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

Abstract: In situ characterization of the saturated hydraulic conductivity (Ks) 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 Ks based on the infiltration curve without any sampling procedures. For that purpose, α* parameter, which is used in the calculation of Ks, was commonly set to a fixed value based on soil texture. This approach was not sufficient for an accurate Ks estimation. For a relatively dry soil, a new approach involving an empirical structural parameter was proposed to calculate an approximation of the α* parameter based on the shape of the steady state asymptote of the Beerkan cumulative infiltration. The new α* 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 Ks with an accuracy close to those estimated with the BEST (Beerkan Estimation Soil Transfer) method. The R2 correlation factor for the SSBI method in Ks estimation with BEST intercept and steady methods were 0.982 and 0.994, respectively. For the transient SBI method, the R2 correlation factors calculated with BEST methods were lower; 0.858 and 0.827, respectively. Therefore, the application of the new α* parameter to the steady state simplified Beerkan approach allows an easy, inexpensive way to estimate accurately Ks.