Groundwater resources represent Germany's most important source of freshwater but they are increasingly under pressure. Climate change, societal developments, and rising abstraction rates are impacting subsurface storage in ways that are currently difficult to predict, affecting both the quantity and quality of groundwater. To ensure sustainable groundwater management, it is crucial to evaluate the intrinsic and spatially variable vulnerability of groundwater systems, especially to prepare for the effects of hydrological extremes. In this context, the groundwater response time, generally defined as the timescale over which a groundwater system responds or adjusts to changes in external or internal conditions and derived here as the characteristic timescale of the aquifer's low-pass filtering behavior, serves as a valuable indicator for vulnerability assessments. Unlike traditional methods, we propose estimating response times through spectral analysis of groundwater level data. Time series from around 200 selected observation wells across Bavaria in Southern Germany were processed and transformed into the spectral domain. Corresponding recharge time series were extracted from high-resolution hydrological model outputs. By integrating these data with hydrogeomorphic information, we fitted a semi-analytical model to the groundwater level spectra to obtain aquifer response times. The semi-analytical solution for the spectral domain accurately reproduced the majority of observed groundwater level spectra. Half of the estimated response times fall between 30 and 100 d. Significant correlation were found between the response time and the depth of the groundwater table. Groundwater systems exhibiting longer response times are interpreted as more resilient to drought conditions and therefore potentially better suited for groundwater abstraction than aquifers with shorter response times.

Reproducibility across diverse high-performance computing (HPC) environments remains a major challenge in computational science, particularly for complex, multi-physics simulation workflows. This study presents a comprehensive approach to achieving bit-for-bit result reproducibility in the context of the OpenGeoSys (OGS) simulation suite. Given the widespread use of OGS in environmental science applications such as safety assessments for radioactive waste disposal and the optimisation of geothermal energy systems our approach enhances the reliability, transparency, and acceptance of simulation results in these safety-critical domains, shown in a case study for far-field deep geological repository assessment. We use GNU Guix to define fully declarative, verifiable software environments and deploy them as portable Apptainer containers, enabling consistent execution across multiple HPC systems. Leveraging AiiDA for workflow automation and provenance tracking, we conduct simulations and complex simulation workflows on three heterogeneous clusters, confirming identical binary-level outputs. The results demonstrate that reproducible and portable software environments can offer a pathway toward long-term verifiability in scientific high-performance computing. We also show how full data provenance originating from software source code and model input data resulting in full simulation workflow result data can be achieved.

In this study, we present a new coupling framework named FINAM (short for “FINAM is not a model”). FINAM is designed to facilitate the coupling of models that were developed as standalone tools in the first place and to enable seamless model extensions by wrapping existing models into components with well-specified interfaces. Although established coupling solutions such as Earth System Modeling Framework (ESMF), Ocean Atmosphere Sea Ice Soil (OASIS), or Yet Another Coupler (YAC) focus on highly parallel workflows, complex data processing, and regridding, FINAM prioritizes usability and flexibility, allowing users to focus on scientific exploration of coupling scenarios rather than technical complexities. FINAM emphasizes ease of use for end users to create, run, and modify model couplings, as well as for model developers to create and maintain components for their models. The framework is particularly suited for applications where rapid prototyping and flexible model extensions are desired. It is primarily targeting environmental models, including ecological models for animal populations, individual-based forest models, field-scale crop models, economical models, and hydrological models. Python's robust interoperability features further enhance FINAM's capabilities, allowing us to wrap and use models written in various programming languages like Fortran, C, C++, Rust, and others. This paper describes the main principles and modules of FINAM and presents example workflows to demonstrate its features. These examples range from simple toy models to well-established models like OpenGeoSys and Bodium covering features like bidirectional dependencies, complex model coupling, and spatiotemporal regridding.

Regional groundwater modelling can provide decision-makers and scientists with valuable information required for the sustainable use and protection of groundwater resources in the future. In order to assess and manage the impact of climate change on regional aquifer systems, numerical groundwater models are required which represent the subsurface structures of aquifers and aquitards in 3D at the regional scale and beyond in the most efficient way. A workflow to clearly generate these structural subsurface representations from a variety of data sources is introduced, applying open-source Geographical Information Systems. The resulting structural models can be used with finite element method-based simulation tools, such as the open-source environment OpenGeoSys. The preparation workflow of the structure model is presented for a large river basin in Germany, indicating the applicability of the method even in a challenging hydrogeological region with several stockworks of dipped and fractured sedimentary aquifers, partially showing significantly changing hydraulic conditions due to natural lateral facies changes.

<p>Groundwater resources are heavily exploited to supply domestic, industrial and agricultural water consumption. Climate and societal changes and associated higher abstraction will alter the subsurface storage in terms of quantity and quality in currently unpredictable ways. In order to ensure sustainable groundwater management, we must evaluate the intrinsic and spatially variable vulnerability of aquifers in terms of water quality issues and the resilience of groundwater volumes to external perturbations such as severe droughts in connection with intensive irrigation. For this purpose, physically based numerical groundwater models are of great importance, especially on the regional scale. The equations applied in these models must be fed with the hydrogeological parameters: The <strong>transmissivity <em>T</em></strong> and the <strong>storativity <em>S</em>.</strong></p> <p>Both parameters are typically obtained through time consuming and cost intensive hydrogeological in-situ tests or by laboratory analysis of core samples from point information (drillings and wells), resulting in parameters with limited transferability to regional settings. Instead, we propose to determine the parameters by spectral analysis of groundwater level fluctuations using (semi-)analytical solutions for the frequency domain. We developed a fully automatized workflow, taking groundwater level and recharge time series together with little information about the geometry of the aquifer to derive <strong><em>T</em></strong> and <strong><em>S</em></strong><em> </em>as well as<strong><em> t<sub>c</sub></em></strong> (<strong>the characteristic response time</strong>). While the first two will be used for hydrogeological modelling, the latter can serve as an indication to assess the resilience of the groundwater system directly without additional modelling attempts. The methodology was tested with great success in simplified numerical environments and was applied to real groundwater time series in southern Germany. The response times and the storativities could be robustly estimated while the transmissivities inherit quantifiable uncertainties. Depending on the hydrogeological regime, the parameters represented effective and regional estimates.</p>

AbstractIn this chapter we briefly describe information methods and technologies supporting geotechnical systems analyses of to large extend, i.e. using virtual reality methods for data and model integration (Sect. 5.1) and improving computational efficiency by using high-performance-computing techniques (Sect. 5.2).

Success of our ongoing energy transition largely depends on subsurface exploitation. The subsurface can act as a “battery” to store energy dense fluids such as hydrogen, or a “host” to sequester unwanted substances such as carbon dioxide or radioactive waste. On the other hand, these operations cause the subsurface pressure and/or temperature to change and induce various (or cyclical) loadings to the surrounding formations. Their operational safety crucially hinges upon the subsurface integrity. The most imminent risk is nucleation of cracks that can lead to loss of mechanical integrity. Unlike hydraulic fracturing in geoenergy applications where one deliberately initiates cracks at certain targets, we normally design a system to avoid fracturing. At the designing stage, we thus have no prior knowledge of crack initiation locations or propagation paths. And, the computational designing tools should be able to assess the fracturing risk without such prior knowledge. In this study, we compared three computational approaches that do not require prescribed crack geometries—the discrete element method, the lattice element method, and the variational phase-field approach—against percolation experiments on rock salt. The experimental results show different fracture propagation paths depending on the boundary loads. The fracture geometries were reasonably matched by all approaches despite some differences in path irregularities. While the variational phase-field approach predicts relatively regular fracture paths, the paths predicted by the discrete and the lattice element methods are more irregular. These irregularities may seem more comparable to intergrain failure in real rocks, but they are also necessary triggers for fracture initiation in the discrete and the lattice element methods. In contrast, the fracture initiation in the variational phase-field approach is a realization of the energy minimization in the system, and the grain level descriptions are absent in the current formulation. These findings highlight their predictive capabilities and gaps to be bridged between the grain and continuum scales for field-scale applications.

Horizontal cavern structures are discussed as a means to constructing energy storage facilities in bedded salt formations. During their design, the spacing of injection and discharge boreholes for solution mining is an important variable determining cavern length, shape and construction cost, but also influencing the long-term mechanical behavior during the storage of oil or gas. Increasing the borehole spacing has been suggested in order to increase cavern capacity and construction rate while decreasing construction cost but its mechanical consequences have yet to be explored. In this paper, cavern geometries constructed with different borehole spacings are obtained using a solution mining simulation model. Static creep analyses have been conducted based on these geometrical models to discuss the impact of the maximum cavern length on the mechanical behavior of the caverns. The results show that the creep deformation of the horizontal cavern induces limited volume change depending on operating pressures. Increasing the length of the cavern initially increases cavern roof displacement and volumetric convergence, but plateaus after a length 600 m, i.e. 5 to 6 times the cross-sectional diameter. A similar behavior is observed in terms of selected integrity criteria. The results indicate the principal possibility to access larger storage volumes and higher construction speed by increasing the borehole spacing to longer than 5 to 6 times the designed cross-sectional diameter. (c) 2022 Elsevier Ltd. All rights reserved.

The operator splitting approach has been widely accepted since it was introduced as a means to solve reactive transport problems. The conventional operator-splitting finite element scheme (Nodal-OS) handles speciation calculations on nodes, resulting in a mixing of heterogeneous reactions on opposing sides in multi-layer systems. Such mixing, however, is not physically accurate. In this context, we propose a new operator-splitting finite element scheme (IP-OS) for reactive transport modeling in saturated porous media. In contrast to the conventional scheme, speciation calculations are performed on integration points rather than on nodes in the new scheme. The implementation of the IP-OS scheme is verified through comparison with an analytical solution of a coupled diffusion–dissolution problem. On this basis, two representative benchmarks are used to examine the advantages and disadvantages of IP-OS. IP-OS is found to have the following advantages and disadvantages compared to Nodal-OS: (1) IP-OS is more accurate; (2) IP-OS is more straightforward to implement; (3) IP-OS is less sensitive to grid resolution and is numerically more stable with coarser grid spacing; and (4) IP-OS is computationally more expensive. In light of the above pros and cons, we recommend using Nodal-OS in cases where chemical reactions do not affect transport properties, and IP-OS in multi-layer heterogeneous cases where chemical reactions alter transport properties of porous media. • A new operator-splitting finite-element scheme is developed for reactive transport modeling in saturated porous media. • Compared to the widely used scheme, the new scheme is less sensitive to grid resolution and numerically more stable. • The new scheme is favored for multi-layer heterogeneous cases where chemical reactions alter transport properties of porous media.

Management of energy waste such as high-level waste (HLW) disposal in deep geological repositories is one of most pressing challenges in the context of nuclear energy. The general research question addressed in the present work is how to represent coupled physical processes after the emplacement of heat-emitting waste in such a repository in claystone at multiple scales by numerical models and how can they validated by experimental results in underground research laboratories. Numerical modelling of the coupled thermal hydraulic mechanical (THM) processes to assess the long-term safety of deep geological repositories rests on adequate constitutive laws and quantification of in-situ host rock material properties during long-term heating as well as a reliable numerical approach for solving the underlying governing equations. For this purpose, various in-situ experiments have been conducted in the Callovo-Oxfordian claystone (COx) at the Meuse/Haute-Marne (M/HM) Underground Research Laboratory (URL) by the French National Radioactive Waste Management Agency (ANDRA) since 2003. A subset of these is investigated here using a numerical THM model employed at different spatial scales. Two main results were achieved. First, the previously developed numerical THM model (Wang et al., 2021) has been compared agains in-situ experimental data from the full-scale heating (ALC) experiment at the M/HM URL in an attempt to validate the model. The numerically simulated temperature and pore pressure data of the ALC experiment are in good agreement with in-situ measured data. This model was then employed to simulate fully coupled THM processes of an entire repository section for High-Level Waste (HLW) in a COx clay formation according to the Cigeo project by ANDRA. This upscaling was enabled by running the numerical code on high-performance-computing platforms. Three-dimensional, fully coupled and efficient THM models for the numerical simulation of deep geological repositories such as the one presented in this study will help in the design of nuclear waste repositories under realistic geological conditions. Moreover, the present work is a contribution to Task E of the DECOVALEX-2019 project for model validation and comparison against experimental results (Plúa et al., 2021; Seyedi et al., 2020).

Earth System Models (ESM) got much more demanding over the last years. Modelled processes got more complex and more and more processes are considered in models. In addition resolutions of the models got higher to improve accuracy of predictions. This requires faster high performance computers (HPC) and better I/O performance. One way to improve I/O performance is to use faster file systems. Last year we showed the impact of the ad-hoc file system on the performance of the ESM EMAC. An ad-hoc file system is a private parallel file system which is created on-demand for an HPC job using the node-local storage devices, in our case solid-state-disks (SSD). It only exists during the runtime of the job. Therefore output data have to be moved to a permanent file system before the job has finished. Performance improvements are due to the use of SSDs in case of small chunks of I/O or a high amount of I/O operations per second. Another reason for a performace boost is because the running job can exclusively access the file system. To get a better overview in which cases ESMs benefit from using ad-hoc file systems we repeated our performance tests with further ESMs with different I/O strategies. In total we now analyzed EMAC (parallel netcdf), ICON2.5 (netcdf with asynchronous I/O), ICON2.6 (netcdf with Climate Data Interface (CDI) library) and OpenGeoSys (parallel VTU).

The present paper gives an overview of the GeomInt project “Geomechanical integrity of host and barrier rocks—experiment, modelling and analysis of discontinuities” which has been conducted from 2017–2020 within the framework of the “Geo:N Geosciences for Sustainability” program. The research concept of the collaborative project is briefly introduced followed by a summary of the most important outcomes. The research concept puts geological discontinuities into the centre of investigations—as these belong to the most interesting and critical elements for any subsurface utilisation. Thus, while research questions are specific, they bear relevance to a wide range of applications. The specific research is thus integrated into a generic concept in order to make the results more generally applicable and transferable. The generic part includes a variety of conceptual approaches and their numerical realisations for describing the evolution of discontinuities in the most important types of barrier rocks. An explicit validation concept for the generic framework was developed and realised by specific “model-experiment-exercises” (MEX) which combined experiments and models in a systematic way from the very beginning. 16 MEX have been developed which cover a wide range of fundamental fracturing mechanisms, i.e. swelling/shrinkage, fluid percolation, and stress redistribution processes. The progress in model development is also demonstrated by field-scale applications, e.g. in the analysis and design of experiments in underground research laboratories in Opalinus Clay (URL Mont Terri, Switzerland) and salt rock (research mine Springen, Germany).

AbstractThe FFS method (see Sect. 10.1007/978-3-030-61909-1_3) was developed to simulate direct shear tests. To provide a tool for the project work and get things easier done a graphical user interface (GUI) was also created. The GUI simply calls all necessary functions by letting the user either fill form fields or choose input files from the working folder. The rock parameters and the conditions of the direct shear test with the normal stress levels and shear displacements have to be selected. If an experiment is simulated the lab results can be selected as a text file so a visual comparison is possible. The geometry has to be loaded as a point cloud or an artificial surface can be generated. With small modifications the code can do multiple executions using artificial surfaces.

It is commonly accepted that the processes determining how plant-groundwater interactions influence vegetation patterns depend on subsurface properties, including groundwater availability, but not much is known about the underlying processes. We present a hybrid process-based simulation system to study the feedback between vegetation and subsurface hydrodynamics using mangroves as an example. Our approach relies on first principles rather than on empirical competition concepts. We develop a modular tool which dynamically couples an agent-based vegetation model to a continuum groundwater model. The vegetation model describes individual trees and their interactions within their environment and communities. We show the dependence of the salinity distribution on aquifer properties within stylized case studies. Moreover, the model predicts varying tree allomanes depending on variations of subsurface properties. Finally, we analyze the nature of belowground competition for fresh water as a direct consequence of the plant-soil feedback that is inherent to the modelling approach. The results show that the interaction of vegetation and subsurface hydrodynamics is crucial for vegetation zonation patterning in form of a pronounced distribution of tree allometry. We also discuss the benefits and disadvantages of our presented plant-soil feedback modelling approach, as well as its implications for future research.

1. Introduction The availability of reliable information describing our natural and anthropogenic environment—and its changes in particular—is crucial for understanding the complexity of structures and pro-cesses within environmental systems. Modern remote sensing and monitoring methods provide an increasing amount of environ-mental data that can be used for a variety of management purposes [1,2].

In a geothermal system, unstable fluid density profiles due to temperature variations can trigger the onset and development of free thermal convective processes (J.W. Elder. Transient convection in a porous medium. (Elder in J Fluid Mech 27: 609–623 , 1967, Elder 1967). Early studies on the problem showed that the development of free thermal convection in the Earth’s crust require a relatively high permeability of the porous rocks (Lapwood in Math Proc Camb Philos Soc, 44:508–52, 1948, Lapwood 1948). Since the permeability inside the damaged area of major fault zones can far exceed the permeability of the enclosing rocks (Wallace, Morris in PAGEOPH, 124:107–125, 1986, Wallace and Morris 1986), one can expect the development of free thermal convective instabilities to occur in such tectonically perturbed rocks. The onset of thermal convection of a single-phase fluid in a vertical fault enclosed in impermeable rocks was considered in a full 3D approximation by Wang, Kassoy, Weidman (Int J Heat Mass Trans, 30:1331–1341, 1987, Wang et al. (1987)). A fundamental result of those investigations was that highly permeable faults allow for onset of free thermal convection even under a normal (e.g. 30 $$^{\circ }\mathrm{C}\cdot \mathrm{km}^{-1}$$ ) geothermal gradient. In contrast to simple homogenous 1D and 2D systems, no appropriate analytical solutions can be derived to test numerical models for more complex 3D systems that account for variable fluid density and viscosity as well as permeability heterogeneity (e.g. presence of faults). Owing to the efficacy of thermal convection for the transport of thermal energy and dissolved minerals in the moving fluid, a benchmark case study for density/viscosity driven flow is crucial to ensure that the applied numerical model accurately simulates the physical processes.

Abstract. Most large-scale hydrologic models fall short in reproducing groundwater head dynamics and simulating transport process due to their oversimplified representation of groundwater flow. In this study, we aim to extend the applicability of the mesoscale Hydrologic Model (mHM v5.7) to subsurface hydrology by coupling it with the porous media simulator OpenGeoSys (OGS). The two models are one-way coupled through model interfaces GIS2FEM and RIV2FEM, by which the grid-based fluxes of groundwater recharge and the river–groundwater exchange generated by mHM are converted to fixed-flux boundary conditions of the groundwater model OGS. Specifically, the grid-based vertical reservoirs in mHM are completely preserved for the estimation of land-surface fluxes, while OGS acts as a plug-in to the original mHM modeling framework for groundwater flow and transport modeling. The applicability of the coupled model (mHM–OGS v1.0) is evaluated by a case study in the central European mesoscale river basin – Nägelstedt. Different time steps, i.e., daily in mHM and monthly in OGS, are used to account for fast surface flow and slow groundwater flow. Model calibration is conducted following a two-step procedure using discharge for mHM and long-term mean of groundwater head measurements for OGS. Based on the model summary statistics, namely the Nash–Sutcliffe model efficiency (NSE), the mean absolute error (MAE), and the interquartile range error (QRE), the coupled model is able to satisfactorily represent the dynamics of discharge and groundwater heads at several locations across the study basin. Our exemplary calculations show that the one-way coupled model can take advantage of the spatially explicit modeling capabilities of surface and groundwater hydrologic models and provide an adequate representation of the spatiotemporal behaviors of groundwater storage and heads, thus making it a valuable tool for addressing water resources and management problems.