Elucidation of Flow and Transport Processes in a Variably Saturated System of Interlayered Sediment and Fractured Rock Using Tracer Tests

We present new random walk methods to solve flow and transport problems in saturated/unsaturated porous media, including coupled flow and transport processes in soils, heterogeneous systems modeled through random hydraulic conductivity and recharge fields, processes at the field and regional scales. The numerical schemes are based on global random walk algorithms (GRW) which approximate the solution by moving large numbers of computational particles on regular lattices according to specific random walk rules. To cope with the nonlinearity and the degeneracy of the Richards equation and of the coupled system, we implemented the GRW algorithms by employing linearization techniques similar to the L-scheme developed in finite element/volume approaches. The resulting GRW L-schemes converge with the number of iterations and provide numerical solutions that are first-order accurate in time and second-order in space. A remarkable property of the flow and transport GRW solutions is that they are practically free of numerical diffusion. The GRW solvers are validated by comparisons with mixed finite element and finite volume solvers in one- and two-dimensional benchmark problems. They include Richards' equation fully coupled with the advection-diffusion-reaction equation and capture the transition from unsaturated to saturated flow regimes. &#160;For completeness, we also consider decoupled flow and transport model problems for saturated aquifers.

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Characterization of hydraulic properties in the upper vadose zone for two aquifers in Slovenia

10.5194/egusphere-egu21-2407 ◽

2021 ◽

Author(s):

Vesna Zupanc ◽

Matjaž Glavan ◽

Miha Curk ◽

Urša Pečan ◽

Michael Stockinger ◽

...

Keyword(s):

Stable Isotopes ◽

Soil Water ◽

Water Flow ◽

Vadose Zone ◽

Hydraulic Properties ◽

Isotope Composition ◽

Transport Processes ◽

Precipitation Event ◽

Water Fluxes ◽

Flow And Transport

Environmental tracers, present in the environment and provided by nature, provide integrative information about both water flow and transport. For studying water flow and solute transport, the hydrogen and oxygen isotopes are of special interest, as their ratios provide a tracer signal with every precipitation event and are seasonally distributed. In order to follow the seasonal distribution of stable isotopes in the soil water and use this information for identifying hydrological processes and hydraulic properties, soil was sampled three times in three profiles, two on Kr&#353;ko polje aquifer in SE Slovenia and one on Ljubljansko polje in central Slovenia. Isotope composition of soil water was measured with the water-vapor-equilibration method. Based on the isotope composition of soil water integrative information about water flow and transport processes with time and depth below ground were assessed. Porewater isotopes were in similar range as precipitation for all three profiles. &#160;Variable isotope ratios in the upper 60 cm for the different sampling times indicated dynamic water fluxes in this upper part of the vadose zone. Results also showed more evaporation at one sampling location, Brege. The information from stable isotopes will be of importance for further analyzing the water fluxes in the vadose zone of the study sties.&#160; This research was financed by the ARRS BIAT 20-21-32 and IAEA CRP 1.50.18 Multiple isotope fingerprints to identify sources and transport of agro-contaminants. &#160;

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Inferring saline tracer transport characteristics from time-lapse GPR experiments

10.5194/egusphere-egu21-7541 ◽

2021 ◽

Author(s):

Peter-Lasse Giertzuch ◽

Alexis Shakas ◽

Bernard Brixel ◽

Joseph Doetsch ◽

Mohammadreza Jalali ◽

...

Keyword(s):

Electrical Conductivity ◽

Velocity Field ◽

Nuclear Waste ◽

Time Lapse ◽

Transport Processes ◽

Nuclear Waste Repository ◽

Tracer Transport ◽

Tracer Injection ◽

Flow And Transport ◽

Conductivity Sensor

Monitoring and characterization of flow and transport processes in the subsurface has been a key focus of hydrogeological research for several decades. Such processes can be relevant for numerous applications, such as hydrocarbon and geothermal reservoir characterization and monitoring, risk assessment of soil contaminants, or nuclear waste disposal strategies.Monitoring of flow and transport processes in the subsurface is often challenging, as they are usually not directly observable. Here, we present an approach to monitor saline tracer migration through a weakly fractured crystalline rock mass by means of Ground Penetrating Radar (GPR), and we evaluate the data quantitatively in terms of a flow velocity field and localized difference GPR breakthrough curves (DRBTC).Two comparable and repeated tracer injection experiments were performed within saturated rock on the decameter scale. Time-lapse single-hole reflection data were acquired from two different boreholes during these experiments using unshielded and omnidirectional borehole antennas. The individual surveys were analyzed by difference imaging techniques, which allowed ultimately for tracer breakthrough monitoring at different locations in the subsurface. By combining the two complimentary GPR data sets, the 3D tracer velocity field could be reconstructed.Our DRBTCs agree well with measured BTCs of the saline tracer at different electrical conductivity monitoring positions. Additionally, we were able to calculate a DRBTC for a location not previously monitored with borehole sensors. The reconstructed velocity field is in good agreement with previous studies on dye tracer data at the same research locations. Furthermore, we were able to resolve separate flow paths towards different monitoring locations, which could not be inferred from the electrical conductivity sensor data alone. The GPR data thus helped to disentangle the complex flow field through the fractured rock.Out technique can be adapted to other use cases such as 3D monitoring of fluid migration (and thus permeability enhancement) during hydraulic stimulation and tracing fluid contaminants &#8211; e.g. for nuclear waste repository monitoring.

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Flow and Transport Through Unsaturated Fractured Rock--Second Edition.

Vadose Zone Journal ◽

10.2113/1.1.201 ◽

2002 ◽

Vol 1 (1) ◽

pp. 201-201

Author(s):

P.-H. Tseng

Keyword(s):

Fractured Rock ◽

Flow And Transport

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The Modelling of Multiphase Flow and Transport Processes in Porous Media

Soil & Environment - Contaminated Soil ’95 ◽

10.1007/978-94-011-0415-9_46 ◽

1995 ◽

pp. 221-222

Author(s):

Vincent Lagendijk ◽

Axel Braxein ◽

Christian Forkel ◽

Gerhard Rouvé

Keyword(s):

Porous Media ◽

Multiphase Flow ◽

Transport Processes ◽

Flow And Transport

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Vadose Zone, Part I : Characterization and Flow Processes

Applied Stochastic Hydrogeology ◽

10.1093/oso/9780195138047.003.0016 ◽

2003 ◽

Author(s):

Yoram Rubin

Keyword(s):

Porous Media ◽

Water Flow ◽

Governing Equation ◽

Vadose Zone ◽

Stochastic Analysis ◽

Transport Processes ◽

Richards Equation ◽

Saturated Porous Media ◽

Flow And Transport ◽

Flow Processes

Many of the principles guiding stochastic analysis of flow and transport processes in the vadose zone are those which we also employ in the saturated zone, and which we have explored in earlier chapters. However, there are important considerations and simplifications to be made, given the nature of the flow and of the governing equations, which we explore here and in chapter 12. The governing equation for water flow in variably saturated porous media at the smallest scale where Darcy’s law is applicable (i.e., no need for upscaling of parameters) is Richards’ equation (cf. Yeh, 1998)

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Modeling of Flow and Transport Processes in the Subsurface

Groundwater Updates ◽

10.1007/978-4-431-68442-8_90 ◽

2000 ◽

pp. 477-480

Author(s):

R. Helmig ◽

R. E. Ewing ◽

S. Finsterle ◽

R. Hinkelmann

Keyword(s):

Transport Processes ◽

Flow And Transport

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