Gordon D. Bennett.

Bio: Gordon D. Bennett. is an academic researcher. The author has contributed to research in topics: Groundwater flow & Groundwater model. The author has an hindex of 4, co-authored 4 publications receiving 823 citations.

Applied contaminant transport modeling

Abstract: Preface. Preface to the First Edition. 1. Introduction. PART 1: CONCEPTS AND TECHNIQUES. 2. Darcy's Law and Advective Transport. 3. Dispersive Transport and Mass Transfer. 4. Transport with Chemical Reactions. 5. Mathematical Model and Analytical Solutions. 6. Simulation of Advective Transport. 7. Simulation of Advective-Dispersive Transport. 8. Simulation of Nonequilibrium Processes and Reactive Transport. PART 2: FIELD APPLICATIONS. 9. A Framework for Model Applications. 10. Building a Contaminant Transport Model. 11. Model Input Parameters. 12. Model Calibration and Sensitivity Analysis. 13. Dealing with Uncertainty. 14. Contaminant Transport Modeling: Case Studies. PART 3: ADVANCED TOPICS. 15. Simulation of Density-Dependent Flow and Transport. 16. Simulation of Flow and Transport in the Vadose Zone. 17. Optimal Management of Groundwater Quality. Appendix A: Darcy's Law and the Variable-Density Flow Equation. Appendix B: Application of Stream Functions to Groundwater Flows. Appendix C: Information on Groundwater Modeling Software. References. Index.

Applied Contaminant Transport Modeling: Theory and Practice

Abstract: This resource is designed to provide clear coverage of the basic principles of solute transport simulation - including the theory behind the most common numerical techniques for solving transport equations and step-by-step guidance on the development and use of field scale models. It presents detailed case histories illustrating how hydrologists, geologists, chemists and environmental engineers apply transport models in real-life situations including landfills, hazardous waste sites and contaminated aquifers.

Analysis of Ground‐Water Remedial Alternatives at a Superfund Site

Abstract: This paper presents a simple yet effective approach and methodology for the problem of evaluating ground-water remedial alternatives at a waste disposal site, and discusses the application of this approach in a case study. The attainment areas, which represent the areas (outside the contaminant source itself) in which remediation is required, are first identified. Simulation of ground-water flow in three dimensions, augmented by fluid particle tracking, is utilized to evaluate the travel times of ground water through the attainment areas. The mixed linear reservoir or “batch flush” model is then used to estimate the number of pore volumes which must be flushed through each attainment area in order to achieve remediation. The travel times are used in conjunction with this pore volume figure to estimate the time required for cleanup under each alternative. By comparing the cleanup time, the costs, and other features of each alternative, a cost-effective remedy for the study site can be determined. While the development of remedial alternatives and the choice of the most cost-effective remedy are highly site-specific, the approach and methodology outlined in this paper have general applicability. The results presented herein also provide insight into the difficulties and special considerations associated with modeling and analyzing remedial alternatives.

Estimating groundwater recharge

Abstract: Understanding groundwater recharge is essential for successful management of water resources and modeling fluid and contaminant transport within the subsurface. This book provides a critical evaluation of the theory and assumptions that underlie methods for estimating rates of groundwater recharge. Detailed explanations of the methods are provided - allowing readers to apply many of the techniques themselves without needing to consult additional references. Numerous practical examples highlight benefits and limitations of each method. Approximately 900 references allow advanced practitioners to pursue additional information on any method. For the first time, theoretical and practical considerations for selecting and applying methods for estimating groundwater recharge are covered in a single volume with uniform presentation. Hydrogeologists, water-resource specialists, civil and agricultural engineers, Earth and environmental scientists and agronomists will benefit from this informative and practical book. It can serve as the primary text for a graduate-level course on groundwater recharge or as an adjunct text for courses on groundwater hydrology or hydrogeology. For the benefit of students and instructors, problem sets of varying difficulty are available at http://wwwbrr.cr.usgs.gov/projects/GW_Unsat/Recharge_Book/

Anthropogenic influences on groundwater arsenic concentrations in Bangladesh

Abstract: The origin of dissolved arsenic in the Ganges Delta has puzzled researchers ever since the report of widespread arsenic poisoning two decades ago. Today, microbially mediated oxidation of organic carbon is thought to drive the geochemical transformations that release arsenic from sediments, but the source of the organic carbon that fuels these processes remains controversial. At a typical site in Bangladesh, where groundwater-irrigated rice fields and constructed ponds are the main sources of groundwater recharge, we combine hydrologic and biogeochemical analyses to trace the origin of contaminated groundwater. Incubation experiments indicate that recharge from ponds contains biologically degradable organic carbon, whereas recharge from rice fields contains mainly recalcitrant organic carbon. Chemical and isotopic indicators as well as groundwater simulations suggest that recharge from ponds carries this degradable organic carbon into the shallow aquifer, and that groundwater flow, drawn by irrigation pumping, transports pond water to the depth where dissolved arsenic concentrations are greatest. Results also indicate that arsenic concentrations are low in groundwater originating from rice fields. Furthermore, solute composition in arsenic-contaminated water is consistent with that predicted using geochemical models of pond-water‐aquifer-sediment interactions. We therefore suggest that the construction of ponds has influenced aquifer biogeochemistry, and that patterns of arsenic contamination in the shallow aquifer result from variations in the source of water, and the complex three-dimensional patterns of groundwater flow.

Towards a comprehensive assessment of model structural adequacy

Abstract: [1] The past decade has seen significant progress in characterizing uncertainty in environmental systems models, through statistical treatment of incomplete knowledge regarding parameters, model structure, and observational data. Attention has now turned to the issue of model structural adequacy (MSA, a term we prefer over model structure “error”). In reviewing philosophical perspectives from the groundwater, unsaturated zone, terrestrial hydrometeorology, and surface water communities about how to model the terrestrial hydrosphere, we identify several areas where different subcommunities can learn from each other. In this paper, we (a) propose a consistent and systematic “unifying conceptual framework” consisting of five formal steps for comprehensive assessment of MSA; (b) discuss the need for a pluralistic definition of adequacy; (c) investigate how MSA has been addressed in the literature; and (d) identify four important issues that require detailed attention—structured model evaluation, diagnosis of epistemic cause, attention to appropriate model complexity, and a multihypothesis approach to inference. We believe that there exists tremendous scope to collectively improve the scientific fidelity of our models and that the proposed framework can help to overcome barriers to communication. By doing so, we can make better progress toward addressing the question “How can we use data to detect, characterize, and resolve model structural inadequacies?”