A summary of subsurface hydrological and hydrochemical models

Abstract

Numerical simulation in space and time is an established method in fluid flow and solute transport studies. Similarly, the modeling of equilibrium chemistry of aqueous systems has been well developed. Coupling hydrologic transport models and aqueous chemical models is being actively pursued by a number of research groups. To provide a review for researchers as well as field practitioners who may need to select and use models of varying degrees of complexity, summaries of 56 major numerical codes are made in comparative tables with selected references for three broad classes of codes: hydrologic transport models, geochemical models, and hydrochemical models that combine the chemical and transport models. Criteria for code selection and explanations as to how their characteristics were compiled are described. The governing equations for hydrologic flow, solute transport, and chemical relations are briefly described and discussed in light of the assumptions made by the different codes that employ them. Limitations of current modeling conceptualization and practice and areas of present active research effort are noted. Some comments are also given on model validation, a topic of current concern for modeling. Experience in model applications for each code and available information regarding its verification and validation are given in the appendix.

Potassium-calcium exchange in five Ap soils from paddy fields and its effect on potassium concentration in soil solution

“…In numerical simulations involving cation exchange processes in soils, the selectivity coefficient has often been assumed to be constant (Mangold and Tsang 1991). However, as seen from the results obtained in the present study, this assumption is justified only when the load of K-salts is so small that the change in the exchangeable ion composition is negligible.…”

Agricultural Impacts on Groundwater: Processes, Modelling and Decision Support

“…In the representation and simulation of subsurface flow and contaminant transport phenomena and the agricultural processes that affect these phenomena, there are probably as many types of models, modelling philosophies, and ways of classifying models as there are sources and types of groundwater contamination (e.g., Renard et al, 1982;Mangold and Tsang, 1991). For instance in the area of diffuse or nonpoint source pollution in agro-ecosystems, various models have been proposed that deal with different aspects of the plant-soil-climate continuum, some focused more on hydrological aspects, while others consider in more detail plant physiology or the chemistry of soilwater-plant interactions.…”

The potential for criticality following disposal of uranium at low-level waste facilities: Uranium blended with soil

“…Reactive transport modeling has not yet reached the application stage in groundwater modeling. Most of the available codes are considered research codes (van der Heijde and Elnawaway, 1993;National Research Council, 1992;Mangold and Tsang, 1991), which are primarily used by the developers (or someone working closely with developers). Only a handful of examples exist of tkie use of these codes on problems based on real sites.…”