Effect of Soil Properties on Hydraulic Conductivity‐Moisture Relationships

A field study was initiated to examine relationships between in situ hydraulic conductivity, soil‐water suction, and soil physical and chemical properties. Data from the study were used to describe relationships between soil properties and slopes of hydraulic conductivity‐soil water suction curves, i.e., In K vs. In S curve slopes ( N ). Soil particle size distribution and soil moisture desorption slopes were also evaluated. Sand to silt ratio (SA/SI), geometric mean particle diameter (GMD), and an index of geometric mean standard deviation (GMSD) were strongly related to slope of the In K vs. In S curves. These same parameters were also functionally related to observed differences between slopes of In K vs. In S curves and slopes of soil moisture desorption curves. Particle statistical indices and sand to silt ratio (SA/SI) were better predictors of curve slopes than were particle size percentages alone. An attempt was made to determine any correlations between K ( S ) and these soil properties and to estimate K ( S ), using selected soil physical properties. Using “best fit” predictive models, estimated K ( S ) values varied from measured values by a factor of 2 to 3 at the 60% confidence interval and by a factor of 7 to 12 at the 95% confidence interval.