Saturated Hydraulic Conductivity Measurements in a Loam Soil Covered by Native Vegetation: Spatial and Temporal Variability in the Upper Soil Layer

Saturated hydraulic conductivity (Ks) of soil, especially of the upper soil layer, is a basic parameter for modeling water infiltration and solute transport in the soil. In the present study, spatial and temporal variability of Ks in the upper soil layer of a loam soil, which was covered by native vegetation for 20 years and had not undergone any cultivation treatment, is investigated. Saturated hydraulic conductivity of 76 undisturbed soil samples, taken twice a year at the dry (37 soil samples) and rainy periods (39 soil samples), was measured using a constant head method. The study reveals that Ks values exhibit significant spatial variability over the two time periods of measurement and follow a lognormal distribution with a coefficient of variation greater than 70%. On the contrary, there was no statistically significant seasonal variability of Ks between summer (dry period) and winter (rainy period) sampling (p > 0.05), and, therefore, there was no significant temporal variability of Ks. The outcome of this study indicated that hydrological models have to include more process understanding in terms of natural variability.