This session aims at stimulating an interdisciplinary discussion about the state of the art and recent advances about soil—water constitutive laws and soil physical and hydrological properties, in the framework of a continuum approach and contributing to define its limits.
Experimental, theoretical and numerical contributions are encouraged about, but not limited to, (1) scaling of soil—water constitutive laws and their changes in time and space as a consequence of seasonality, climatic changes, anthropogenic changes and pedogenesis; (2) physics of water—repellent soils, and of swelling, dispersive and collapsible soils; (3) constitutive laws for extremely dry conditions and for nearly saturated soils; (4) nonequilibrium and hysteretic behaviours; (5) limits of the Darcian approach in the presence of macroporosity; (6) heat transfer and dispersion; (7) freezing and thawing processes in permafrost; (8) mechanisms of incipient erosion; (9) mathematical functions of constitutive laws and their physical implications; (10) pedotransfer functions and database analysis.
Advancements along those lines will have major implications in many fields, ranging from hydrology, to soil science and soil physics, agriculture and geotechnics.
Interflow in seasonally frozen soils plays a key role in winter runoff generation and groundwater recharge. Uncertainty in the physical processes governing soil freezing has resulted in a wide range of parameterisations to capture ice-induced changes in pore-space connectivity. Although several numerical models for partially frozen soils have implemented these parameterisations, their impact on interflow development has not been systematically assessed.
In this work, we investigate how different hydraulic parameterisations of frozen soils influence interflow dynamics in sloping terrain. We compare three published parameterisations: (i) a capillary-bundle model following Watanabe and Flury (2008), (ii) an impedance-factor-based reduction of hydraulic conductivity, and (iii) a drying assumption in which ice formation reduces liquid water availability. To compare them, we developed a two-dimensional finite volume solver for coupled heat and water transport. This unified framework, implemented in JAX to enable high-performance computing in Python, allows us to isolate parameterisation effects from numerical artefacts. We conduct two-dimensional simulations to analyse the dynamics of interflow during freezing and thawing periods. The results show substantial differences in both the timing and intensity of interflow among the parameterisations.
Our findings demonstrate that the choice of frozen-soil hydraulic parameterisation can strongly affect simulated runoff and infiltration partitioning. These results underscore the importance of parameterisation choice for hydrological modelling in cold regions with increasingly frequent midwinter melt events.
Watanabe K., Flury M. Capillary bundle model of hydraulic conductivity for frozen soil. Water Resour. Res., 44(12), 2008. doi:10.1029/2008WR007012.
How to cite: Hermann, A., Drews, R., and Cirpka, O.: Modelling Interflow in Seasonally Frozen Soils: A Comparison of Hydraulic Parameterisations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13228, https://doi.org/10.5194/egusphere-egu26-13228, 2026.
The van Genuchten-parameterization (vG) of the soil water retention curve (SWRC) has been very popular for over four decades, but it has some physical inconsistencies at the dry and the wet end. The recently introduced Rossi–Ippisch–Adaptation (RIA) of vG resolves these by introducing an air-entry value and eliminating the residual water content. Unlike any other parameterization of the SWRC, RIA can transition smoothly from a sigmoidal vG-type curve to a power-law Brooks-Corey curve. We elucidate how α determines the existence and location of an inflection point, which determines if the resulting curve is sigmoidal or not. We also present a criterion to determine the limit at which the RIA curve converges to the more parsimonious Brooks–Corey power-law form. As a preparation for future work, we explored if a hysteric version of RIA is feasible. Expressions for its main drying and wetting curves are provided, showing that hysteresis in RIA necessarily induces hysteresis in the shape parameters α and n. A practical closed-form relation is proposed to estimate a hysteretic parameter set for the main wetting curve when measurements are only available for the main drying curve.
How to cite: de Rooij, G. H. and Nambiar, A.: A soil water retention curve that can transition between Brooks-Corey and van Genuchten can be made hysteric in principle., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12092, https://doi.org/10.5194/egusphere-egu26-12092, 2026.
The soil-water constitutive relationship was first introduced by Terzaghi for pore fluid pressure driven one-dimensional consolidation [1]. M. A. Biot later established a three-dimensional constitutive relationship for pore-saturated soil system [2]. The interaction between porous media and fluid is a complex coupled phenomenon governed by the intricate relationship between the soil matrix and the pore-occupying fluid. Closed form solutions of this poroelastic model can only be obtained for highly simplified cases. Numerical modelling is widely accepted method for simulating the poromechanical scenarios. An Open-Source based model, satBiotFoam, is developed over the Finite-Volume (FV) based framework of OpenFOAM® for solving coupled poromechanical problems. The proposed model employs an iterative approach based on mathematical operator splitting to eliminate non-physical oscillations. The presented model is capable of accurately capturing coupled interaction validated against widely accepted benchmark solutions. This coupled constitutive relationship is characterized by a non-monotonic pressure variation in deforming porous media or pumped aquifer systems. This phenomenon was first reported from the well fields of Noordbergum village in the Netherlands by Verruijt [3]. Noordbergum and Reverse Noordbergum Effects are such poromechanical phenomena which can be captured using the proposed model. The present works aims to characterize these phenomena under various homogeneous and heterogeneous domains, demonstrating the applicability of the model for poromechanical applications near pumping and recharging wells. A variety of two- and three-dimensional problems are presented related to soil deformation and pumping in aquifer-aquitard systems with physically consistent solutions. Findings of the proposed work aims to understand the critical physical relationship among pore fluid and heterogenous/homogeneous soil systems under aquifer pumping or recharging scenarios.
References:
[1] Terzaghi, C., 1925. Principles of soil mechanics: V-physical differences between sand and clay. Eng. News Rec. 96, 912–915.
[2] Biot, M. A. (1941). General Theory of Three‐Dimensional Consolidation. Journal of applied physics, 12(2), 155-164.
[3] Verruijt, A., 1969. Elastic storage of aquifers. In: Flow Through Porous Media, vol. 1. San Diego, California, pp. 331–376.
How to cite: Srivastava, H. and Dhar, A.: Numerical Modelling of Noordbergum Effect Using Coupled Poromechanics Approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17566, https://doi.org/10.5194/egusphere-egu26-17566, 2026.
Physics-informed neural networks (PINNs) have recently attracted increasing attention as a data-efficient framework for solving partial differential equations governing complex subsurface flow processes. PINNs provide a promising alternative to conventional numerical methods for modeling unsaturated soil water flow, which is typically described by highly nonlinear governing equations. However, when applied to complex infiltration problems, conventional PINNs often suffer from imbalanced loss terms associated with initial conditions, boundary conditions, and governing equation residuals, leading to slow convergence and suboptimal accuracy.
In this study, a Loss-Attention Physics-Informed Neural Network (LAPINN) framework is employed to simulate unsaturated infiltration processes under both steady-state and transient conditions. The employed framework incorporates a loss-attention mechanism that adaptively reweights individual loss components during training, enabling the network to dynamically focus on regions and constraints that are more difficult to satisfy. This adaptive strategy effectively alleviates loss imbalance and enhances training stability without requiring manual tuning of loss weights.
The performance of LAPINN is systematically evaluated using three representative benchmark problems: (1) one-dimensional steady-state unsaturated infiltration, (2) one-dimensional transient unsaturated infiltration, including an inverse problem for hydraulic parameter identification, and (3) two-dimensional transient unsaturated infiltration with a prescribed Dirichlet boundary condition at the soil surface. Both forward and inverse modeling capabilities of the proposed framework are investigated.
The results demonstrate that LAPINN consistently outperforms standard PINNs in terms of prediction accuracy and convergence efficiency across all benchmark cases. In addition, the proposed method enables reliable inversion of hydraulic parameters using limited observational data. These results indicate that LAPINN provides a robust and efficient computational framework for modeling unsaturated soil water flow and offers strong potential for data-scarce hydrological and geotechnical applications.
How to cite: Li, J., Song, Y., Zhou, P., Ren, J., Khan, A., and Chen, X.: Modeling Unsaturated Soil Water Transport Based on Loss-attentional Physics-informed Neural Networks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12089, https://doi.org/10.5194/egusphere-egu26-12089, 2026.
Since the Quaternary Pleistocene, the estuary region of the Yangtze River in China has undergone extensive sedimentation due to the combined effects of tectonic movements, ancient river systems, paleo-marine environments, and other geological factors, resulting in a thick sequence of Quaternary deposits exceeding hundreds of meters in depth. In engineering practice, the complex interaction between groundwater conditions and soil has led to incidents of foundation pit instability. Previous research on ensuring the safety of foundation pit construction under such geotechnical conditions has primarily focused on catastrophic phenomena such as soil piping and boiling; however, these studies often fail to adequately explain certain accidents that occur without evident signs of such failures. This study investigates the micro-scale migration and structural reorganization of soil particles induced by groundwater seepage, using the foundation pit project of Nantong Metro as a case study. A combination of physical model testing and discrete element method (DEM) simulations is employed to analyze the underlying mechanisms. The results indicate that soil settlement resulting from pore water pressure dissipation due to groundwater level fluctuations is significantly smaller than the differential settlement caused by seepage forces. The formation of a "sand-clay" dual structure in the soil is attributed to the combined influence of marine and fluvial sedimentation processes. The loss of clay particles induces compression of the sand skeleton, which constitutes the primary mechanism responsible for macroscopic soil mass settlement. Specifically, localized leakage at weak zones of the waterproof curtain can trigger fine particle loss and progressive weakening of the silt layer structure, leading to uneven settlement, lateral displacement, or even instability of the retaining system—posing significant risks to foundation pit safety.
How to cite: Zou, P. and Deng, Y.: Environmental effects of dewatering procedure when subway's deep excavation in marine continental sedimentary soil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7139, https://doi.org/10.5194/egusphere-egu26-7139, 2026.
Agricultural farmland requires a delicate balance between providing sufficient water to crops and draining away excess moisture. This drainage is normally achieved through digging trenches that run through farming areas, allowing surplus water to flow away as surface runoff, contributing to river networks downstream. This drainage is soil-dependent and mostly uncontrolled, resulting in excessive water losses at critical points throughout the year, especially during dry periods. This water might have contributed to plant growth otherwise.
To address this issue, the Wasserwirtschaftsamt Ansbach is leading a pilot project that aims to retain part of this excess water before it is lost as runoff. By installing overflow weirs along agricultural trenches, water can be temporarily stored and allowed to infiltrate back into the soil when moisture levels are low.
The project “Grüne Gräben” aims to investigate the effects of these weirs on both local and regional scales. Using numerical models, it is possible to quantify how much water is retained and subsequently re-infiltrated into the soil system. To achieve this, the project utilizes HydroGeoSphere (HGS), an integrated, physically based hydrological model that simulates interactions between surface water, unsaturated soil, and groundwater. Unlike simplified conceptual models, HGS numerically solves the Richards equation for variably saturated flow in the porous medium together with the diffusion wave equation for overland flow. This coupling allows for a detailed understanding of the interaction between the stored surface water and resultant infiltration into the unsaturated zone over space and time.
The meteorological, soil moisture, and soil textural data collected from field excursions are used to calibrate and validate the models. Parameters such as hydraulic conductivity, porosity, and soil-water retention characteristics allow for an assessment from a physically based approach. Additionally, vegetation and root growth provide a realistic representation of the evapotranspiration resulting from crop growth and harvesting. This, along with the infiltration resulting from the presence of the weir, helps determine the extent of evapotranspiration enhancement from the newly available soil moisture.
By modelling scenarios with and without overflow weirs, Hydrogeosphere provides data on the net benefit of installing such land management practices. The outcomes of these studies help in gauging whether this practice is worth scaling to other farms around Bavaria with similar soil characteristics.
How to cite: El Hajjar, S., Keßel, N., Broich, K., Disse, M., and Scherer, N. T.: Impact of Overflow Weirs on Unsaturated Soil Water Dynamics in Agricultural Farmland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10807, https://doi.org/10.5194/egusphere-egu26-10807, 2026.
In this memory we report about aims, methods and present findings of the WormEx II experiment. The WormEx II experiment is a 4-years lasting educational experiment and a citizen-based participatory research (CBPR) performed in high-school classes, in view of attracting students’ attention on the hydrological role of healthy soils, through the observation and quantification of earthworm digging activity and of its hydrological role.
The core of the experiment consists in replicating Charles and Horace Darwin’s famous observations on the sinking of stones, published in 1881 and 1901 respectively. We reproduced a couple of wormstones (inspired by that positioned by Horace Darwin at Down House), and we placed them in the garden of the Liceo Copernico high-school in Brescia in March 2022. Since then many sinking measurements and infiltration tests (with different earthworm activity) were performed with the participation of high-school and university students, teachers and faculty staff.
The analysis of the experiment is multi-faceted and deserves intriguing interpretative keys. Firstly students meet Charles and Horace Darwin’s original works on the matter, thus (partially or integrally) reading them, under the guidance of the teachers. They go in depth with the text analysis and through their data, recognizing both Charles’ rigorous epistemological approach based on ample data collection and Horace’s attitude at designing a replicable experiment to obtain controlled and good quality data. This introduces them to the dialectics between data collection and experiment design and replicability, standing at the basis of modern Hydrology and of many natural sciences. Contextually they deal with the scientific relevance of patient practice and long lasting series. According to Charles Darwin’s definition of «minima», students appreciate how meaningful changes in Nature are mostly given by the continue and reiterated superimposition of minimal ones. They observe aspects of earthworm ecology, regarding their digging activity into relationship with the antecedent meteorological conditions and recognize the soil attitute at behaving as a low-pass filter of the meteorological variability.
Finally, by means of managing the datasets of the sinking and of the micrometeorological measures, and interpreting the infiltration tests, they qualitatively and quantitatively compare their findings with ancient ones, and approach the issue of quantitative treatment of data and of scientific reporting, thus attempting to overcome the mainly qualitative approach of most CBPR activities.
How to cite: Barontini, S., Camplani, A., Curti, E., Ferrari, M., Grossi, G., Marra, M., Peli, M., and Vitale, P.: From teaching the hydrological functions of healthy soils to CBPR through a replica of Charles and Horace Darwin’s observations on the action of worms, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20211, https://doi.org/10.5194/egusphere-egu26-20211, 2026.
Farmers face increasingly more uncertainty with regards to crop production of due to a changing climate. Temperature and precipitation patterns change, with prolonged periods of heats and droughts. This affects the crop growth season in terms of overall duration and increases the uncertainty of the crop growth conditions. Especially crop water availability is of importance to generate a good yield. Various management strategies can help to manage the water availability, such as drainage, irrigation infrastructures or a combination of both. Within the EU FARMWISE project, various water management strategies are evaluated that could help farmers mitigate future extreme weather conditions. The goal is to determine how various irrigation strategies perform under future climatic conditions.
The management strategies under investigation are traditional sprinkler irrigation, subirrigation and a combination of controlled subirrigation with tile drainage. Utilising HydroGeoSphere (HGS), a 3D physics-based integrated surface-subsurface model was setup of an experimental field in the Netherlands. At the field site, an irrigation system, comprising of a controlled drainage with subirrigation is being monitored. The HGS model was calibrated using the field data to simulate the natural groundwater fluctuations, as well as the controlled drainage and subirrigation.
To determine the effectiveness of the water management scenarios under various climatic scenarios, the water management scenarios were implemented into the calibrated model. The hydraulic head response and soil moisture content were the parameters of interest. To represent the future climate scenarios, precipitation and evapotranspiration from the SSP1-2.6, SSP2-4.5 and SSP5-8.5 scenarios over three time horizons were used. All model results in terms of hydraulic head and soil moisture response are currently being analysed to determine the effectiveness of the various management strategies under different climates.
How to cite: de Bruin, J., van der Ploeg, M., Rakonjac, N., Bartholomeus, R., de Wit, J., and Mustafa, S.: Simulating agricultural water management strategies using an integrated surface subsurface hydrological model under future climatic extremes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19624, https://doi.org/10.5194/egusphere-egu26-19624, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot A
EGU26-8945 | ECS | Posters virtual | VPS8
Numerical Modelling of Drip Irrigation to Improve Water Use Efficiency in Semi-Arid AgroecosystemsTue, 05 May, 14:33–14:36 (CEST) vPoster spot A
In arid and semi-arid regions, the agriculture thrives on the use of irrigation systems such as drip and sprinkler irrigation which ensures the higher irrigation application efficiencies. However, the planning and design of drip irrigation systems continue to rely on generic understanding and manual hydraulic calculations which often leads to sub-optimal performance. The present study addresses this gap by using a numerical model for analysing the drip irrigation for Okra Cultivation in a semi-arid district of Udaipur, Rajasthan, India. Therefore, the objectives of this study are analysing the hydraulic performance of the given network of drip irrigation using a numerical model and evaluate its adequacy and operational efficiency.
The hydraulic adequacy is determined using EPANET 2.2 modelling tool employing pressure driven demand (PDD) approach. The temporal variability in the behaviour of system was captured by running the extended period simulation model. The model incorporates operational control rules to define the variable demands for the different phases of the growth of the plant and scheduling the pump and valve operations thereby enabling the digital twin of the drip irrigation system. The source of water taken as well is explicitly represented in the model while the filtration unit is represented as a non-return valve with high loss coefficient. In addition to the watering, the fertigation of the crops is also simulated in the model according to the fertigation schedule.
The hydraulic performance of the irrigation system is evaluated using standard performance indicators such as the Coefficient of Uniformity, Coefficient of Variation, and Distribution Uniformity. Furthermore, the reliability of system performance is assessed using network reliability parameter. Thus, the study will assist farmers and stakeholders in achieving optimal operation of drip irrigation systems by addressing and minimizing the multiple technical and operational challenges associated with this irrigation method.
How to cite: Gupta, K.: Numerical Modelling of Drip Irrigation to Improve Water Use Efficiency in Semi-Arid Agroecosystems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8945, https://doi.org/10.5194/egusphere-egu26-8945, 2026.
