. Soil matrix K-H generally decreased with depth for hillslope podzols and stream valley gleysols. Differences in average maximum and minimum matrix K-H were observed between soil types, with lowest values occurring in the valley gleysols. Bulk profile K-H (assumed to include the effects of macropores) had no apparent spatial pattern within a given soil type, and mean bulk K-H did not differ between soil types. K-H Of macroporous soil was similar to matrix hydraulic conductivities for the porous hillslope podzols; however, it could be several orders-of-magnitude greater than the minimum matrix K-H observed at a given site for the gleysols. This difference increased with total profile thickness. Geostatistical analyses revealed anisotropic distributions of both bulk and matrix K-H in the basin, with the maximum and minimum directions of spatial correlation being parallel and normal to the stream valley, respectively. Degree of anisotropy and scale of spatial dependence were lower for bulk K-H relative to the minimum matrix K-H values. (C) 1997 Elsevier Science B.V.