Apparent dispersion in transient groundwater flow

Goode, Daniel J.; Konikow, Leonard F.

doi:10.1029/wr026i010p02339

Cited by 102 publications

(72 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The scale dependence of dispersivity is generally believed to result from spatial and temporal variations in the ground-water velocity field, which are caused by both spatial variations in hydraulic conductivity, and spatial and temporal variations in hydraulic gradient (Goode and Konikow 1990). Aquifer heterogeneity results in additional plume dispersion, beyond that seen in the laboratory, because the solute moves at different rates through different parts of the aquifer.…”

Section: Dispersivitymentioning

confidence: 99%

“…Aquifer heterogeneity results in additional plume dispersion, beyond that seen in the laboratory, because the solute moves at different rates through different parts of the aquifer. Temporal variations in hydraulic gradient have been shown to have a strong effect on transverse dispersion (Goode and Konikow 1990;Rehfeldt and Gelhar 1992;van der Kamp et al 1994). …”

Section: Dispersivitymentioning

confidence: 99%

See 1 more Smart Citation

Development of a three-dimensional ground-water model of the Hanford Site unconfined aquifer system: FY 1995 status report

Wurstner¹,

Thorne²,

Chamness³

et al. 1995

115

View full text Add to dashboard Cite

DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document. Executive SummaryA three-dimensional ground-water flow model has been developed for the uppermost unconfined aquifer at the Hanford Site in south-central Washington. This model is being developed to support the Hanford Site Ground-Water Surveillance Project objectives of 1) identifying and quantifying existing, emerging, or potential ground-water quality problems, and 2) assessing the potential for contaminants to migrate from the Hanford Site through the groundwater pathway.The approach to develop the three-dimensional model was to 1) refine the conceptual hydrogeologic model, 2) calibrate a two-dimensional version of the model with an inverse calibration method, and 3) develop the three-dimensional model based on all available information.The model is based on the Coupled Fluid, Energy, and Solute Transport (CFEST) code; however, the database of geologic and hydrologic information is constructed so that the conceptual model can be implemented in codes other than CFEST.The model consists of 10 hydrogeologic layers. Layers 1 through 9 correspond to the hydrogeologic units comprising the unconfined aquifer system. Layer 10 corresponds to basalt. The conceptual model was developed using the ground surface as the top of the model. The numerical model uses only the saturated portion of the sediments below the ground surface (i.e., the unconfined aquifer). Hydraulic conductivities were assigned to layers based on data from aquifer pumping tests, slug tests, and some laboratory tests. Some layers were assigned a constant value of hydraulic conductivity, while others were zoned with different hydraulic conductivities being assigned to each zone. The goal of the three-dimensional model calibration was to preserve the total transmissivity calculated by the two-dimensional inverse calibration, while honoring data available for hydrogeologic layers.The model grid consists of 821 surface nodes and 721 surface elements. The placement of nodes in the grid was selected so that 1) sources would be represented as closely as possible by nodes, 2) potential contours and gradients could be resolved, and 3) geologic layer extents and other important three-dimensional hydrogeologic aspects of the problem could be represented as accurately as possible. Boundary and source conditions used in the model are similar to previous ... lu efforts at the Site. A natural areal recharge distribution was included to reflect infiltration and recharge to the unconfined aquifer.Steady-state predictions from the three-dimensional model for the 1979 calibration period compared well with the observed water table. There is close agreement in most areas of the Site. The three-dimensional model is ready for routine application in steady-state, and we are proceeding with the construction of transport models for tritium, iodine-129, and nitrate based on the flow model.In addition to the three-dimensional model dev...

show abstract

Section: Dispersivitymentioning

confidence: 99%

Section: Dispersivitymentioning

confidence: 99%

Development of a three-dimensional ground-water model of the Hanford Site unconfined aquifer system: FY 1995 status report

Wurstner¹,

Thorne²,

Chamness³

et al. 1995

115

View full text Add to dashboard Cite

show abstract

“…Several researchers Goode and Konikow, 1990;Dagan et al, 1996) identified slowly varying, unsteady, uniform flow characterized by variation in the direction of the hydraulic gradient as a possible explanation for the observed transverse macrodispersivities being larger than predicted by the steady-state theory. This mechanism allows the plume to slowly shift from side to side.…”

Section: -14mentioning

confidence: 99%

The Role of Dispersion in Radionuclide Transport - Data and Modeling Requirements: Revision No. 1

Venture¹

2004

View full text Add to dashboard Cite

“…For example, Sugita and Gillham (1995a,b) present a conceptual model that indicates a nonideal reactive breakthrough (i.e., greater spreading and tailing) greater than predictable by the classical advectivedispersion equation with pore scale variations in retardation factor. Goode and Konikow (1990) illustrate that uncertainty in transient flow behavior gives rise to a greater apparent dispersivity. Tritscher et al (2000) illustrate that neglecting unsaturated zone effects leads to a local specific yield strongly influenced by water table depth and mildly dependent on recharge rate.…”

Section: Process Identification Simplification and Representationmentioning

confidence: 99%

Uncertainty Analysis Framework - Hanford Site-Wide Groundwater Flow and Transport Model

Cole¹,

Bergeron²,

Murray³

et al. 2001

View full text Add to dashboard Cite

SummaryAt the request of the U.S. Department of Energy (DOE), Pacific Northwest National Laboratory (PNNL) embarked on a new initiative to strengthen the technical defensibility of the Hanford site-wide groundwater model (SGM) used to make groundwater flow and transport predictions at the U.S. Department of Energy's Hanford Site in southeastern Washington State (Figure 1.1). The initial focus of the initiative is the characterization of major uncertainties in the current conceptual model that would affect model predictions. The long-term goals of the initiative are the development and implementation of a stochastic uncertainty estimation methodology in future assessments and analyses using the site-wide groundwater model. This report focuses on the development and implementation of the uncertainty analysis framework. The overall technical approach for this framework will closely follow the recommendations of the SGM external peer review panel made in 1999 (Gorelick et al. 1999). As suggested by the panel, the framework being developed acknowledges the inherent uncertainty in conceptual model representations and associated model inputs and thus in any predictions. This new framework acknowledges that prescribed processes, physical features, initial and boundary conditions, system stresses, field data, and model parameter values are not known and cannot be known with certainty and, as a result, predictions of heads and concentrations in three dimensions over time will be uncertain as well. The approach will specifically address those areas of special interest that were identified by the expert panel. These include uncertainty related to• alternative model structures and constructs of processes (e.g., different zonation, different boundary conditions, large-scale features, stresses, and chemical reactions)• model parameters• model scale and resolution issues.This report represents one of the first steps in development of this new SGM uncertainty framework by• identifying the types of assessments for which the SGM will likely be applied (Section 2)• discussing the various sources of uncertainty and the issues associated with the assessment of uncertainty as they relate to the development of this new framework for assessment of uncertainty in the Hanford SGM predictions. The sources of uncertainty include the most common high-level categories: uncertainty resulting from natural variability, model structure, and model parameters (Section 3).• providing a detailed description of the current conceptual model of the Hanford Site unconfined aquifer system that includes an assessment of the uncertainties and issues associated with that model (Section 4), the well picks used in the current interpretation of the hydrostratigraphic structure (Appendix A), and the results of a literature search that developed an initial bibliography and iii assessment regarding the various potential intercommunication mechanisms between the unconfined aquifer system and the uppermost confined aquifer system in the underlying basalts (Appendix ...

show abstract

Apparent dispersion in transient groundwater flow

Cited by 102 publications

References 7 publications

Development of a three-dimensional ground-water model of the Hanford Site unconfined aquifer system: FY 1995 status report

Development of a three-dimensional ground-water model of the Hanford Site unconfined aquifer system: FY 1995 status report

The Role of Dispersion in Radionuclide Transport - Data and Modeling Requirements: Revision No. 1

Uncertainty Analysis Framework - Hanford Site-Wide Groundwater Flow and Transport Model

Contact Info

Product

Resources

About