Simple consistent models for water retention and hydraulic conductivity in the complete moisture range

Abstract

[1] The commonly used hydraulic models only account for capillary water retention and conductivity. Adsorptive water retention and film conductivity is neglected. This leads to erroneous description of hydraulic properties in the dry range. The few existing models, which account for film conductivity and adsorptive retention are either difficult to use or physically inconsistent. A new set of empirical hydraulic models for an effective description of water dynamics from full saturation to complete dryness is introduced. The models allow a clear partitioning between capillary and adsorptive water retention as well as between capillary and film conductivity. The number of adjustable parameters for the new retention model is not increased compared to the commonly used models, whereas only one extra parameter for quantifying the contribution of film conductivity is required for the new conductivity model. Both models are mathematically simple and thus easy to use in simulation studies. The new liquid conductivity model is coupled with an existing vapor conductivity model to describe conductivity in the complete moisture range. The new models were successfully applied to literature data, which all reach the dry to very dry range and cannot be well described with the classic capillary models. The investigated soils range from pure sands to clay loams. A simulation study with steady-state water transport scenarios shows that neglecting either film or vapor conductivity or both can lead to significant underestimation of water transport at low water contents.

A pore-size classification for peat bogs derived from unsaturated hydraulic properties

“…The model is physically more comprehensive in that it ensures zero water content at oven dryness, and accounts for water flow in completely filled capillaries, partly filled capillaries, adsorbed water films, and isothermal vapour diffusion. We used the parameterization derived by Peters (2013), in the modified form published by Iden and Durner (2014), and Peters (2014). The PDI retention curve model has an identical number of free parameters as the VGM.…”

“…The WRC of the PDI model family (Peters, 2013(Peters, , 2014Iden and Durner, 2014) is given by the equation…”

Column-scale unsaturated hydraulic conductivity estimates in coarse-textured homogeneous and layered soils derived under steady-state evaporation from a water table

“…This process can be modeled with the Buckingham-Darcy law considering both liquid and vapor flow contributions to the unsaturated hydraulic conductivity (Peters, 2013):…”

“…Based on the numerically simulated pressure head profile shown in Fig. 1 as well as results of Peters and Durner (2010) and Peters (2013), the pressure head at DF (h max ) is realized as a critical value at which liquid and vapor conductivity curves meet each other (i.e., K l (h max ) = K v (h max )). Below h max , liquid water flow dominates transport and above h max vapor flow is dominant.…”

A Modified van Genuchten-Mualem Model of Hydraulic Conductivity in Korean Residual Soils

“…The samples belong to each group due to the presence of some fine-grained soil and residual formation environments. The low values of the tortuosity factor can be related to adsorptive water retention and film conductivity [20,21], which is beyond the scope of this study. For each group, the relative hydraulic conductivity, K r , for the modified VGM model was first compared with that of the VGM model and subsequently with the measured value.…”