Scaling relationships between saturated hydraulic conductivity and soil physical properties

Saturated hydraulic conductivity (K-s) is an important soil hydraulic property that affects water flow and the transport of dissolved solutes. Obtaining sufficient and reliable K, data for large-scale process modeling is always a challenge due to the extremely high spatial variability. The objectives of this study were (i) to determine if a monofractal or multifractal approach is needed to describe the variability in K, and its soil surrogates, and (ii) to identify which soil property best reflects the spatial distribution of K, across a wider range of scales. Saturated hydraulic conductivity and soil physical property data were collected from a 384-m transect, located at Smeaton, SK, Canada. Observation scale variability and relationships were examined using statistical and geostatistical methods. Statistical scale-invariance was evaluated through the Hurst scaling parameter (H). Multiple scale variability and relationships were studied using multifractal and joint multifractal techniques. Results indicate that for all the studied variables 0.80 < H < 0.90, suggesting a certain degree of statistical scale-invariance and long-range dependency. At the observation scale, the variability in K-s was significantly related to sand (SA) and silt (SI) distribution (R = 0.40 for SA and -0.39 for SI, P < 0.01; n = 128), whereas, across a wider range of scales, the variability in K, was related only to clay (CL) and organic C (OC). The result indicates scale dependent relationships between K-s and soil physical properties, which implies that the success of predictive models such as pedotransfer functions (PTFs) and K-s aggregation techniques depends largely on the correspondence between observation and implementation scales.