Abstract
Abstract. Sorptivity is a parameter of primary importance in the study of unsaturated flow in soils. This hydraulic parameter is required to model water infiltration into vertical soil profiles. Sorptivity can be directly estimated from the soil hydraulic functions (water retention and hydraulic conductivity curves), using the integral formulation of Parlange (1975). However, calculating sorptivity in this manner requires the prior determination of the soil hydraulic diffusivity and its numerical integration between initial and final saturation degrees, which may be difficult in some situations (e.g., coarse soil with diffusivity functions that are quasi-infinite close to saturation). In this paper, we present a procedure to compute sorptivity using a scaling parameter, cp, that corresponds to the sorptivity of a unit soil (i.e., unit values for all parameters and zero residual water content) that is utterly dry at the initial state and saturated at the final state. The cp parameter was computed numerically and analytically for five hydraulic models: delta (i.e., Green and Ampt), Brooks and Corey, van Genuchten–Mualem, van Genuchten–Burdine, and Kosugi. Based on the results, we proposed brand new analytical expressions for some of the models and validated previous formulations for the other models. We also tabulated the output values so that they can easily be used to determine the actual sorptivity value for any case. At the same time, our numerical results showed that the relation between cp and the hydraulic shape parameters strongly depends on the chosen model. These results highlight the need for careful selection of the proper model for the description of the water retention and hydraulic conductivity functions when estimating sorptivity.
Highlights
Soil sorptivity represents the capacity of a soil to absorb or desorb liquid by capillarity and is one of the key factors for modeling water infiltration into soil (Cook and Minasny, 2011)
The theory section details the scaling procedure that relates the square sorptivity to the (i) square scaled sorptivity, SK∗2(−∞, 0), which we show is equal to the parameter cp, and (ii) the product of scale parameters and correcting factors accounting for the contribution of initial water contents
The other models have inflection points positioned at larger abscissas, with similar intermediate values for the Brooks and Corey (BC) and the van Genuchten–Burdine (vGB) models and the largest abscissas for the van Genuchten–Mualem (vGM) model (Fig. 1a)
Summary
Soil sorptivity represents the capacity of a soil to absorb or desorb liquid by capillarity and is one of the key factors for modeling water infiltration into soil (Cook and Minasny, 2011). (6)– (10) under the boundary conditions of a slightly positive water pressure head at surface and relatively dry initial conditions We focus on these conditions since they constitute the most common experimental conditions for most water infiltration experiments and related procedures for characterizing soil hydraulic properties (Angulo-Jaramillo et al, 2016). The square scaled sorptivity corresponds to the sorptivity of a unit soil (unit value for all the scale parameters, except the residual water content fixed at zero) and for the whole range of water pressure heads, i.e., It depends only on the soil hydraulic shape parameters, and its determination features the main algebraic complexity of the whole scaling procedure; the rest relies on simple algebraic operations (multiplication and sums). We show how the tabulated values of the square scaled sorptivity cp can be used to upscale sorptivity and provide the sorptivity corresponding to a zero water pressure head at the surface for relatively small initial water contents
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
