Keynote speakers listed in alphabetical order:

Marc Bierkens

Recent advances and outstanding challenges in large-scale hydrological modelling

Marc Bierkens (1965) holds the chair in Earth Surface Hydrology at the Department of Physical Geography at Utrecht University and was acting chairman of the department between 2009 and 2015. Since June 2021 he serves as Vice-Dean of Research for the faculty of Geosciences. He is also partly employed by Deltares. He received his MSc in Hydrology from Wageningen University (1990), a PhD in Physical Geography from Utrecht University (1994) and became professor of Hydrology at Utrecht University in 2002. Between 1994 and 2002 he worked as a senior scientist and team leader at Alterra Research Institute in Wageningen. Marc Bierkens’ fields of expertise are groundwater hydrology, ecohydrology, stochastic hydrology, hydrological regionalisation, congregationalist theory and geostatistics and global hydrology. His current research focuses on global scale hydrological modelling in relation to climate change and water availability. Marc Bierkens is fellow of the American Geophysical Union. He is also a member of the European Geosciences Union and the International Association of Hydrological Sciences and is editor of Water Resources Research. He was chairman of the Boussinesq Center, the network of university hydrology groups in the Netherlands (2007-2011) and of the Netherlands Hydrology Society (2011-2017), which represents over 600 Dutch hydrology professionals. He co-organised the IAHS ModelCARE conference in 2005 in The Netherlands. He was supervisor on 28 completed PhD theses and has been a committee member on 90. Marc Bierkens (co-) authored about 230 publications, 190 of which appeared in international peer-reviewed journals. He is principal author of the book “Upscaling and Downscaling Methods for Environmental Research” (2002), co-author of the book “Sampling for Natural Resource Monitoring” (2006) and editor of the book “Climate and the Hydrological Cycle” (2008).

Rainer Helmig

Coupled free and porous-medium flow processes – models, concepts and analysis

Rainer Helmig is head of the Department of Hydromechanics and Modelling of Hydrosystems in the Faculty of Civil and Environmental Engineering at the University of Stuttgart, Germany His research covers groundwater hydrology, multi-phase flow in porous media, numerical modeling, and the analysis of coupled processes between the unsaturated zone and the atmosphere. Special focus is on coupling hydrosystem compartments and complex flow and transport processes, as well as integrating data and models. Emphasis in on fundamental questions about physical and mathematical modeling of multi-phase processes, developing algorithms accounting for fluid phase changes and structural media heterogeneities, thereby forming a basis for various model concepts (e.g. pre-dimensioning decontamination strategies and analyses of energy storage (gas, heat), including their effects on groundwater). Recent research focuses on understanding and modeling mass- and heat-flux processes across the land/atmosphere interface as controlled by dynamic interactions between the atmospheric boundary layer and the land surface. Contributes to developing new model concepts to enhance understanding of land-atmosphere interactions, evaporation and evapotranspiration processes, climate modelling, and salt precipitation.

Keynote abstract

Coupled systems of free flow adjacent to a porous medium appear ubiquitously in nature and in technical applications. Examples for interface-driven transport and exchange processes include soil evaporation, fuel cell water management or food drying. One of the key challenges for coupled free flow and porous-medium flow arises from the fact that the overall effective behaviour depends strongly on interface processes that occur on small spatial scales (pore scale), although the overall system of interest is often too large to resolve these processes explicitly in detail. REV-scale models are usually not able to capture all the relevant physical processes for such coupled systems. In addition, pore-scale interface roughness, macro-scale surface topologies, and boundary layers strongly influence the flow behaviour inside the porous medium and the free-flow region near the common interface. Pore-scale models are in turn not suitable for large-scale problems because of the high computational costs involved, rendering them applicable only to model domains in the range of micrometres to centimetres. For the accurate description of interface phenomena, it is therefore necessary to develop model concepts that combine information gained through pore-scale and REV-scale models.

In this lecture, we will:

  • explain the relevant processes of mass, momentum and energy transfer at the interface between a free-flow and a porous-media system;
  • present a conceptual model for coupled single-phase free flow and two-phase porous-medium flow with a detailed description of the models in the free flow and in the porous medium;
  • provide a new coupling concept for modelling coupled porous-medium and free flow with application to evaporation and salt-precipitation processes. A comparison study will show the advantages and disadvantages in comparison with classical approaches;
  • present various numerical examples that will illustrate the influence of soil-moisture processes in the subsurface on the groundwater budget and quality.

The results will be compared and discussed with experimental measurements on different scales.

Jan Nordbotten

Numerical methods for coupled hydromechanical problems in fractured rocks

Jan Martin Nordbotten is a professor of mathematics at the University of Bergen, working on problems inspired from geosciences, biology, and biomedicine. He completed his PhD in Bergen in 2004 at the age of 22 as the youngest ever in Norway, and became a full professor when he was 28. He has received national and international recognition for his research, including the inaugural SIAM Geosciences Junior Scientist award in 2009. Nordbotten has published more than 120 papers in collaborations with over 100 researchers, and co-authored together with Michael A. Celia the first text-book on modelling and simulation of subsurface CO2 storage.

Keynote abstract

Fractured rocks are ubiquitous in the subsurface, be it of natural or anthropogenic origin. Consequently, many subsurface resources demand an understanding of flow in fractured rocks to properly be modeled and simulated. An important observation in this respect is that flow through fractured rocks is often driven by pressure gradients that leads to subsurface deformation that is sufficient to significantly impact the stability of fractures. As a consequence, coupled hydro-mechanical analysis is particularly important in this setting.
As a matter of modeling choice, we will in this talk exclusively consider the case where fractures are well represented as lower-dimensional manifolds, which leads to mixed-dimensional equations. In this talk, we will therefore discuss numerical methods for studying this coupled problem of flow and deformation on geometries with embedded lower-dimensional fracture representations. Our emphasis will be on ensuring robust and stable discretizations, applicable to the challenging geometries that can arise from three-dimensional fracture networks.

Adriana Paluszny

Numerical modelling of the poroelastic deformation of geomechanically grown three-dimensional curving fracture patterns and their equivalent permeability

Dr Adriana Paluszny is a Senior Lecturer in the Department of Earth Science & Engineering, Imperial College London. She has a PhD in Computational Geomechanics from Imperial College London and has served as a Post-Doctoral Research Associate in the Rio Tinto Centre for Advanced Mineral Recovery at ICL, as a Research Fellow funded by the UK’s Engineering and Physical Sciences Research Council and the UK’s Natural Environment Research Council. She currently holds a Royal Society University Research Fellowship that allows her to conduct research in the area of fracture mechanics and coupled deformation. Adriana is the recipient of the “Chin-Fu Tsang Coupled Processes Award 2019”, and a member of the “Commission on Coupled Thermal-Hydro-Mechanical-Chemical Processes in Fractured Rock” of the International Society for Rock Mechanics and Rock Engineering. Her research is primarily focused on the robust numerical modelling of multiple fracture growth in three dimensions, with applications to geomechanical modelling of fluid injection, hydraulic fracturing, rock drilling, effective permeability of fractured rocks, and emerging methods in computational fracture mechanics. She is interested in understanding how growth is affected by heterogeneities at multiple scales and how the interplay between fluid flow and mechanics affects these interactions. Adriana also runs the outreach project “Watson Forum”, micro-interviewing women in computational modelling and other STEM areas (

Keynote abstract

Processes governing the growth of fractures in complex media, and their interaction with smaller- and larger-scale discontinuities and material variations, are often investigated using numerical models. The main drawback of these models is that their performance usually depends on the amount of detail included, such as the geometry of the fractures and the distribution of differently shaped embedded inclusions with varying properties. We present the numerical modelling of the poroelastic deformation of three-dimensional fractured rock masses, with non-planar geomechanically grown fractures at multiple scales, with varying apertures, flow through both matrix and fractures, and a fully coupled solution of finite element-based discretisation of the poroelastic equations. Fracture geometry is represented by NURBS surfaces, which are discretised using quadrilaterals, while the matrix is discretised by isoparametric hexahedra. Friction is resolved using an Augmented Lagrangian approach, using the Uzawa iteration method. Matrix heterogeneities are captured as variations in the material properties within the mesh, and the discretisation of the fracture adapts to growth, interaction and fracture permeability. The permeability of the resulting systems is compared to stochastically generated systems of equivalent average properties in three dimensions.

Dominic Reeve

Modelling wave attenuation by vegetation

Dominic Reeve is Professor of Coastal Engineering in the College of Engineering at Swansea University. He led the Energy and Environment research group in the College from 2011 to 2018 and since 2018 he has been the Head of the Zienkiewicz Centre for Computational Engineering, the most prestigious research centre in the College of Engineering. His research interests are coastal flooding, coastal erosion, stochastic modelling, impacts of climate change on beaches. Author of over 300 peer-reviewed journal and conference papers, and contributing author to ‘Handling Uncertainty in Coastal Modelling’ in Flood Risk Science and Management Handbook’, Wiley-Blackwell (2010), ‘Terrestrial laser scanner techniques for enhancement in understanding of coastal environments’, in Seafloor mapping along continental shelves, Springer, (2015). He is the editing author of Coastal Engineering: Processes, Theory and Design Practice, co-author of Hydraulic Modelling – An Introduction: Principles – Methods – Applications and sole author of Risk and Reliability: Coastal and Hydraulic Engineering, all published by SPON/CRC. He is the recipient of the 1995 International Gustave Willems prize by the Permanent International Association of Navigation Congresses for a paper on beach forecasting and the JAMSTEC Nakanishi Award from the Japan Federation of Ocean Engineering Societies, (2016) for work on sea defence reliability.

Keynote abstract

Traditionally, the protection of shorelines has been approached from an engineering perspective, using rock or concrete structures. However, ‘soft engineering’ alternatives which blend in better with their surroundings are gaining popularity as being more sustainable and less harmful to the environment. One form of ‘soft engineering’ is marine vegetation, such as sea grass, which can act as a natural barrier by dissipating wave energy before it reaches the shore. There is a growing literature on detailed analysis of the flow and movement of seagrass under wave and current action. Here, we discuss three types of modelling of the dissipation of waves by seagrass: physical scale models; analytical; and computational. The focus is on whether the attenuation of wave energy can be emulated sufficiently well by a relatively simple description of wave propagation. Specifically, whether the attenuation of waves can be mimicked through the introduction of a linear drag or diffusion term in the momentum equation of the shallow water equations. The equations are solved computationally using a free-damping-error method. Analytical solutions are derived for idealised cases to allow testing of the computational results. In addition, physical modelling of wave attenuation using artificial seagrass are used to provide additional testing of the computational model and the robustness of the analytical solutions. Extremely good agreement was found between analytical and computational results. The physical model results showed best agreement with the computational results when attenuation was mimicked by diffusion for long waves and by linear drag for short waves. 

Monica Riva

Coping with diverse degrees of knowledge in complex subsurface systems

Monica Riva is Professor at the Politecnico di Milano, PoliMI (Italy), Department of Civil and Environmental Engineering. She is also Adjunct Professor at the Department of Hydrology and Water Resources of the University of Arizona (USA). Monica received her Ph.D. in Environmental and Infrastructure Engineering from the PoliMI in 2000. She has been visiting Professor in several Universities and Research Centers, including the University of Arizona, the University of Strasbourg and the CNRS (France). Her research activity has been focused mainly on subsurface flow and transport dynamics, stochastic groundwater hydrology, probabilistic well protection zones, scaling in hydrology and model parameter estimation, uncertainty quantification, multiphase flows and groundwater management. One of her main contributions is the development of exact and approximated formalisms for the characterization of key processes governing spreading of conservative and reactive solutes in hydro-geo-chemically heterogeneous geomaterials by means of a rigorous probabilistic framework. She developed and applied innovative stochastic and upscaling techniques to study flow features of immiscible and miscible fluids. She has developed a theory (based on the concept sub-Gaussian mixtures) able to capture the (typically non-Gaussian) scaling behavior exhibited by many hydrological-hydrogeological-environmental variables. She has introduced novel metrics to perform global sensitivity analysis and ensuing uncertainty quantification across multiple interpretive models with uncertain parameters.
Monica serves as Elected Member of the Council of InterPore (International Society for Porous Media), Deputy Coordinator of the Doctoral Program in Environmental and Infrastructure Engineering at PoliMI and Rector Delegate for International Networks at PoliMI. She has recently coordinated the European Water JPI project “WatEr NEEDs, Availability, Quality and Sustainability”.

Keynote abstract

Modern models of environmental and industrial systems have reached a high level of complexity, with the aim of capturing the nature of target phenomena and applications. With reference to subsurface systems, these include, e.g., multiphase flow and reactive transport in heterogenous aquifers, riverbank filtration systems efficiency, hydrocarbon production allocation for reservoirs and sustainable use of underground resources. The level of complexity of these models could hamper an unambiguous understanding of their functioning, i.e., the way they drive relationships and dependencies among inputs and outputs of interest. Global Sensitivity Analysis (GSA) tools can be employed to examine this issue. In this broad context, emphasis is here devoted to the important aspects related to the way the definition and use of a sensitivity metric is linked to the nature of the question(s) the GSA is meant to address. These aspects are also linked to the use of GSA in designing experimental activities and/or assisting model (stochastic) model calibration.

Jirka Šimůnek

Recent developments and applications of the HYDRUS computer software packages

Jirka Šimůnek is a Professor of Hydrology at the University of California Riverside in the Department of Environmental Sciences. Jirka received an M.Sc. in Civil Engineering from the Czech Technical University and a Ph.D. in Water Management from the Czech Academy of Sciences. His expertise is in numerical modeling of subsurface water flow and solute transport processes, equilibrium and nonequilibrium chemical transport, multicomponent major ion chemistry, field-scale spatial variability, and inverse procedures for estimating the hydraulic properties of unsaturated porous media. He has co-authored over 400 peer-reviewed journal publications and has (according to Google Scholar) an h-factor of 96. His HYDRUS numeric models are used by virtually all scientists, students, and practitioners modeling water flow, chemical movement, and heat transport through variably saturated soils. Dr. Simunek is a Fellow of American Geophysical Union (AGU), American Society of Agronomy (ASA), American Association for Advancement of Sciences (AAAS), and Soil Science Society of America (SSSA). He is a recipient of the Soil Science Research Award (awarded by SSSA in 2019) and the Hydrological Sciences Award (awarded by AGU in 2021). He is currently an Editor-in-Chief of Journal of Hydrology.

Keynote abstract

In this presentation, we will describe new features, new modules, and new developments in the HYDRUS software package. The latest version of HYDRUS-1D has been fully merged with the HYDRUS (2D/3D) software package, dramatically improving its graphical capabilities and extending its compatibility to new Windows-based operating systems. The new modules and capabilities include: a) the Particle Tracking module (to calculate soil water’s transit times and age), b) the Cosmic module (to calculate cosmic-ray neutron fluxes and to use them to estimate large-scale soil hydraulic properties inversely), c) the Dynamic Plant Uptake (DPU) module (to calculate the translocation and transformation of chemicals in the soil-plant continuum), d) the PFAS module (to consider sorption on the air-water interface and the effects of solute concentrations on viscosity and surface tension, and corresponding conductivities and pressure heads), e) the Isotope module (to consider the fate and transport of soil water isotopes with evaporation fractionation), f) the C-Ride module (to consider colloid and colloid-facilitated solute transport), d) new optimization schemes (to dramatically improve the efficiency of the inverse module), and many other new options and graphical capabilities. We will not only describe these new modules and modeling capabilities but also discuss their verification and validation applications.

Dorthe Wildenschild

Characterizing biofilm growth and colloidal deposition and the resulting fluid network alteration in porous media

Dorthe received her Ph.D. and M.S. in Civil and Environmental Engineering from the Danish Technical University. She is a professor of environmental engineering at Oregon State University, conducting research focused on flow and transport in porous media, and addressing research questions concerning subsurface water pollution and energy-related storage. Recent work includes the optimization of geologic storage of anthropogenic CO2 in subsurface reservoirs; exploration of colloid-facilitated transport of contaminants in groundwater; biofilm imaging studies; microbial enhanced oil recovery; and investigations in support of more effective groundwater remediation techniques, including the effects of dynamic flow and wettability changes. She is currently the PI for an NSF-funded instrument development that has brought a state-of-the-art 3D imaging user facility to the Pacific Northwest, USA. In 2014, she was named the annual Darcy Lecturer by the U.S. National Groundwater Association.

Keynote abstract

The increased interest in (and availability of) pore-scale simulations and experimental data for flow and transport in porous systems is facilitating new cross-fertilization among experimentalists and numerical modelers. In the areas of colloid transport and biofilm behavior, there are opportunities for highly detailed experimental characterization that can serve as a seed for new deep learning and machine learning approaches, and to further develop existing pore-scale numerical modeling approaches and theoretical concepts.

This presentation will introduce experimental data on biofilm growth architecture as well as colloid deposition/mobilization in porous media. Both phenomena contribute to alteration/clogging of flow paths, which results in flowlines and nutrient pathways being impeded and/or rerouted. As a result, colloidal transport and biofilm growth architecture is continuously being altered. What has been largely lacking are methods to accurately characterize these evolving networks experimentally. We use x-ray microtomograhy to produce detailed characterization of the porous systems and the processes affecting flow and transport, including measurements not attainable with other types of experimentation.

Both phenomena have great societal impact: Colloid transport affects a variety of environmental and health related fields due to facilitated transport of pathogens, and organic and inorganic contaminants, resulting in clogging of filtration systems, and affecting targeted human drug delivery. Similar areas of relevance apply to biofilm-induced clogging as well. Biofilms are aggregates of microorganisms accumulated at interfaces and the growth of biofilms in media with tortuous geometries (e.g. porous media) is of great scientific interest for of both natural and engineered systems. Examples include: biofouling of mechanical systems; clogging affecting general porous media hydrodynamics, and aiding more traditional remediation efforts; pathogen transmission; and fouling of medical systems and implants.