Alternative α* Parameter Estimation for Simplified Beerkan Infiltration Method to Assess Soil Saturated Hydraulic Conductivity

In situ characterization of the saturated hydraulic conductivity (K-s) requires a large number of experiments, sampling, and laboratory measurements that are time-consuming and expensive. Simplified Beerkan Infiltration (SBI) method was developed to estimate an approximate K-s based on the infiltration curve without any sampling procedures. For that purpose, alpha* parameter, which is used in the calculation of K-s, was commonly set to a fixed value based on soil texture. This approach was not sufficient for an accurate K-s estimation. For a relatively dry soil, a new approach involving an empirical structural parameter was proposed to calculate an approximation of the alpha* parameter based on the shape of the steady state asymptote of the Beerkan cumulative infiltration. The new alpha* parameter was tested on simplified Beerkan infiltration (SBI) method in over 32 Beerkan experiments selected from the Soil World Infiltration Global (SWIG) database. The steady state SBI (SSBI) method estimated K-s with an accuracy close to those estimated with the BEST (Beerkan Estimation Soil Transfer) method. The R-2 correlation factor for the SSBI method in K-s estimation with BEST intercept and steady methods were 0.982 and 0.994, respectively. For the transient SBI method, the R-2 correlation factors calculated with BEST methods were lower; 0.858 and 0.827, respectively. Therefore, the application of the new alpha* parameter to the steady state simplified Beerkan approach allows an easy, inexpensive way to estimate accurately K-s.