Comment on A Modular Framework for Modeling Unsaturated Soil Hydraulic Properties Over the Full Moisture Range by Weber et al. COMMENT

Weber et al. (2019) (W19 in the following) present a modular framework for parametrizing soil hydraulic properties. The W19 model framework is almost identical to the model system developed jointly by Peters (2013), https://doi.org/10.1002/wrcr.20548, Iden and Durner (2014), https://doi. org/10.1002/2014wr015937, and Peters (2014), https://doi.org/10.1002/2014wr016107, to which we will refer as PDI (Peters-Durner-Iden) model in the following. The primary goal of this comment is to uncover some inconsistencies of the W19 formulation. In the following, we (i) comment on the statement made by W19 regarding the number of parameters in the original PDI formulation, (ii) critically analyze the use of their function to parameterize the water retention curve (WRC), and (iii) show that, in contrast to the statement in W19, using their formulation of for parametrizing noncapillary hydraulic conductivity leads to systematic deviations from the physically based film-conductivity model developed by Tokunaga (2009), https://doi.org/10.1029/2009wr007734.

Automated summary

The commentary critically analyzes the framework proposed by Weber et al. (2019) for parameterizing soil hydraulic properties, highlighting inconsistencies in their formulation, especially in terms of the number of parameters and the approach to parameterize the water retention curve and noncapillary hydraulic conductivity.