Download or read book Estimation of Transport Parameters Using Forced Gradient Tracer Tests in Heterogeneous Aquifers written by and published by . This book was released on 2003 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The evaluation of risk to the environment by subsurface contamination remains one of the major challenges to the Army. Numerical models such as the U.S. Army's Groundwater Modeling System that simulate water flow and chemical transport are increasingly used in remediation design and analysis. This research contributes toward a better understanding of field-testing methods to obtain model parameters. The focus was on both reactive and sorptive parameters. The experimental component of the study was conducted in a three-dimensional, intermediate-scale test tank to obtain accurate data on the behavior of nonreactive and sorptive tracers. This database was used to validate a numerical model, which was then used to analyze behavior over a wider range of scales. A large number of hydraulic and tracer tests were performed in the test aquifer, in three different mean flow configurations: uniform flow, radially divergent flow, and convergent flow. This is a very unique data set that will be available to other researchers. It will help to evaluate models and stochastic theories of up scaled flow and transport. In a related study, a fundamental theoretical analysis of the relationship between surface properties of rock fractures and effective behavior of transport was carried out. The results of both studies are of theoretical and practical significance. This report summarizes the most important results of research in the two areas: intermediate-scale experiments on non-reactive and reactive transport in heterogeneous porous media, and transport with wall reactions in fractures. A list of 18 published papers, conference papers, and papers about to be published is included. (2 refs.).

Download or read book On Single Well Forced Gradient Tracer Tests written by Gareth L. Barns and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Single well forced gradient tracer tests are a potential cost-effective approach to estimate in situ aquifer contaminant fate and transport parameters for use in natural attenuation assessments and remediation schemes. To date dipole flow tracer tests have been used to measure the conservative and hydraulic parameters of an aquifer, while push-pull tests are well characterised for use with biodegrading tracers. The effect of typical aquifer physical heterogeneity on the ability of single well tests to successfully estimate parameters has not yet been characterised. Also, the ability of single well tests to accurately and quickly measure aquifer parameters using tracer mixtures should be analysed. To investigate the effect of physical heterogeneity on single well tests scaled down ultraviolet imaging experiments were performed in a low profile box. Potential tracers for use in mixtures were investigated through column and batch experiments: Inorganic anions and fluorescein, inorganic cations, acetate and trichlorofluoroethene were considered to measure conservative transport parameters, cation exchange capacity, biodegradation potential and hydrophobic sorption respectively. Numerical modelling was used to simulate reactive tracer signals in single well forced gradient tests. Results suggest that dipole flow tracer tests are appropriate for measuring conservative transport parameters and the sorption of lowly retarded tracers, but are not highly suitable for biodegrading tracers. Tests could be performed with non-recirculating flow, allowing simpler modelling, if equal injection and extraction flow rates could be ensured. Push-pull tests are suitable for biodegrading tracers and moderate to highly retarded tracers. This limits the potential to use reactive tracer mixtures in these tests. Dipole flow tracer test breakthrough curves are highly susceptible to heterogeneity, and could be used to identify discrete permeability variations in aquifers. The effect of heterogeneity is not significant on push-pull test breakthrough curves, but seriously affects tracer plume migration. Inorganic anions provided the most reliable conservative tracer. Trichlorofluoroethene was found to be a suitable tracer to measure hydrophobic sorption. The biodegradation surrogate chosen for a field test should biodegrade similarly to the contaminant under study.

Download or read book Effects of Flow Rate Ratios on Tracer Recovery and Transport Parameter Estimation in Forced gradient Tracer Tests written by William Charles Lawrence and published by . This book was released on 1997 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scale Dependence of Transport Parameters Estimated from Forced gradient Tracer Tests in Heterogeneous Formations written by Hsin-Chia Chao and published by . This book was released on 2000 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Calibration and Reliability in Groundwater Modelling written by Karel Kovar and published by . This book was released on 2003 with total page 566 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tools and Analysis of Spatio temporal Dynamics in Heterogeneous Aquifers Applications to Artificial Recharge and Forced gradient Solute Transport written by Daniele Pedretti and published by . This book was released on 2013 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis deals with the development of tools and analysis to characterize and predict artificial recharge and radial convergent solute transport processes in heterogeneous media. The goal is to provide new insights to understand how heterogeneity, which is the main natural source of uncertainty in decision-making processes related with groundwater applications, can be controlled and its effects predicted for practical purposes in these topics. For hydrogeological applications, accurate modeling of phenomena is needed, but it is uncertain. Uncertainty is derived from the spatio-temporal random distribution of hydrodynamic (physical, chemical and biological) variables affecting groundwater processes, which is translated into random distribution of modeling parameters and equations. Such randomness is of two types: epistemic, when it can be reduced increasing the sample frequency of an experiment; aleatory, when it cannot be reduced when more information is analyzed. Sometimes hydrodynamic processes occur at so small scales that they become impossible to characterize with traditional methods, and from a practical perspective, this is analogous to deal with aleatoric model parameters. However, if some constitutive relationship (either empirically, theoretically or physically based) can be built between processes across different scales, then small-scale processes can be reproduced by equivalent large-scale model parameters. Uncertainty becomes amenable to be treated as epistemic randomness, and large-scale characterization techniques can be used to improve the description, interpretation or prediction of these processes. This thesis deals with these topics. The manuscript is composed by two main parts (the first on artificial recharge and the second on solute transport), each of them divided into three chapters. In chapter 1 of each part, a tool is developed to obtain quantitative information to model a selected variable at coarse grid resolutions. In the case of artificial recharge, satellite images are used to model the spatial variability of the infiltration capacity on top soils with a metric-scale detail. In the case of solute transport, a new method to estimate density from particle distribution is shown. In chapters 2, it is explored what processes occurring at the fine scales can affect the interpretation of artificial recharge and solute transport processes at larger scales. In the first part, a combined method that joins satellite images and field data along with a simple clogging model is used to display the equally-possible spatio-temporal mapping of the infiltration capacity of topsoil during artificial pond flooding activities. In the second part, numerical three-dimensional models are used to simulate transport in heterogeneous media under convergent radial flow to a well at fine scale. It is shown that an appropriate model framework can reproduce similar observations on contaminant temporal distribution at controlling section similar to those obtained in the field tracer tests. It is also provided a physical explanation to describe the so-called anomalous late-time behavior on breakthrough curves which is sometimes observed in the reality at larger scales. In the chapters 3, models are used to define the uncertainty around operating parameters in the optic of prediction and management on artificial recharge and solute transport. In the first case, a probability framework is built to define the engineering risk of management of artificial recharge ponds due to random variability of the initial distribution of infiltration, which controls several important clogging factors based on theoretical approaches. In the case of solute transport, it is discussed how equivalent parameters based on mass-transfer models can be related with the geometrical distribution of hydraulic parameters in anisotropic formation, when convergent flow tracer tests are used.

Download or read book Development of experimental monitoring and mathematical methods to quantify water fluxes and transport in heterogeneous aquifer system models written by Marko Hünniger and published by Cuvillier Verlag. This book was released on 2011-08-04 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present study provides experimental and mathematical methods for the understanding and quantification of the water fluxes and solute transport in heterogeneous layered porous groundwater systems characterised by differences in hydraulic conductivities. On the one hand, multi-layered porous groundwater systems with different hydraulic conductivities are characterised by a heterogeneous flow field, which causes a heterogeneous mass transport. On the other hand, extreme differences in hydraulic conductivities create regions of immobile water which influence the mass transport. These two different structural heterogeneities – variable hydraulic conductivities and immobile/stagnant water zones – were investigated experimentally in different laboratory aquifer models. The influence of immobile and stagnant water zones on mass transport was investigated with multi-tracer tests using tracers with different diffusion properties, namely; uranine, bromide, deuterium, oxygen-18 as well as tritium-labelled water, in two-dimensional packed sediment column setups. Two separate column setups were filled. One column setup was filled with clay and sandy material while a second was filled with two different sand sediments. The observed tracer concentration breakthrough curves showed differences in peak concentrations and pronounced tails. Qualitative evaluation of tracer concentration curves led to the assumption that these effects were caused by a diffusive exchange of tracers between immobile and stagnant water regions. The measured data was modelled for the first time in porous media using the Single-Fissure Dispersion Model (SFDM). This model, which was developed for fissured aquifers, yielded a very good fit with all of the tracer concentration curves observed. Further quantitative evaluation of the system parameters (porosities of both materials, diameter of the water¬-bearing layer) in columns consisting of clay and sandy materials produced values that closely matched those independently known. This agreement of parameters confirmed that the model was valid for the heterogeneous systems tested. The model was able to calibrate the tracer curves and to estimate the parameters for the main water-bearing layer for the column consisting of two sandy materials with different hydraulic conductivities. The exchange into the bordering stagnant water occurred via both diffusion and an additional local transport by focusing the flow field into the more conductive material. Thus, in cases where the two materials have rather similar properties, the quantitative evaluation of the parameters of the less permeable layer is only possible when the porosity of that layer is known independently. Both types of experiments with a heterogeneous porous material showed that in groundwater sediments consisting of layers with different hydraulic conductivities the majority of mass is transported in the more conductive layer. The application of the SFDM in porous systems clearly proved that diffusive exchange into regions of immobile or stagnant water is an extremely important factor which has to be quantified. The study clearly demonstrated that multi-tracer experiments modelled with the SFDM are a very useful tool for solving the inverse problem, i.e. for quantifying parameters in such a heterogeneous porous medium. The influence of the local hydraulic conductivity differences on the flow field and mass transport was additionally experimentally investigated in a multi-layered large-scale indoor aquifer model (480 cm x 80 cm x 70 cm). A hydraulically more conductive layer caused a heterogeneous flow field which was traced by an instantaneous injection of uranine, bromide and tritium labelled water. Tracer observations performed in 2-D (vertical) at a high spatial and temporal resolution resulted in single tracer concentration curves. The tracer concentration curves clearly showed that multi-flow-path effects dominated. It was found that these can be adequately analysed using the Multi-Flow Dispersion Model (MFDM). The qualitative analyses showed that the more conductive sediment layer first focused the flow field, and that the water flux split into three different flow paths after leaving the focusing layer, as to be expected. The quantitative evaluation with the MFDM yielded the parameters of these flow paths. The volumetric water fluxes for flow paths with velocities of 2.7 m/d, 1.9 m/d and 1.3 m/d were estimated to be 55 %, 26 % and 19 % of the total water flux, respectively. It was also found that these flow paths were observed only over very short flow distances. After 2.5 m, all water fluxes characterised by different water velocities joined into one water flux which exhibited the mean water velocity but also showed higher dispersivity. This finding is extremely important for the further evaluation of pollutant migration and biodegradation. The present study clearly demonstrated that even in complex groundwater systems with a variety of structural heterogeneities the determination and quantification of different flow paths, and/or mobile and immobile water zones is possible by performing multi-tracer experiments using tracers with different diffusion properties, combined with an adequate modelling approach.

Download or read book Aquifer Characterization Techniques written by Robert G. Maliva and published by Springer. This book was released on 2016-05-26 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents an overview of techniques that are available to characterize sedimentary aquifers. Groundwater flow and solute transport are strongly affected by aquifer heterogeneity. Improved aquifer characterization can allow for a better conceptual understanding of aquifer systems, which can lead to more accurate groundwater models and successful water management solutions, such as contaminant remediation and managed aquifer recharge systems. This book has an applied perspective in that it considers the practicality of techniques for actual groundwater management and development projects in terms of costs, technical resources and expertise required, and investigation time. A discussion of the geological causes, types, and scales of aquifer heterogeneity is first provided. Aquifer characterization methods are then discussed, followed by chapters on data upscaling, groundwater modelling, and geostatistics. This book is a must for every practitioner, graduate student, or researcher dealing with aquifer characterization .

Download or read book Acta Universitatis Carolinae written by and published by . This book was released on 2002 with total page 728 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Estimation of representative groundwater flow and solute transport parameters in heterogeneous formations written by Peter Martin Meier and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Overall Evaluation of the Modelling of the TRUE 1 Tracer Tests written by Paul Marschall and published by . This book was released on 2003 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Handbook of Groundwater Engineering Third Edition written by John H. Cushman and published by CRC Press. This book was released on 2016-11-25 with total page 1726 pages. Available in PDF, EPUB and Kindle. Book excerpt: This new edition adds several new chapters and is thoroughly updated to include data on new topics such as hydraulic fracturing, CO2 sequestration, sustainable groundwater management, and more. Providing a complete treatment of the theory and practice of groundwater engineering, this new handbook also presents a current and detailed review of how to model the flow of water and the transport of contaminants both in the unsaturated and saturated zones, covers the protection of groundwater, and the remediation of contaminated groundwater.

Download or read book Aquifer Test Modeling written by William C. Walton and published by CRC Press. This book was released on 2006-11-15 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recognition of the trend toward using numerical methdos for analyzing aquifer test data, Aquifer Test Modeling delineates the application of numerical Laplace inversion analytical equations and numerical models and demonstrates the use of public domain software. Written by a leading expert with over fifty years of experience, this highly practical text provides a thorough grounding in the terms and methods employed in aquifer test modeling, while also establishing a protocol for organizing and simplifying conceptual model definition and data analysis. Using graphs, tables, and sample datasets to enhance understanding, the author delineates the five major steps involved in the aquifer test modeling process. He discusses the importance of the conceptual model definition as a framework for organizing, simplifying, and idealizing information. The chapters cover the selection of appropriate aquifer test mathematical model equations compatible with previously defined conceptual models and highlight the importance of reviewing the mathematical assumption and the adjustment of data for any departures. They also explain format selection, technique selection, well function or drawdown calculation, and calibration. The book provides five sample data sets to assist the reader in becoming familiar with WTAQ and MODFLOW aquifer test modeling input and output data file contents with confined nonleaky and unconfined aquifer conditions. It includes conceptual models consisting of abbreviated descriptions of aquifer test facilities, aquifer test data, and aquifer parameter values together with selected sample file sets. These are just a few of the features that make the book a valuable tool for estimating the supply and contamination characteristics of aquifers.

Download or read book The Handbook of Groundwater Engineering written by Jacques W. Delleur and published by CRC Press. This book was released on 2010-12-12 with total page 1006 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the increasing demand for adequate water supply caused by the augmenting global population, groundwater production has acquired a new importance. In many areas, surface waters are not available in sufficient quantity or quality. Thus, an increasing demand for groundwater has resulted. However, the residence of time of groundwater can be of the order of thousands of years while surface waters is of the order of days. Therefore, substantially more attention is warranted for transport processes and pollution remediation in groundwater than for surface waters. Similarly, pollution remediation problems in groundwater are generally complex. This excellent, timely resource covers the field of groundwater from an engineering perspective, comprehensively addressing the range of subjects related to subsurface hydrology. It provides a practical treatment of the flow of groundwater, the transport of substances, the construction of wells and well fields, the production of groundwater, and site characterization and remediation of groundwater pollution. No other reference specializes in groundwater engineering to such a broad range of subjects. Its use extends to: The engineer designing a well or well field The engineer designing or operating a landfill facility for municipal or hazardous wastes The hydrogeologist investigating a contaminant plume The engineer examining the remediation of a groundwater pollution problem The engineer or lawyer studying the laws and regulations related to groundwater quality The scientist analyzing the mechanics of solute transport The geohydrologist assessing the regional modeling of aquifers The geophysicist determining the characterization of an aquifer The cartographer mapping aquifer characteristics The practitioner planning a monitoring network

Download or read book Tracer Transport Modeling of the Doublet Well System written by and published by . This book was released on 1994 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Steady-state flow and tracer transport between an injection well and a pumping we in a heterogeneous confined aquifer were investigated with numerical modeling. Calculation of transport was based on the advective model for heterogeneous aquifers. Dispersion was assumed to be controlled by microscale velocity variation. An effective parameter of dispersion evaluated on the breakthrough curves was defined to account for the influences of heterogeneity. Breakthrough curves were calculated by using numerical modeling of transport in a strongly heterogeneous aquifer with spatial heterogeneous transmissivity fields. The results of modeling were processed by comparison with analytical solutions of doublet systems to obtain the effective parameters. A special solution was developed for advective transport in aquifers with a layered structure. Examples of real field heterogeneity were given to show its influence on breakthrough cures and the resulting impact on the effective macroscopic parameters.

Download or read book Selected Water Resources Abstracts written by and published by . This book was released on 1991 with total page 962 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Design and Analysis of Tracer Tests to Determine Effective Porosity and Dispersivity in Fractured Sedimentary Rocks Newark Basin New Jersey written by Glen B. Carleton and published by . This book was released on 1999 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: