Assessment of evaluation methods using infiltration data measured in heterogeneous mountain soils

• Differences in the parameter and fitting quality of 7 equations were revealed.
• For most of the cases, all of these equations exhibited good quality of fitting.
• Kutílek-Krejča, Green-Ampt, and Philip Eqs. displayed poor fitting in a few cases.
• Significantly different mean Ks estimates and also mean S estimates were noted.
• Swartzendruber and Brutsaert Eqs. exhibited good consistency with the reference Ks.

In order to obtain infiltration parameters and analytical expressions of the cumulative infiltration and infiltration rate, raw infiltration data are often evaluated using various infiltration equations. Knowledge about the evaluation variability of these equations in the specific case of extremely heterogeneous soils provides important information for many hydrological and engineering applications. This paper evaluates five well-established physically-based equations (Eqs.) - Brutsaert (1977), Green and Ampt (1911), Kutílek and Krejča (1987), Philip (1957), Swartzendruber (1987) -, and two empirical Eqs. - Horton (1940), Mezencev (1948) using measured infiltration data. This paper also compares sorptivity (S) and saturated hydraulic conductivity (Ks) estimates of these Eqs. with the reference estimates using early-time parts resp. quasi-steady parts of raw data. A total of 47 single ring infiltration experiments (datasets measured on three different sites of hydrologically important mountain podzols) were evaluated using the seven Eqs. and also using the methods for reference estimates of S and Ks. From the quality-of-fit perspective, all of the seven Eqs. characterized large part of the datasets properly. In some cases, Philip, Kutílek and Krejča, and Green and Ampt Eqs. led to poor fits of the datasets (measured mostly on site 3 characterized by the lowest thicknesses of the organic horizon, and a more bleached eluvial horizon than on the other tested sites). For the parameters evaluated on site 3, 1) the mean S estimates of Green and Ampt, Kutílek and Krejča, and Philip were significantly lower than the mean S estimates of Brutsaert and Swartzendruber, and 2) the mean Ks estimates of Kutílek and Krejča, and of Philip, were significantly lower than the mean Ks estimates of Brutsaert, Swartzendruber and Horton. The Swartzendruber and Brutsaert Eqs. exhibited 1) high quality of fitting and 2) good consistency of the Ks estimates with reference values.