Abstract
In the last few years, many studies have been published by authors from several countries offering approximations and use of the inverse method. However, the unique environmental conditions and distinct properties of the tropical soils in Brazil require extra considerations and the need to adjust these methods to tropical soil conditions. Considering the above, this determined the parameters of the van Genuchten (1980) model (θs, θr, α, n) of the water retention curve in the soils. It also determined the parameter (Ks) of the soil’s hydraulic conductivity curve by solving an inverse problem using the HYDRUS-2D model, considering cumulative infiltration data collected in the field by means of an infiltration test using the tension infiltrometer. It then compared the hydraulic properties determined by these methods in relation to the standard laboratory method. The inverse method was able to efficiently determine the water retention curves in the soils here studied; however, it was not possible to reliably determine the unsaturated hydraulic conductivity curve.
Highlights
The technological advance observed in recent times at the computational level has allowed development, with greater use and improvement of increasingly sophisticated and demanding mathematical models of flow and/or water balance and transport of solutes in soil
The curves θ (h) presented in Figure 2, determined by the inverse modeling of the objective functions Φ(Q, θi, θf, θ100kPa, θ1500kPa), built with the infiltration data and initial and final water contents in soil and soil moisture at 100 kPa and 1500 kPa, resulted in good agreement when compared to the points determined in laboratory
The comparison between the retention curves reveals that, in general, for low soil water tensions of less than 1 cm.c.a, there is a similarity in soil moisture between the curves estimated in the laboratory and those obtained by the Hydrus-2D software
Summary
The technological advance observed in recent times at the computational level has allowed development, with greater use and improvement of increasingly sophisticated and demanding mathematical models of flow and/or water balance and transport of solutes in soil. These models are generally based on the numerical resolution of the Richards equation which, because it contains two unknowns (θ and h) in a single equation, requires previous knowledge of the hydrodynamic characteristics of the soil for its solution. Analyzing the data numerically generated for an experiment, the authors have concluded that the cumulative infiltration curve alone does not contain enough information to provide a unique inverse solution. Additional information on the flow process, such as soil moisture and matric potentials measured at one or more locations in the soil profile is required to achieve successful unique inverse solutions to soil hydraulic functions
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