Analysis of single-ring infiltrometer data for soil hydraulic properties estimation: Comparison of BEST and Wu methods

Knowledge of soil hydraulic properties is important for modeling hydrological processes and related contaminant transport. This study compared four methods in analyzing single-ring infiltrometer data to estimate the saturated hydraulic conductivity (Ks) and the water retention parameter (α). These were: (1) original BEST (Beerkan Estimates of Soil Transfer Parameters through Infiltration Experiments, Lassabatere et al., 2006) method, defined as BEST_slope; (2) a modified BEST method, defined as BEST_intercept (Yilmaz et al., 2010); (3) Wu1 (Wu et al., 1999) which attempts the best fit of a generalized solution to the infiltration curve using the whole infiltration curve; and (4) Wu2 (Wu et al., 1999) which is suitable for the steady state flow case. The first three methods are suitable for the transient flow state. The infiltration data of 54 different cases within four soil texture classes (sand, sandy loam, medium loam, and clay loam) were used. The results suggest that the modified version (BEST_intercept) has a better performance (more reasonable estimates) than the original (BEST_slope). Both the BEST_slope and BEST_intercept methods perform poorly for the sandy soils. The Wu1 method performs better in fitting the experimental infiltration curve, and produces more cases with reasonable values (normally positive values) of Ks and α than both the BEST_slope and BEST_intercept. In order to apply these existing methods to wider conditions (e.g., sandy soils, wet soils, basic oxygen furnace slag), the inversion estimation algorithms and the experimental operations in the field require further improvement.