SPATIAL VARIABILITY OF SATURATED HYDRAULIC CONDUCTIVITY IN SHALLOW MACROPOROUS SOILS IN A FORESTED BASIN

Field (single-ring infiltrometer) and laboratory (constant head permea meter) measurements of saturated hydraulic conductivity (K-H) were use d 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 g enerally decreased with depth for hillslope podzols and stream valley gleysols. Differences in average maximum and minimum matrix K-H were o bserved between soil types, with lowest values occurring in the valley gleysols. Bulk profile K-H (assumed to include the effects of macropo res) had no apparent spatial pattern within a given soil type, and mea n bulk K-H did not differ between soil types. K-H Of macroporous soil was similar to matrix hydraulic conductivities for the porous hillslop e podzols; however, it could be several orders-of-magnitude greater th an the minimum matrix K-H observed at a given site for the gleysols. T his 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 cor relation being parallel and normal to the stream valley, respectively. Degree of anisotropy and scale of spatial dependence were lower for b ulk K-H relative to the minimum matrix K-H values. (C) 1997 Elsevier S cience B.V.