Interpretation of field tracer tests of a single fracture using a transient solute storage model

Raven, Kenneth G.; Novakowski, Kent; Lapcevic, P. A.

doi:10.1029/wr024i012p02019

Cited by 119 publications

(75 citation statements)

References 45 publications

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“…A number of field tracer tests were conducted in fractured rock in the 1970s and 1980s [e.g., Webster et al, 1970;Grove and Beetem, 1971;Kreft et al, 1974;Claassen and Cordes, 1975;Gustafsson and Klockars, 1981;Tester et al, 1982;Black and Kipp, 1983;McCable et al, 1983;Cullen et al, 1985;Garnier et al, 1985;Novakowski et al, 1985;Raven et al, 1988;Shapiro and Nicholas, 19891. These tests were conducted to estimate rock properties (e.g., fracture porosity and dispersivity) for groundwater flow and transport in fractured media for (1) nuclear waste disposal Davison et al, 1982;Novakowski et al, 1985;Raven et al, 19881, (2) aquifer water resources [e.g., Black and Kipp, 19831, (3) geothermal reservoir production [e.g., Tester et al, 1982;Home and Rodriguez, 1983;McCable et al, 19831, and others.…”

Section: Field Tracer Tests and Observationsmentioning

confidence: 99%

“…Many field tracer tests have been conducted in fractured rock since 1970 [e.g., Webster et al, 1970;Gamier et al, 1985;Raven et al, 1988;Cucas et al, 1990b;Gustafsson and Andersson, 1991;Hademzann and Heer, 1996;Becker and Shapiro, 2000;Reimus et al, 2003a, b]. A few long-term, large-scale contaminant transport events have also been observed in fractured rock systems [e.g., Bibby, 1981;Rudolph et al, 1991;Shapiro, 20011.…”

Section: Introductionmentioning

confidence: 99%

“…Maloszewski & Zuber, 1985 Hodgkinson & Lever, Gustafsson &Anderson, 1991Gamier et al, 1985Maloszewski & Zuber, 1990Moench, 1995Novakowski et al, 1985Raven et al, 1988Maloszewski & Zuber, 1993 …”

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confidence: 99%

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Field-scale effective matrix diffusion coefficient for fractured rock: Results from literature survey

Zhou

Liu

Molz

et al. 2007

Journal of Contaminant Hydrology

103

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Matrix diffusion is an important mechanism for solute transport in fractured rock.We recently conducted a literature survey on the effective matrix diffusion coefficient, D i , a key parameter for describing matrix diffusion processes at the field scale. Forty field tracer tests at 15 fractured geologic sites were surveyed and selected for the study, based on data availability and quality. Field-scale D: values were calculated, either directly using data reported in the literature or by reanalyzing the corresponding field tracer tests. Surveyed data indicate that the effective-matrix-diffusion-coefficient factor FD (defined as the ratio of D i to the lab-scale matrix diffusion coefficient [ Dm 3 of the same tracer) is generally larger than one, indicating that the effective matrix diffusion coefficient in the field is comparatively larger than the matrix diffusion coefficient at the rock-core scale. This larger value can be attributed to the many mass-transfer processes at different scales in naturally heterogeneous, fractured rock systems. Furthermore, we observed a moderate trend toward systematic increase in the FD value with observation scale, indicating that the effective matrix diffusion coefficient is likely to be statistically scale dependent. The FD value ranges from 1 to 10,000 for observation scales from 5 to 2,000 m. At a given scale, the F ' value varies by two orders of magnitude, reflecting the influence of differing degrees of fractured rock heterogeneity at different sites. In addition, the surveyed data indicate that field-scale longitudinal dispersivity generally increases with observation scale, which is consistent with previous studies. The scaledependent field-scale matrix diffusion coefficient (and dispersivity) may have significant 1 implications for assessing long-term, large-scale radionuclide and contaminant transport events in fractured rock, both for nuclear waste disposal and contaminant remediation.

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Section: Field Tracer Tests and Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Field-scale effective matrix diffusion coefficient for fractured rock: Results from literature survey

Zhou

Liu

Molz

et al. 2007

Journal of Contaminant Hydrology

103

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“…The common theme was to develop different process models for understanding the physics of flow and transport in the subsurface and use these characterized sites for validating the model conceptualizations and mathematical formulation. Another set of studies focused on calibrating and validating different mathematical models using tracer test results in fractured aquifers (e.g., Zuber, 1992, 1993;Cacas et al, 1990a, b;Raven et al, 1988;Shapiro and Nicholas, 1989). The scope of these validation studies was to determine whether the values of the model-fitted parameters agreed with those known from independent determinations.…”

Section: Introductionmentioning

confidence: 99%

A Validation Process for the Groundwater Flow and Transport Model of the Faultless Nuclear Test at Central Nevada Test Area

Hassan¹

2003

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EXECUTIVE SUMMARYMany sites of groundwater contamination rely heavily on complex numerical models of flow and transport to develop closure plans. This has created a need for tools and approaches that can be used to build confidence in model predictions and make it apparent to regulators, policy makers, and the public that these models are sufficient for decision making. This confidence building is a long-term iterative process and it is this process that should be termed "model validation." Model validation is a process not an end result. That is, the process of model validation cannot always assure acceptable prediction or quality of the model. Rather, it provides safeguard against faulty models or inadequately developed and tested models. Therefore, development of a systematic approach for evaluating and validating subsurface predictive models and guiding field activities for data collection and long-term monitoring is strongly needed. This report presents a review of model validation studies that pertain to groundwater flow and transport modeling. Definitions, literature debates, previously proposed validation strategies, and conferences and symposia that focused on subsurface model validation are reviewed and discussed. The review is general in nature, but the focus of the discussion is on site-specific, predictive groundwater models that are used for making decisions regarding remediation activities and site closure. An attempt is made to compile most of the published studies on groundwater model validation and assemble what has been proposed or used for validating subsurface models. The aim is to provide a reasonable starting point to aid the development of the validation plan for the groundwater flow and transport model of the Faultless nuclear test conducted at the Central Nevada Test Area (CNTA).The review of previous studies on model validation shows that there does not exist a set of specific procedures and tests that can be easily adapted and applied to determine the validity of site-specific groundwater models. This is true for both deterministic and stochastic models, with the latter posing a more difficult and challenging problem when it comes to validation. This report then proposes a general validation approach for the CNTA model, which addresses some of the important issues recognized in previous validation studies, conferences, and symposia as crucial to the process. The proposed approach links model building, model calibration, model predictions, data collection, model evaluations, and model validation in an iterative loop. The approach focuses on use of collected validation data to reduce model uncertainty and narrow the range of possible outcomes of stochastic numerical models. It accounts for the stochastic nature of the numerical CNTA model, which used Monte Carlo simulation approach. The proposed methodology relies on the premise that absolute validity is not even a theoretical possibility and is not a regulatory requirement. Rather, it highlights the importance of testing as many aspect...

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“…Others have attributed the tailing to the diffusion of mass into stagnant zones along the fracture wall (Raven et al 1988), or into low flow regions associated with smallaperture spaces within the fracture channel (Abelin et al 1991;Kunstmann et al 1997). …”

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confidence: 99%

Models of tracer breakthrough and permeability in simple fractured porous media

Johnston

Atkinson

Odling

et al. 2005

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Tailing and bimodal behaviour of tracer breakthrough curves from tracer tests conducted in fractured porous media are commonly presented as 'deviations' from the Fickian model for homogeneous porous media. Tailing is mainly attributed to: (1) tracer storage brought about by diffusion between mobile and static regions of fluid; (2) a concentration of flow towards the wider (aperture) and, thus, more permeable fracture zones; and (3) the high variance in fracture conductivity and consequent mixing of tracer. Bi-(or multi-) modality has been attributed to solute following a few highly permeable flow paths. Systematic numerical simulations of flow and transport in geometrically simple fractured porous media were conducted using a 2D finite difference flow code and a particle tracking transport model. As a simplification only advective dispersion was considered. The modelling study produced a large variety of tracer breakthrough curves, including two patterns commonly seen in field data -the backward tailed uni-modal type and the Gaussian type. The study demonstrates that different types of breakthrough might be characteristic of particular sets of conceptual models for heterogeneities and, as such, may provide a useful pointer in the application and interpretation of tracer tests.

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Interpretation of field tracer tests of a single fracture using a transient solute storage model

Cited by 119 publications

References 45 publications

Field-scale effective matrix diffusion coefficient for fractured rock: Results from literature survey

Field-scale effective matrix diffusion coefficient for fractured rock: Results from literature survey

A Validation Process for the Groundwater Flow and Transport Model of the Faultless Nuclear Test at Central Nevada Test Area

Models of tracer breakthrough and permeability in simple fractured porous media

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