Development of one-dimensional solutions for water infiltration. Analysis and parameters estimation

- Two infiltration solutions, computationally efficient, are proposed.
- The solutions were tested with Hydrus-1D code, for different soil types.
- We proposed van Genuchten-Mualem parameters for the NRCS intake families.
- The solution was able to assess the effect of initial water content on infiltration.

SummaryThe design of an irrigation system requires proper understanding of the infiltration process. Two original approximate solutions were developed in this study in order to determine one-dimensional vertical infiltration and profile water distribution.The Boltzmann transformation was used to solve the Richards equation. The accuracy of the solutions was verified by comparing results obtained with Hydrus-1D simulations. The solutions were also compared with the US Department of Agriculture-Natural Resources and Conservation Service (USDA-NRCS) intake families for infiltrated depths between 2 and 16 cm, using soils from Carsel and Parrish database.Simulations results of both solutions were in close agreement with Hydrus-1D. For all the cases studied, the corresponding root mean square error (RMSE) values were up to 0.56 cm, with coefficients of correlation (R2) larger than 0.99.Therefore, The comparison shows inexact matching, with acceptable correspondence, between simulated soils and NRCS curve numbers, The procedure developed to fit the USDA-NRCS intake families with the proposed solutions leads to characterize each family by the van Genuchten-Mualem parameters, and an initial soil water content. Furthermore, results suggests to consider initial water content in fine-textured soils. In the case of intake families, initial water content began to affect in Family 0.5 and became very decisive in the Family 0.05.Additionally, the proposed method, which are applicable to any descriptor of unsaturated hydraulic properties, have practical application, including accurate determination of the sorptivity of a soil at various water contents, and requires low computational effort.

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