Efficient calculation of solute transport in heterogeneous soils exhibiting non-Richards-type unsaturated flow

• Published in: Journal of environmental quality 1999-03, Vol.28 (2), p.493-497
• Main Authors: Rooij, Gerrit H., Vries, Peter
• Format: Article
• Language: English
• Subjects: Bodemfysica; bodemoplossing; Earth sciences; Earth, ocean, space; Exact sciences and technology; Hydrogeology; Hydrology. Hydrogeology; infiltratie; infiltration; ruimtelijke variatie; Soil Physics; soil solution; Soils; Solute transport; spatial variation; Surficial geology; Unsaturated flow
• ISSN: 0047-2425; 1537-2537
• DOI: 10.2134/jeq1999.00472425002800020014x

Soil heterogeneity hampers our ability to calculate field-scale solute leaching. Many of the existing field-scale modeling attempts are laborious, time consuming, and computationally demanding. Non-Richards-type flows (e.g., fingering) cannot be handled by methods based solely on the heterogeneity of the soil hydraulic properties. We developed a time- and cost-effective approach that starts with a plot-scale solute transport model that must incorporate any special flow features in the field of interest. The field was modeled as an ensemble of plot-scale columns with random properties. The computational demand was reduced by: (i) simplifying the plot-scale model; (ii) keeping only the most influential parameters stochastic; (iii) replacing a full Monte Carlo simulation by systematic parameter sampling; and (iv) trans-forming the model output for one column to that of another where possible. The method was demonstrated for a field exhibiting fingered flow in the topsoil. A recently developed model to calculate solute leaching from a single finger served as the column-scale model. Three parameters appeared to be key for solute leaching to the groundwater. For two of them, the breakthrough curve for one value of the parameter could be transformed to approximate the curve for all other values. Consequently, field-scale solute leaching could be computed with