HS8.3.2 | Vadose Zone Hydrology: Advances and Future Perspectives in Soil Hydrologic Processes
EDI
Vadose Zone Hydrology: Advances and Future Perspectives in Soil Hydrologic Processes
Co-organized by SSS6, co-sponsored by ISMC
Convener: Roland Baatz | Co-conveners: Thomas Baumgartl, Stefano Ferraris, Teamrat Ghezzehei, Martine van der Ploeg, Harry Vereecken
Orals
| Mon, 15 Apr, 08:30–12:30 (CEST)
 
Room B, Tue, 16 Apr, 08:30–10:15 (CEST)
 
Room B
Posters on site
| Attendance Mon, 15 Apr, 16:15–18:00 (CEST) | Display Mon, 15 Apr, 14:00–18:00
 
Hall A
Posters virtual
| Attendance Mon, 15 Apr, 14:00–15:45 (CEST) | Display Mon, 15 Apr, 08:30–18:00
 
vHall A
Orals |
Mon, 08:30
Mon, 16:15
Mon, 14:00
This session aims to bring together scientists working in the field of vadose zone hydrology across spatial scales ranging from the pore- to the catchment- and continental scale. Recent regional and continental-scale drought events and flood events urge the need for better understanding the role of vadose zone processes in the Earth system. The state of the vadose zone controls biogeochemical processes, nutrient and pollutant transport, catchment response functions, land-atmosphere exchange, and rainfall-runoff processes. In addition, the vadose zone as part of the critical zone provides important ecosystem services. Key research challenges include amongst others improving characterization of vadose zone properties, reducing uncertainty in quantifying vadose zone water fluxes including exchange with aquifers and surface waters and feedbacks within the soil-vegetation-atmosphere continuum. Guided by advanced sensor technologies, high-frequency observations and reanalysis, scientists are able to bridge scales and deduct processes at unprecedented resolutions for an in-depth more data-driven understanding of vadose zone processes.
In tandem with big data availability, new methods in machine learning and artificial intelligence may provide additional methodological capacity to understand the role of vadose zone, especially when tackling dynamic behavior of vadose zone properties as a result of changing frequency, duration and magnitude of drought and flood events.
We invite you to submit contributions from experimental, field and laboratory studies as well as synthetic and modeling studies from the pore to continental scales. Contributions to this session include soil hydrological processes, characterization of soil properties, soil biogeochemical processes, transport of pollutants, and studies on the soil-vegetation-atmosphere system. Presentations of novel, interdisciplinary approaches and techniques are also highly welcome.

Orals: Mon, 15 Apr | Room B

08:30–08:35
08:35–08:45
|
EGU24-2947
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On-site presentation
Gerrit H. de Rooij

Recent models of the unsaturated hydraulic conductivity curve (UHCC) are the sum of separate UHCCs for domains of capillary water, film water, and water vapor. A new theoretical framework for aggregating domain conductivities to a bulk soil UHCC reveals that this requires parallel domains. The same theory also generates arithmetic, harmonic, and geometric averages of the liquid-water conductivities, which can be arithmetically averaged with the vapor conductivity. However, current models for capillary and film conductivities are intrinsic, i.e., valid within their respective domain. The vapor conductivity is a bulk conductivity, i.e., it gives the conductivity of the gaseous domain as it manifests itself in the soil. Conversion relationships use the domain volume fractions as approximations of the as-yet unknown weighting factors to convert between intrinsic and bulk conductivities. This facilitates consistent averaging of domain conductivities. The fitted curves for the capillary and film water depend on the averaging (or adding) method. Hence, they are not strictly characteristic of their respective domains. Truly intrinsic domain conductivity functions may not exist, or are perhaps merely tools to arrive at a good fit of the UHCC of the bulk soil. Given these complications, a simpler junction model that joins a capillary and a film limb at a junction point offers an attractive alternative. 

How to cite: de Rooij, G. H.: The unsaturated soil hydraulic conductivity as a sum, an average, or a junction of domain conductivities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2947, https://doi.org/10.5194/egusphere-egu24-2947, 2024.

08:45–08:55
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EGU24-6425
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ECS
|
On-site presentation
Julian Schoch, Madlene Nussbaum, Lorenz Walthert, Andrea Carminati, and Peter Lehmann

Land surface models need information on soil hydraulic properties (SHP) that are often estimated using pedotransfer functions (PTFs). Due to a lack of calibration data, PTFs must be applied that were trained for regions and land use types outside the region of interest. In this study, we quantify the transferability of PTFs to new regions as function of mathematical complexity and number of covariates. For that purpose, we trained new PTFs for forest soils based on a dataset of 25 soil profiles from climatically moderate regions of Switzerland. In a second step, we tested the new and some existing PTFs in a drier and hotter Swiss region (Valais). Tests of transferability showed that increasing the mathematical complexity (from a linear model to a highly non-linear random forest model) was always beneficial for the predictive power in new regions. Increasing the number of covariates revealed a trade-off between improving the accuracy of the predicted soil water retention curve and reducing accuracy of the soil hydraulic conductivity. Interestingly, the use of environmental predictors (climate data) hampers transferability the most due to large climatic contrasts between the calibration and validation regions. These results suggest that transferability works better for PTFs using fewer predictors. We recommend the use of non-linear PTFs based on soil texture, soil density, and organic carbon content for optimal prediction accuracy in regions without training data. This work highlights that the models with the highest number of predictors are not optimal for achieving transferability and that reducing the number of predictors can be beneficial.

How to cite: Schoch, J., Nussbaum, M., Walthert, L., Carminati, A., and Lehmann, P.: Does model complexity of a pedotransfer function for soil hydraulic properties hamper its transferability?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6425, https://doi.org/10.5194/egusphere-egu24-6425, 2024.

08:55–09:05
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EGU24-20473
|
On-site presentation
Maria Clementina Caputo

Hydraulic Conductivity and Water Retention Functions of Porous Rock and Glacial Till Soil: Quasi-Steady Centrifuge versus Evaporation Methods

Maria Clementina Caputo1, Lorenzo De Carlo1, Antonietta Celeste Turturro1, Horst Herbert Gerke2

1CNR National Research Council, IRSA Water Research Institute, via Francesco De Blasio 5, 70132 Bari, Italy

2Research Area 1 “Landscape Functioning”, Leibniz-Centre for Agricultural Landscape Research (ZALF), Eberswalder Straße 84, D-15374 Müncheberg, Germany

 

 

Experimental laboratory measurements of the hydraulic conductivity and the water retention functions have a crucial role in describing the solid matrix-water dynamics. However, the direct determination of the hydraulic conductivity, K, as a function of the pressure head, h, is still difficult.  It is often estimated indirectly from the water retention curve, which relates the water content, θ, to h, or obtained by using pedotransfer functions or by field data of  pumping tests.

In this study the unsaturated hydraulic conductivity values of carbonate porous rocks and soil clods were measured by means of evaporation, Quasi-Steady Centrifuge (QSC) and double-membrane steady-through flow methods. Water retention curves were obtained by using the evaporation, QSC, suction table, Mercury Intrusion Porosimetry (MIP) and pressure chambers methods. Samples belonging to two rock lithotypes collected in southern Italy and to two soil clods coming from northeastern Germany were tested. The data were fitted to the unimodal and bimodal functions of van Genuchten and the Peters-Durner-Iden models by using the LABROS SoilView Analysis software. The bimodal functions better described the experimental data of both the studied rocks and soils.

The soil compaction during the centrifuge runs performed by applying the QSC method, corroborated by changed values of bulk density, porosity, tortuosity, and pore connectivity after the runs, confirms that this method is not suitable to non-rigid media.

The results confirm that the QSC method allows measuring the unsaturated hydraulic conductivity values for rock samples. The larger range of experimental hydraulic conductivity values helps to improve the fitting and obtain the more accurate of the hydraulic conductivity function to better describe the unsaturated rock-soil-water dynamics.

How to cite: Caputo, M. C.: Hydraulic Conductivity and Water Retention Functions of Porous Rock and Glacial Till Soil: Quasi-Steady Centrifuge versus Evaporation Methods, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20473, https://doi.org/10.5194/egusphere-egu24-20473, 2024.

09:05–09:15
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EGU24-4130
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On-site presentation
John R. Nimmo

Films, rivulets, snapping rivulets, sliding drops, slugs—many flow modes besides filled-tube, Poiseuille-type flow occur in macropores. Some of these fit reasonably into Darcian formulations and the analog of laminar viscous flow in water-filled tubes. But others do not. These exceptions may be the main reason for failures to predict the speed and travel distance of preferential flow.

A useful first step for an improved model of macropore flow is the classification of diverse flow modes into categories based on their intrapore boundary conditions. Within a flowing macropore, the gas-liquid and liquid-solid interfaces, with the effects of interfacial constraints such as surface tension and contact angles, determine the geometry of the flowing liquid phase and its controlling frictional influences. A classification scheme with four categories can account for the various flow modes that have been observed in lab and field experiments. This categorization helps to distinguish which flow modes are amenable to Darcian or Poiseuille-type representation and which are not. Some of the exceptions are approachable with wave or film-flow concepts as in several recently-developed models. Yet there are other flow modes that do not fit well in any of these models, and in some cases these may be the most important means of rapid and long-distance transport. Other sorts of physical processes may provide suitable analogs for these, for example free-fall concepts like initial acceleration, speed-dependent frictional forces, and terminal velocity. In any case, the diversity of macropore flow modes needs to be considered in the development of markedly improved models of preferential flow.

How to cite: Nimmo, J. R.: Diverse modes of macropore flow—How to include them in predictive models?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4130, https://doi.org/10.5194/egusphere-egu24-4130, 2024.

09:15–09:25
|
EGU24-4961
|
Virtual presentation
Characterization of wormhole dissolution in different fractal dimensionless fractures
(withdrawn)
Yutian Zhang, Jinfeng Xie, Fengqiao Wang, Yilei Gao, Bowen Ling, and Xiaoguang Wang
09:25–09:35
|
EGU24-3939
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On-site presentation
Quirijn de Jong van Lier

The SWAP model employs a finite difference numerical solution of the Richards equation, including root water uptake, to simulate the movement and predict the state of soil water and associated quantities in the vadose zone. The relation between hydraulic conductivity K, pressure head h, and water content θ can be described by parameters of the Van Genuchten-Mualem (VGM) relations, where the quality of these parameters determines the quality of the model output. We developed a stochastic procedure to evaluate the outputs of the SWAP model according to the uncertainty and correlations in the VGM parameters. Specific software was developed to (1) fit VGM parameters to observed retention and conductivity data to obtain values, standard errors, and correlations of transformed parameters (software HPFit); (2) generate p stochastic realizations of the VGM parameters using Cholesky decomposition (software StochHyProp), and (3) run the SWAP model with each of the p parameter realizations for specific scenarios, extracting simulation results (software RunSWAP), e.g., the simulated water balance components evaporation, transpiration, bottom flux, and runoff. The results from the last step yield the respective frequency distributions of the output values. Examples will show that the most commonly performed prediction using the average VGM parameter values does not always agree with the median of the stochastic realizations. The developed procedure allows the quantitative analysis of the uncertainty of SWAP model output, adding to the interpretation of the predictive power of hydrological models like SWAP.

How to cite: de Jong van Lier, Q.: Using the SWAP model for the stochastic analysis of hydraulic parameter uncertainty propagation in soil water balance components, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3939, https://doi.org/10.5194/egusphere-egu24-3939, 2024.

09:35–09:45
|
EGU24-22326
|
Virtual presentation
Nima Baghbani, Franziska Bucka, and Thomas Baumgartl

Incorporating Victorian brown coal (VBC) into the soil as a reliable amendment can markedly alter the hydraulic properties of the soil. A pivotal phenomenon influencing soil hydraulic parameters, particularly the soil permeability coefficient, is the extent of cracking and shrinkage observed during the drying process and consequent moisture loss. This study investigates the impact of incorporating VBC into clay and its influence on the two-dimensional cracking and shrinkage characteristics of the mixture. Various mixtures of brown coal from Latrobe valley in Victoria, Australia and clay, ranging from 2% to 20% brown coal content, were prepared and subjected to liquid limit and plastic limit tests. The samples were then readied for cracking and shrinkage assessments under liquid limit moisture conditions as an initial moisture content, featuring a sample diameter of 150 mm and a thickness of 10 mm. Results from the liquid limit tests demonstrated a decreasing trend in the liquid limit of the mixture with increasing brown coal content, registering values of 38.3%, 37.4%, 36.5%, 34.9%, and 32.9% for 0%, 2%, 5%, 10%, and 20% brown coal mixtures, respectively. Plastic limit tests indicated a 1.7% reduction, decreasing from 20.6% to 18%.9, with the addition of 20% brown coal. Furthermore, cracking and shrinkage tests revealed a substantial reduction in the cracking index (cracking intensity factor, CIF) of the mixture upon the addition of brown coal, reaching zero for mixtures containing 5%, 10%, and 20% brown coal after exposure to a 45℃ temperature for 30 hours. Additionally, the shrinkage index (shrinkage intensity factor, SIF) decreased from 15.4% for the clay soil sample to 14.9%, 14.6%, 13.9%, and 13.1% for the 2%, 5%, 10%, and 20% brown coal mixtures, respectively. This underscores the positive influence of brown coal on mitigating soil cracking and shrinkage, emphasizing its significance in soil science research.

How to cite: Baghbani, N., Bucka, F., and Baumgartl, T.: Soil management using lignite to improve soil cracking properties and performance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22326, https://doi.org/10.5194/egusphere-egu24-22326, 2024.

09:45–09:55
|
EGU24-4344
|
Virtual presentation
The strength and soil water characteristics for subsurface clays under low suction
(withdrawn)
Muawia Dafalla
09:55–10:05
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EGU24-7858
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On-site presentation
Peter Lehmann, Patrick Duddek, and Andrea Carminati

Despite its limited vertical extent, the thin soil layer provides essential functions for climate and ecosystems globally. For accurate large scale process description, land use models compute the water distribution in soils based on spatial domains with a width-to-thickness ratio of about 1000:1: a geometry as thin as a sheet of paper. Most models simulate the water flow in these ‘soil sheets’ by solving the Richardson-Richards equation in 1D, neglecting smaller scale structures and lateral flow, and implicitly making strong assumptions on the relations between water content, matric potential, hydraulic conductivity, and water flux. To quantify the accuracy of this conceptualization, we compare drainage simulations of wet soils for the 1D column simplification with the full 2D-and 3D geometry using the correct sheet-like size ratio. The role of different climates, soil types, and heterogeneities at smaller scale is analyzed. These simulations based on the full geometry provide guidelines for (i) the applicability of Richardson-Richards equation in land surface models and (ii) the development of appropriate averaging schemes of soil hydraulic properties in the 1D scenario.

How to cite: Lehmann, P., Duddek, P., and Carminati, A.: Water flow across the skin of the Earth – how badly are we doing?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7858, https://doi.org/10.5194/egusphere-egu24-7858, 2024.

Coffee break
10:45–10:50
10:50–11:00
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EGU24-20395
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ECS
|
On-site presentation
A dual-porosity extension of the Arya and Paris pedotransfer function for the hydraulic properties of structured soils
(withdrawn)
Shawkat Basel Mostafa Hassan, Giovanna Dragonetti, Alessandro Comegna, Nicola Lamaddalena, and Antonio Coppola
11:00–11:10
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EGU24-21584
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ECS
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On-site presentation
Frederik Graaf, Michael Bock, Olaf Conrad, and Robin Sur

Existing water balance assessments may lack precision due to overlooking the spatial variations in factors such as soil and topography while transferring the results from point modelling to a wider area. In cooperation with Bayer AG Crop Science Division and Hamburg University, within the DREAM (Digital Run-off Exposure Assessment and Management) project, a model is being developed which is temporally dynamic as well as spatially differentiated to provide a more nuanced and location-specific understanding of quantitative water dynamics. It is based on high resolution grid data and features a multi-layered soil water model, the goal of which is to depict volumes of water in different soil layers. It is to be employed in an agricultural context and serve as a toolbox of possible runoff reduction measures for plant protection products.

Since risk management is a highly localized undertaking, the model operates at a field- or sub-field-level with a spatial resolution of up to one meter. The temporal resolution of simulation steps is variable; from one hour to a day. The necessary input data – that being a digital terrain model, information about the vegetation as well as soil and weather data – create conditions specific to the site.

It is embedded in the open source geoinformation system (GIS) SAGA. The modular approach allows for flexible development and changes on short notice. The model includes an algorithm that determines soil water movement, incorporating the groundwater layer as the model’s lower boundary. To achieve this, an expanded bucket model for soil water movement, based on the works of Glugla, is used. Should the infiltration capacity of the soil - calculated via the Green-Ampt-Method - be surpassed, runoff occurs. In this case, the model possesses the ability to depict runoff and its flow paths through the terrain, along with the respective volumes and flow velocity based on Gauckler-Manning-Strickler.

While the current focus lies on the movement of water, the model is designed for gradual expansion and improvement, allowing for future considerations such as the tracking of solutes moving into larger depths or even into groundwater.

How to cite: Graaf, F., Bock, M., Conrad, O., and Sur, R.: Design of a spatially differentiated water balance modelling tool, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21584, https://doi.org/10.5194/egusphere-egu24-21584, 2024.

11:10–11:20
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EGU24-16238
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On-site presentation
Salohy Nantenaina Andriatahiana, Idrissou Sinabarigui, Nathalie Courtois, Jean-Pierre Vandervaere, and Jean-Martial Cohard

Pollutant transfers in the critical zone is an issue for decades both because of complex physico-chemical interactions in the porous media and because of the emergence of new materials/molecules rejected in the environment for which rules are not ready. The study presented here is part of a research project which aimed to predict transfers and residence time of pollutants in the critical zone including the Unsaturated Zone (UZ), and in aquifers on the CEA Cadarache site (France). This site benefits from a large instrumentation for decades to survey both the water dynamic and quality in the aquifers below the industrial facilities. One of the remaining challenges is to study the distributed recharge in the UZ. In situ measurements of saturated hydraulic conductivity Ks are often time-consuming, but also costly to implement at a catchment scale. To overcome this difficulty, an approach using Pedotransfer Functions (PTFs) is possible in order to spatialize this parameter of the UZ (Nasta et al., 2021; Weihermüller et al., 2021). The main objective of the study is to evaluate a spatialization strategy of Ks values using PTFs calibrated from an intensive in situ measurement campaign.

A total of 48 measurement points were selected on the study site, covering an area of around 900 hectares. The points were chosen to represent the different types of geological formations at the outcrop as well as the different types of land cover on the site. For all those locations, in situ hydraulic conductivity measurements were carried out with a disc infiltrometer, using the multi-potential method (Vandervaere, 1995), together with physico-chemical analyses of the surface soils. The results obtained show that for most of the measurement points, a fairly clear break in the slope of the exponential function K(h) appears for potentials h around -30 / -20 mm. The estimate of the value of Ks is chosen as being the value of K(h) obtained for the last value of potential h = - 5 mm, considering that saturation has been reached. On site, Ks varies from 20 to 410 mm/h.

Several PTFs for estimating Ks were selected (Rawls & Brakensiek, 1985, Wösten et al., 1999, Weynants et al., 2009, Szabó et al., 2021, Rosetta (Schaap et al., 2001; Zhang & Schaap, 2017)). The study will help us to identify some geological or land cover drivers for Ks ranges and to select which PTFs are able to represent such a variability.

How to cite: Andriatahiana, S. N., Sinabarigui, I., Courtois, N., Vandervaere, J.-P., and Cohard, J.-M.: Saturated hydraulic conductivity spatialization strategy to model recharge and hydrogeological transfers on an industrial site in France, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16238, https://doi.org/10.5194/egusphere-egu24-16238, 2024.

11:20–11:30
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EGU24-19703
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On-site presentation
Conrad Jackisch, Sophie Marie Stephan, Jens Tronicke, and Niklas Allroggen

Infiltration is a central concern in soil physics. The advective and diffusive redistribution of event water depends on various factors such as initial wetting, the establishment of film connectivity, and capillary gradients and hydraulic conductivity. Non-uniform infiltration patterns are prevalent. However, direct infiltration measurements do not account for this reality and tracer experiments require a destruction of the experimental plot. We developed a data acquisition strategy based on time-lapse 3D ground-penetrating radar (GPR) to monitor fast and small-scale subsurface flow processes during irrigation in a non-invasive manner.

The technique combines an irrigation pad (1 m2 drip irrigation to simulate moderate, non-erosive rain events) with a GPR measurement platform (manually driven two-channel GPR antenna array with positioning guides). We will present a systematic field experiment consisting of two recurrent irrigations (40 mm/2 h, 1 irrigation per day) and a respective replicate. For evaluation, the GPR measurements were sidelined with soil moisture measurements (TDR profile) and tracer applications (dye and salt). Our data show that the achieved high resolution of less than 5 cm in space and 10 minutes in time makes it possible to monitor and quantify infiltration processes in their spatial and temporal non-uniformity.

The experiment supports the hypothesis from earlier experiments at various sites: Non-uniform infiltration patterns and dynamically connected flow-fields are highly heterogeneous but share stochastic features, such as distribution, randomness, and skewness. Our approach opens new options for repeated, spatially resolved infiltration measurements and theory development for soil hydrology and land surface models.

How to cite: Jackisch, C., Stephan, S. M., Tronicke, J., and Allroggen, N.: Infiltration as dynamic non-uniform stochastic flow field – repeatable, high-resolution 4D GPR measurements at the plot scale, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19703, https://doi.org/10.5194/egusphere-egu24-19703, 2024.

11:30–11:40
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EGU24-7939
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ECS
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On-site presentation
Alexander Sternagel, Ashish Dinesh Rajyaguru, Luca Trevisan, Ralf Loritz, Brian Berkowitz, and Erwin Zehe

We applied neutron imaging techniques to unveil pore scale flow processes occurring during desaturation of a homogeneous, saturated sand pack. For this purpose, we used a small glass flow cell (2 cm x 2 cm x 0.1 cm) filled with pure, artificial S250 quartz sand. The pore space of the sand was initially fully saturated with double distilled water (DDW). The saturated flow cell was subjected to a series of suction phases with increasing suction tensions to extract water via a bottom outlet, controlled by a vacuum pump. In the first phase, a tension of 0.016 MPa (low suction) was applied for 248 min, followed by 1.14 MPa (mid suction) for 227 min, and finally, 10 MPa (high suction) for 397 min. Throughout the entire duration of the experiment, the flow cell was continuously exposed to neutrons. A back-end detector collected the neutron beams passing through the different matters (sand, water, air) contained in the flow cell and generated snapshot images of the internal pore structure and the water distribution with a pixel resolution of 5 µm at one-minute intervals.

The resulting images revealed that water did not redistribute homogeneously during the desaturation of the flow cell, over dimensions of a few millimeters. Despite using “perfectly homogeneous” sand under initially fully water-saturated, controlled conditions, heterogeneous patterns of stable water pockets were observed inside the pore space of the sand, where water became immobilized.

These experiments demonstrate that truly homogeneous flow does not occur even under controlled laboratory conditions in a “perfectly homogeneous” porous medium.

Subsequent simulations of the experiments with common Darcy-Richards models showed that the macroscopic 1D desaturation time series of the flow cell could be realistically depicted. However, even after parameter calibration and the manual addition of heterogeneity, the microscopic, heterogeneous 2D distribution of water observed inside the flow cell could not be reproduced.

This highlights limitations on the applicability of Darcy-Richards models, which may be effective at a macroscopic level but simultaneously fail to represent accurately the internal dynamics of the system. This insight is crucial for the application of Darcy-Richards models and the interpretation of their results.

How to cite: Sternagel, A., Rajyaguru, A. D., Trevisan, L., Loritz, R., Berkowitz, B., and Zehe, E.: Neutron imaging unveils heterogeneous flow patterns in homogeneous porous media and limitations of Darcy-Richards models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7939, https://doi.org/10.5194/egusphere-egu24-7939, 2024.

11:40–11:50
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EGU24-18554
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ECS
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On-site presentation
Einar Emil Låker, Attila Nemes, and Daniel Hirmas

Saturated hydraulic conductivity (Ksat) is one of the most fundamental parameters in soil hydrology. It governs the rate of saturated flow through porous media and functions as a scaling factor for unsaturated flow. Knowledge of Ksat is key to understanding the movement of water in soils, transport and recharge of groundwater, suspended and dissolved transport in soils, and soil-air water exchange. In hydrology and climate modeling Ksat is often estimated through pedotransfer functions. A large effort has been committed to the development of these models, using an array of differing algorithms and methods. However, estimating Ksat has been somewhat troublesome, since the commonly measured soil properties, such as soil texture, bulk density and organic matter content, used as predictor variables in PTFs do not explain Ksat variation well. Instead, Ksat is largely controlled by pore-network characteristics especially in highly-structured soils. Using an extended, methodologically homogeneous dataset of commonly measured soil physical properties, 3-D X-ray computed tomography imaged pore-network parameters, and quasi-continuous particle-size measurements using the Integral Suspension Pressure method, we assess the benefits of using combined soil textural and structural information on the estimation of Ksat. Using this dataset, we have built models that estimate Ksat using a boosted random forest algorithm (XGboost) and used explanatory model analysis to tune and evaluate the models. Three input data scenarios included (i) basic soil inputs only (ii) imaged pore metrics only, and (iii) their combination. Using or adding imaged pore metrics as inputs greatly improved the Ksat estimations that were reflected, for example, by the respective coefficients of determination, evaluated using a cross-validation scheme (R2 = -0.05/0.60/0.58 for the three input scenarios respectively). 3-D imaging of soil and the subsequent characterization of its pore-space may serve multiple research purposes, but such data are still not routinely collected due to cost of measurement and general lack of access to equipment. Our study confirms, however, that when collecting such metrics will become economically feasible through e.g. better automation of image processing using tools like SoilJ, having those metrics will show great potential towards improving the estimation of the soil’s water transport properties. 

How to cite: Låker, E. E., Nemes, A., and Hirmas, D.: Can 3-D X-Ray tomography imaging improve the estimation of saturated hydraulic conductivity of soils?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18554, https://doi.org/10.5194/egusphere-egu24-18554, 2024.

11:50–12:00
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EGU24-10596
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ECS
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On-site presentation
Sonia Akter, Johan Alexander Huisman, and Heye Reemt Bogena

Continuous monitoring of root-zone soil moisture status is important to ensure the effective management of water resources for agricultural production, and to improve our understanding of land-atmosphere interactions in a changing climate. Utilizing gamma radiation to monitor soil moisture at the field scale is an emerging non-invasive technique that can also bridge the gap between point and remote sensing measurements. The measurement principle relies on the increased attenuation of gamma radiation emitted from soil with increasing soil moisture content. In a previous study, we successfully obtained soil moisture estimates from low-cost environmental gamma radiation (EGR) detectors. However, since EGR detectors provide the bulk response to gamma radiation over a wide energy range (0 to 3000 keV), EGR signals are influenced by several confounding factors, e.g., skyshine radiation, atmospheric and soil radon variability. To what extent these confounding factors deteriorate the accuracy of soil moisture estimates obtained with EGR is still not fully understood. Therefore, the aim of this study is to compare EGR measurements with K-40 gamma radiation (at 1460 keV) measurements that are much less influenced by these confounding factors. For this, two different kinds of gamma radiation detectors were installed close to each other at an agricultural field in Selhausen, Germany: an EGR detector based on a G-M counter tube (MIRA, ENVINET GmbH) and a spectroscopic scintillation-based detector (SARA, ENVINET GmbH). The field was also equipped with in-situ soil moisture sensors to measure reference soil moisture and a climate station to measure meteorological parameters. The EGR measurements were corrected for atmospheric radon-washout during precipitation events and the contributions of meteorologically influenced secondary cosmic radiation were also eliminated. In case of the spectroscopic measurements, no further corrections were applied as the analysis was only focused on the K-40 energy window. Both sets of gamma radiation measurements were related to reference soil moisture using a functional relationship derived from theory. We found that daily soil moisture can be predicted more accurately from K-40 gamma radiation (RMSE 4 vol.%) than from EGR (RMSE 6 vol.%). Regardless of the higher prediction uncertainty obtained due to the influence of the confounding factors at low energy, the long-term availability of ERG data, e.g., in Europe via EURDEP, makes it interesting for continental scale analysis of soil moisture. 

How to cite: Akter, S., Huisman, J. A., and Bogena, H. R.: Comparing the accuracy of soil moisture estimation derived from environmental and spectroscopic gamma radiation measurements , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10596, https://doi.org/10.5194/egusphere-egu24-10596, 2024.

12:00–12:10
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EGU24-11928
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ECS
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On-site presentation
Nedal Aqel, Andrea Carminati, and Peter Lehmann

The matric potential plays a pivotal role in understanding of water movement, plant water availability, and mechanical stability. In lack of direct measurements, the matric potential dynamics must be deduced from soil water content values, using the soil water retention curve. This approach is of particular importance at larger scales where only the water content (but not the potential) can be deduced from satellite data. However, because the relationship between water content and matric potential in natural field soils is highly ambiguous, not unique and dynamic, the prediction of matric potential from water content data is a big challenge. This ambiguity is related to different structures controlling drainage and wetting, dynamic effects, and seasonal changes of structures controlling the water distribution. In this study we present an autoencoder neural network as a new approach to analyze the soil moisture dynamics and to predict matric potential from water content data. The autoencoder compresses the water content time series into a site-specific feature (denoted as autoencoder value, AUV) that is representative of the underlying soil moisture dynamics. The AUV can then be used as predictor of the matric potential and the highly hysteretic soil water retention curve. The approach was tested successfully for nine soil profiles in the region of Solothurn (Switzerland). Three sites were chosen to establish the connection between AUV and the ambiguous soil water retention curve using a deep neural network, that was then applied to predict the matric potential dynamics of the other six sites. This method offers the potential to (i) deduce matric potential dynamics by relying solely on soil water content measurements (including satellite data), even when strong seasonal effects challenge standard methods, and (ii) serves as a warning system for changes in soil properties and in the intricate relationship between soil water content and matric potential dynamics.

How to cite: Aqel, N., Carminati, A., and Lehmann, P.: The dynamics of field soil water retention curves predicted by autoencoder neural network, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11928, https://doi.org/10.5194/egusphere-egu24-11928, 2024.

12:10–12:20
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EGU24-12291
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ECS
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On-site presentation
Fernando Gimeno, Mauricio Zambrano-Bigiarini, Mauricio Galleguillos, and Rodrigo Marinao

Soil data is a crucial component for hydrological models operating at the catchment scale, such as the Soil and Water Assessment Tool (SWAT). Nevertheless, the reliability of these models is heavily contingent upon the quality and spatial resolution of the soil information employed. This study addresses the pressing need for robust soil data in SWAT modeling by evaluating various soil mapping techniques.

The first objective was to prove different mapping techniques, such as textural class combination and clustering approach using soil grid data to have different soil maps. The performance of those maps, together with WRB, WSR, Zobler, HWSD v2.0 and DSOLMAPS, was evaluated to improve the accuracy and reliability of the SWAT hydrological model. To achieve this, we conduct a comprehensive investigation involving multi-objective calibration, utilizing both flow data and soil moisture data to calibrate the model. Finally we incorporate a  pedotransfer function to include the landcover effect on Saturated Hydraulic Conductivity to improve the reliability of soil hydrological processes in the SWAT model.

The study area, situated within the Cauquenes River Catchment, presents a complex hydrological system characterized by substantial spatial heterogeneity in soil properties. The soil mapping techniques under evaluation encompass traditional soil survey data integrated with remotely sensed soil information and machine learning-based soil mapping methodologies. These methods are compared in their ability to enhance the SWAT model's representation of the catchment's hydrological dynamics.

In the case of the kmeans clustering approach the results of soil clusters are equivalent to soil units. A number of clusters from 3 to 100 were evaluated with the lowest DB index. Clusters from 3 to 16 presented an optimal range. The SWAT model calibration was performed under multi-objective evaluation, with kmeans soil cluster and DSoilMaps with better result for daily simulations.

The work to correct the application of soil data, including in situ observation, satellite data and machine learning approach, provides a valuable approach to improve the calibration and validation processes of hydrological models in semi-arid regions, important for cacthment management and decision making processes, and to correctly assess the impacts of land use changes, climate variability and extreme events on water resources. 

How to cite: Gimeno, F., Zambrano-Bigiarini, M., Galleguillos, M., and Marinao, R.: Evaluation of Soil Mapping Methods for SWAT Hydrological Modeling through Multi-Objective Calibration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12291, https://doi.org/10.5194/egusphere-egu24-12291, 2024.

12:20–12:30
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EGU24-13980
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ECS
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On-site presentation
Lin Liu, Xiaoting Xie, Yili Lu, and Tusheng Ren

The location of dry layer interface (LDI), which varies during soi drying process, is a key parameter for characterizing soil water evaporation process. Recently the heat pulse (HP) technique has been applied to estimate the LDI indirectly. However, errors may occur with the HP method when analytical solutions are used because of soil heterogeneity across the measurement plane, especially when a heterogeneous interface lies between the two probes. In this study, we propose a numerical inversion-based heat pulse method for estimating the LDI under five configurations. The inputs are thermal properties of dry and wet soils, and the temperature rise-by-time curves at two locations from the heat source. The heat source was positioned at different distances from the LDI. The inversion method was evaluated with temperature rise-by-time curves from 17 scenarios obtained from numerical simulation and 14 scenarios obtained from laboratory measurements. Results demonstrated that the new approach produced reasonable LDI estimates within the range of 0.1 to 5 cm to the soil surface, with relative errors (REs) less than 0.30, except for the situation that the LDI was close to the heat source. The proposed method has significant implications in groundwater management and modeling hydrological processes in unsaturated soils.

How to cite: Liu, L., Xie, X., Lu, Y., and Ren, T.: Locating the dry layer interface during soil water evaporation by using numerical inversion-based heat pulse method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13980, https://doi.org/10.5194/egusphere-egu24-13980, 2024.

Orals: Tue, 16 Apr | Room B

08:30–08:35
08:35–08:45
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EGU24-18945
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ECS
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On-site presentation
Vishnu U Krishnan, Noemi Vergopolan, Indu Jayaluxmi, and Karthikeyan Lanka

Soil moisture is an important state variable with high spatiotemporal variability depending on land and climate variables. The importance of various physical controls on soil moisture varies depending on the scale and extent of the study. At a fine scale, soil properties are proven to be critical in defining spatiotemporal variability of soil moisture. In the context of agricultural applications in India, soil moisture estimates at the farm scale (finer spatial resolution) over various root depths are essential.  Traditional Land Surface Models (LSMs) are limited to large spatial scales (in the order of tens of kilometers). They have been designed for synergistic coupling with Earth system models. Besides, they do not account for the vertical heterogeneity of soil. LSMs, including Noah-MP, use a lookup table to obtain soil properties corresponding to soil texture while assuming vertically homogeneous soil texture. Recent studies proved that accounting for vertical heterogeneity in the soil using state-of-art soil maps and pedotransfer functions in LSM can significantly improve the surface soil moisture estimations. However, the effects of incorporating vertical heterogeneity in soil properties on deeper layer soil moisture simulations are yet to be explored. Considering the importance of farm scale root water uptake processes, understanding soil moisture heterogeneity at deeper layers is essential. In this context, the present study hypothesizes that a hyperresolution LSM, which accounts for subgrid spatial heterogeneity while maintaining soil heterogeneity between layers, can improve the characterization of rootzone soil moisture. 

In this work, we used HydroBlocks, a semi-distributed hyper-resolution LSM, which uses Noah-MP at its core, and the concept of Hydrologic Response Units (HRU) to simulate the land surface variables. The analysis is carried out for the first time in India over the Upper Bhima Basin, for the year 2020. Initially, we investigated the benefit of vertical heterogeneity in soil properties to simulate soil moisture at five different layers till one meter deep using HydroBlocks. We used SoilGrids data for different layers to calculate soil hydraulic properties using PTFs and feed them as inputs in the HydroBlocks model. We compare HydroBlocks surface and rootzone soil moisture to existing reanalysis and satellite products, including GLEAM, ERA5-Land, SMAP-L3, and SMAP L4 statistically in terms of bias, ubRMSE and R2. Further, an intercomparison of surface and rootzone soil moisture simulations is made between the two cases of Hydroblocks model, first with vertically homogeneous soil properties, and second, with vertically heterogeneous soil properties. The objective of this step is to emphasize the role of vertically heterogeneous soil layers in a hyper-resolution LSM towards addressing the spatiotemporal variability of soil moisture. Finally, a soil parameter sensitivity analysis (using Sobol technique) is carried out using HydroBlocks for five soil layers (up to 1 meter depth), for the first time, to assess the influence of eight soil textural parameters such as wilting point, porosity, pose size distribution, and likewise, on soil moisture simulations. In this process, we also assessed the seasonal variability of parameter sensitivity.

How to cite: U Krishnan, V., Vergopolan, N., Jayaluxmi, I., and Lanka, K.: Examining the benefits and sensitivity of vertically heterogeneous hyper resolution land surface model towards simulating a farm scale soil moisture profile in Upper Bhima Basin, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18945, https://doi.org/10.5194/egusphere-egu24-18945, 2024.

08:45–08:55
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EGU24-12041
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On-site presentation
Daniel Camilo Roman Quintero, Emilia Damiano, Lucio Olivares, and Roberto Greco

The loose, stratified composition of pyroclastic soil covers typically consists of layers of air-fall ashes and pumices. When these deposits are resting on steep slopes, they pose a significant geohazard due to slope instabilities. This scenario is evident in the carbonate massifs covered by pyroclastic soils in Campania (southern Italy), an extensive area of about 400 km2 prone to landslides. In these porous deposits, the soil suction in unsaturated conditions plays a crucial role in enhancing the slope stability by providing additional shear strength.

This study aims to present a comprehensive overview of the hydraulic and shear strength characteristics observed in different layers of pyroclastic ashes across various sites in the Campania study area. By gathering datasets from previous studies and introducing new experimental data, the relationship between soil index, hydraulic properties and the shear strength in unsaturated conditions is examined.

The findings highlight notable differences in hydraulic properties of soils originating from the same location but belonging to different layers: ashes from intermediate layers within the soil profile, where failure surface usually occurs; weathered ashes in direct contact with the carbonate bedrock, responsible of water exchange with deeper systems. The water retention curves of intermediate ashes exhibit air entry values at approximately 4 kPa, while those in contact with the bedrock show values around 25 kPa. Conversely, soils from the same layer but from different sites exhibit relatively similar hydraulic characteristics. For example, intermediate ashes from the same layer typically display air entry values varying between 0.5 kPa and 4 kPa. The same behavior also appears regarding the influence of soil suction on the shear strength of the investigated materials, which can be estimated directly from the water retention curves.

How to cite: Roman Quintero, D. C., Damiano, E., Olivares, L., and Greco, R.: Overview of water retention and suction stress properties of layered pyroclastic ashes in landslide prone areas of Campania, southern Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12041, https://doi.org/10.5194/egusphere-egu24-12041, 2024.

08:55–09:05
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EGU24-12832
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ECS
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On-site presentation
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Gersende Fernandes, Maria Burguet Marimon, Maria Paz Salazar, Elisa Marras, Ilenia Murgia, Konstantinos Kaffas, Filippo Giadrossich, Ryan D. Stewart, Majdi R. Abou Najm, Alessandro Comegna, Laurent Lassabatère, Daniele Penna, Christian Massari, and Simone Di Prima

Incident gross precipitation is divided by tree canopies into three main parts: i) intercepted rainfall, which evaporates directly from the canopies, ii) throughfall, which reaches the soil surface after passing through the canopies, and iii) stemflow, which is concentrated from the canopies to the stems. Stemflow tends to infiltrate preferentially around the base of the stem, and once belowground, is channeled by tree roots.

The objective of this research was to investigate the contribution of stemflow and throughflow to subsurface water dynamics in a hillslope forested with beech trees. The experimental activities were carried out in a 10 x 10 m plot located in the Lecciona catchment of the Appennine Mountains, Central Italy.  Stemflow was collected from seven beech trees located within the plot. Stemflow and throughfall were sequentially and then simultaneously induced using controlled water applications. Time-lapse ground-penetrating radar (GPR) surveys were conducted under each line of trees. Overland flow and subsurface runoff were collected with V-shaped gutters positioned at the bottom of the trees and at the downhill plot edge.

Stemflow infiltration rates were calculated by a mass balance, i.e., subtracting the collected overland flow from the injected volume and then dividing by the stem basal area and the time of steady infiltration. Mean values for each tree and for the entire plot, the latter considering the throughfall experiments, were approximately 1000 mm/h. The GPR data enabled the detection of active preferential flow paths, assessment of hillslope connectivity, and estimation of flow velocities. GPR gave relevant information in the flow pathways in the soils, the effects of root systems and its combination with matrix flow.

This experiment represents a straightforward, replicable, and non-invasive method for characterizing the role of trees in water runoff and infiltration at the hillslope spatial scale, and more broadly, in understanding how forested hillslope respond to rainstorms.

How to cite: Fernandes, G., Burguet Marimon, M., Paz Salazar, M., Marras, E., Murgia, I., Kaffas, K., Giadrossich, F., D. Stewart, R., R. Abou Najm, M., Comegna, A., Lassabatère, L., Penna, D., Massari, C., and Di Prima, S.: Tree influence on water dynamics in sloped forest soils: insights from stemflow and throughflow experiments and time-lapse ground-penetrating radar monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12832, https://doi.org/10.5194/egusphere-egu24-12832, 2024.

09:05–09:15
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EGU24-14516
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ECS
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On-site presentation
Liantao Niu and Xiaoxu Jia

Extensive cropland-to-orchard transition alters water flow and nitrate transport in the vadose zone (VZ) of the Earth’s Critical Zone (CZ), which may impact groundwater recharge and threaten future water quality from intensive nitrogen fertilizer application. Understanding the regional unsaturated water and nitrate fluxes and travel times in the deep VZ is crucial for the sustainable management of the groundwater system. Here, a regional-scale model was developed to estimate the recharge and nitrate transport in the cultivated loess CZ of China’s Guanzhong Plain (CGP), where cropland-to-orchard transition has been extensively promoted in the past few decades. Besides, uncertainties and sensitivities in estimated fluxes of water and nitrate induced by variations in soil hydraulic parameters (SHPs) were evaluated. A comparison between model simulations and observations at 12 sites exhibits good simulation performance. Comparing the measured SHPs, SHPs from Rosetta and Global SHPs products introduced 86.28% and 48.94% uncertainties in the simulation of nitrate leaching fluxes from cropland and orchard, respectively, as well as 44.76% uncertainties in the simulation of groundwater recharge fluxes from the orchard. Application over the CGP based on measured SHPs indicates that the central and eastern CGP were the hotspots for groundwater nitrate contamination. By comparing traditional cropland and orchard scenarios, simulations reveal that cropland-to-orchard transition results in a 39.3-fold increase in nitrate leaching fluxes and a 9.8% decrease in groundwater recharge fluxes. Modeled nitrate travel times through the deep VZ range between decades and centuries under both land use scenarios; however, the cropland-to-orchard transition would extend the time (~22.4 years) it takes for nitrate to reach the aquifer. Although cropland-to-orchard transition delays nitrate transport to the aquifer, the increased nitrate leaching flux will increase the risk of nitrate groundwater pollution, especially in areas with shallow VZs and coarse soil texture. This study provides valuable information for assessing the future vulnerability of groundwater resources under agricultural land use and management changes in the cultivated loess CZ.

How to cite: Niu, L. and Jia, X.: Future Orchard Expansion May Decrease Groundwater Recharge and Increase Nitrate Contamination in An Intensively Cultivated Loess Critical Zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14516, https://doi.org/10.5194/egusphere-egu24-14516, 2024.

09:15–09:25
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EGU24-13600
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On-site presentation
Zheng Wang, Chi Zhang, Yaning Zhang, and Bingxi Li

Frost weathering is considered the primary cause of erosion in periglacial environments. This process is initiated by the freezing of water within rock pores and its subsequent expansion, which generates substantial forces leading to the physical fragmentation and disintegration of the rock structure. To detail the mechanism and predict the patterns of rock fracturing, this study has developed a specialized numerical model. In previous study, researchers typically studied the mechanical failure of rocks via macroscopic numerical methods. However, these methods often face limitations in depicting mesoscale forces, particularly in the context of multiphase flow processes of water migration. Moreover, the influences of various hydrothermal conditions on the mechanical behavior of rocks are frequently overlooked. In this study, a coupled lattice Boltzmann model (LBM) was developed to simulate the freezing process in rocks. The porous structure with complexity and disorder was generated by using a stochastic growth method, and then the Shan-Chen multi-phase model and enthalpy-based phase change model were coupled by introducing a freezing interface force to describe the variation of phase interface. By utilizing the developed model, the ice growth process in rock pores can be well depicted under porous conditions characterized by varying contact angles, porosities, and specific surface areas. Building on this foundation, our work advances the understanding of the complex interaction between thermal dynamics and mechanical processes in periglacial environments, shedding light on the mechanisms of frost weathering and the predictive modeling of rock fracture patterns under varying hydrothermal conditions.

How to cite: Wang, Z., Zhang, C., Zhang, Y., and Li, B.: A hydrothermal model for unsaturated frozen rocks based on lattice Boltzmann method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13600, https://doi.org/10.5194/egusphere-egu24-13600, 2024.

09:25–09:35
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EGU24-3493
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ECS
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On-site presentation
Shahad Al-Yaqoubi, Ali Al-Maktoumi, Anvar Kacimov, Osman Abdalla, and Said Al-Ismaily

The continuous and frequent occurrence of the Shallow Water Table (SWT) in urban regions aggravates the severity of geotechnical and environmental problems. Exploring possible measures that effectively reduce the negative impact of SWT in urban aquifers is of extreme importance. This research investigated the effectiveness of bioengineering techniques in lowering SWT in the framework of hydropedological factors (soil structure in the vadose zone, where most pore water fluxes take place). The methodology includes physical models (sand tank experiments) and field-scale studies. A total of nine sand tanks were utilized, segmented into three distinct groups, to investigate the reduction of the water table through different mechanisms: (1) evapotranspiration drawdown by soil water uptake by the roots of vegetation (specifically Reeds), (2) evaporation by bare homogeneous topsoil, and (3) evaporative “soil siphoning” in tanks that were made as “smart composites” with a fine-textured vertical “moisture chimney”. The dynamics of SWT were monitored over 6 months (March–September 2023). Each tank measures 100 cm in length, 70 cm in height, and 15 cm in width. All tanks were packed with two horizontal soil layers (sand and clay) to simulate a perched aquifer, common prototypes of which were explored in Muscat, Oman. In the siphoning experiment, a small trench was made and packed with silt loam soil. This trench extended the entire thickness of the aquifer to enhance capillarity and, hence, evaporation. Analysis of the results showed that the drawdown of the water table ranged from 75% to 300% (winter to summer seasons) in the tanks containing plants (Reeds) compared with the control tanks. In addition, the SWT in the tanks with “soil siphons” was reduced in the range of 22%-46% compared with the control tanks. Another experiment with Reeds was conducted on a larger field scale using Concrete Agricultural Basins (CABs) with dimensions of 1000 cm length, 200 cm width, and 60 cm depth. The experiment spanned three months (June-September 2023) and aimed to investigate the impact of Reeds on SWT levels in larger-scale 3D pore water dynamics (in sand tank experiments flows were 2D). Overall, the large-scale experiment showed that over the three months, the evapotranspiration from Reeds reduced the water level by 16.7%, 66.7%, and 116.7% more than evaporation from bare soil during the first, second, and third months, respectively.

This investigation highlights the significant influence of bioengineering through phreatophytic Reeds, seasonal variations of weather conditions, and the hydropedology of the root zone on checking the SWT levels. The influence of fine-textured soil lenses, strata, and engineered soil siphons in controlling water levels was studied. While the presence of Reeds plays a crucial role in influencing water levels, seasonal fluctuations, usually modeled by ET0-ETc, also contribute, with drastic differences between summer and winter. The investigated drainage techniques are ecologically and environmentally benign: no electricity or fuel is used for the reduction of waterlogging because only soil capillarity and solar energy maintain the processes of evaporation and transpiration; the Reeds’ biomass, accumulated during the ecoengineering process, additionally intercepts and sequesters CO2.

How to cite: Al-Yaqoubi, S., Al-Maktoumi, A., Kacimov, A., Abdalla, O., and Al-Ismaily, S.: Investigating the feasibility of Bioengineering and Hydropedological techniques in controlling shallow water table problem in urban areas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3493, https://doi.org/10.5194/egusphere-egu24-3493, 2024.

09:35–09:45
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EGU24-2584
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On-site presentation
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Min Li and Guangjie Chen

Deep-rooted vegetation transpires a considerable amount of deep soil water with different ages in the unsaturated zone. However, the tradeoffs between new water of transpiration (temporally originating from post-planting precipitation) and old water of transpiration (temporally originating from pre-planting precipitation) across the vegetation lifespan are poorly understood. In this study, we collected soil samples from beyond 28 m soil depth on the Loess Plateau of China to investigate the influence of deep-rooted vegetation on the age of soil water and analyze the proportion of new and old water of transpiration in the unsaturated zone under grassland, 22-year-old apple orchard, and 17-year-old peach orchard. Water isotopes (2H, 18O, and 3H), solutes (chloride, nitrate, sulfate), and soil water content were used to identify the critical water ages in the unsaturated zone (one-year water age, water age corresponding to stand age, and the maximum water age of transpiration), and to determine soil water deficit, soil evaporation loss fraction, and potential groundwater recharge. The results showed that soil water mainly moved as piston flow in these soil profiles, and deep soil water largely came from heavy precipitation. Deep-rooted vegetation restrained new pore water velocity and potential groundwater recharge. New pore water velocity declined from 0.40 m yr-1 to 0.14 m yr-1 and 0.34 m yr-1 for apple and peach, respectively. Deep-rooted vegetation decreased groundwater recharge by 9.46 % for apple and 7.04 % for peach, compared to grassland. Over the vegetation lifespan, annual average transpiration was 500.56 mm yr-1 and 468.89 mm yr-1 with maximum water age of 63 years and 45 years for apple and peach, respectively. The transpiration of deep-rooted vegetation mainly used new water (94.97 % for apple and 97.47 % for peach). The total old water of transpiration was 553 mm for apple and 209 mm for peach. Our results identify the temporal sources of vegetation water use, offering new insights into the transpiration process of deep-rooted vegetation.

How to cite: Li, M. and Chen, G.: Quantitative partitioning of temporal origin of transpiration into pre- and post-plantation under deep-rooted vegetation on the Loess Plateau of China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2584, https://doi.org/10.5194/egusphere-egu24-2584, 2024.

09:45–09:55
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EGU24-1708
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ECS
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On-site presentation
Ziv Moreno, Amir Paster, and Tamir Kamai

Drywell infiltration is a common approach to recharge groundwater and reduce load from drainage systems. Due to rapid acceleration in urban developments, as well as climate change that predicts an increase in frequencies and magnitude of extreme precipitation events in the Mediterranean area, it is critical to predict the drywell infiltration capacity, i.e., its response to anticipated precipitation events. The infiltration capacity of a drywell is mainly determined by the geometrical parameters, i.e., diameter and depth, and the soil hydraulic parameters, i.e., hydraulic conductivity, porosity, and water retention. Predictions of drywell infiltration capacity are commonly conducted using models that solve the unsaturated flow in the subsurface using complex and costly numerical schemes. This work proposes a different approach based on a semi-analytical model that relies on a sharp interface wetting front assumption. The proposed model can predict the water levels in the well and the subsurface wetting front location during and after an infiltration event. The semi-analytical model was tested and compared with numerical simulations of Richards' equation and with data from a field experiment and proved to be sufficiently accurate. The typical run times of the semi-analytical model are smaller than 1 second and about three orders of magnitude shorter than the numerical model of Richards' equation. The field data was further utilized to calibrate the soil hydraulic properties by matching the semi-analytical model's outcomes to the measured water levels in the well. A sensitivity analysis of the drywell response to variable hydraulic properties, climatic scenarios, and well configurations (depth and diameter) was conducted, demonstrating some practical applications for analysis, which may be used for adequately determining site-specific drywell design.

How to cite: Moreno, Z., Paster, A., and Kamai, T.: A Wetting-Front Model for Vadose Zone Infiltration via Drywells, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1708, https://doi.org/10.5194/egusphere-egu24-1708, 2024.

09:55–10:05
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EGU24-7923
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ECS
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On-site presentation
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Simone Gelsinari, Sarah Bourke, James McCallum, and Sally Thompson

Understanding the impact of climate change on groundwater recharge is crucial for the sustainable management of groundwater systems, especially when regulatory agencies are managing aquifers already fully allocated. Recharge emerges as the outcome of Critical Zone (CZ) processes such as interception, runoff, or plant water uptake that use or store water from rainfall as it traverses the soil-plant-atmosphere continuum. Consequently, recharge is best understood and observed through multiple observations that can characterise storage, potentials and transport of water both in the soil and in the groundwater. Understanding how these CZ processes respond to a variable climate is essential for informing groundwater allocation management and decision-making.

We present the results of field observations and a meta-analysis of recharge studies spanning the last 50 years in the Mediterranean climate area around Perth (Australia). This period coincides with a 15% reduction in winter rainfall, with the impacts on recharge partly revealed by the meta-analysis, but confounded by varying observation methods and sites. Seven field observation sites with consistent, multi-sensor instrumentation were therefore established to reveal recharge dynamics and estimate recharge fluxes. Electromagnetic soil moisture sensors provide vertical information across the soil profile (up to 10 meters below ground), complemented with soil water potential sensing at the surface and capillary fringe. ERT observations and manual soil moisture measurements in ancillary access tubes extend this information laterally (i.e. from 1D to 2D).  Groundwater depth, meteorological and remotely sensed information enables contextualisation of the observations. 

Historical data analysis shows that rainfall reductions lead to nonlinear (3 to 4 times higher), decreases in recharge. The installed monitoring stations reveal how the dynamics of wetting fronts are influenced not only by the climatic variables but also by the types of vegetation and their response to a drying climate. This suggests the presence of distinct local recharge mechanisms operating within the transient systems of the area. The insights obtained from these monitoring sites can be benchmarked against broader observations, such as data provided by remote sensing or borewell measurements, to generate databases of recharge estimates useful for models.

How to cite: Gelsinari, S., Bourke, S., McCallum, J., and Thompson, S.: Advancing estimates of groundwater recharge by integrating multi-sensor observations across the vadose zone in a drying climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7923, https://doi.org/10.5194/egusphere-egu24-7923, 2024.

10:05–10:15
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EGU24-15146
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ECS
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On-site presentation
Chengcheng Gong, Peter Cook, René Therrien, and Philip Brunner

Variably saturated subsurface flow models have been widely used in the context of water resources management as they conceptualize and simulate water flow in the unsaturated and saturated zone. By solving the Richards equation and using infiltration flux as an input, these models do not require groundwater recharge. As the models simulate the infiltration dynamics through the unsaturated zone, recharge is expected to be reliably extracted from such kinds of models. In this study, we explore to what extent variably saturated subsurface flow models can actually be used to extract groundwater recharge. In this context, we implement numerous definitions of groundwater recharge in a simple, variably saturated 1D model, extract groundwater recharge for a wide range of infiltration and groundwater dynamics imposed through boundary conditions, and assess the reliability of the extracted values. The results show that the value of recharge cannot be uniquely obtained from such kinds of models. The problem is attributed to the storage dynamics in the capillary fringe above the water table. However, it is important to keep in mind that if a variably saturated subsurface flow model of a project area is available, extracting recharge is superfluous as the model is capable of representing all the relevant flux and dynamics.  

Keywords: Variably saturated subsurface flow models; Groundwater recharge; unsaturated zone; Water resources management.

Reference: Gong, Chengcheng, Peter G. Cook, René Therrien, Wenke Wang, and Philip Brunner. "On groundwater recharge in variably saturated subsurface flow models." Water Resources Research 59, no. 9 (2023): e2023WR034920.

How to cite: Gong, C., Cook, P., Therrien, R., and Brunner, P.: Extraction of recharge in variably saturated subsurface flow models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15146, https://doi.org/10.5194/egusphere-egu24-15146, 2024.

Posters on site: Mon, 15 Apr, 16:15–18:00 | Hall A

Display time: Mon, 15 Apr 14:00–Mon, 15 Apr 18:00
A.89
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EGU24-833
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ECS
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Saurabh Kumar, Ajit Kumar Srivastava, and Richa Ojha

An improved understanding of temporal variability of soil hydraulic properties (SHPs) can lead to better prediction of soil water dynamics in agricultural fields. This study aims to quantify the temporal variations and trends in SHPs of an experimental agricultural plot in IIT Kanpur during rice and wheat crop seasons. Statistical analysis is performed to investigate the effects of crop-cover, sampling time and depth on temporal variability of SHPs. The soil samples were collected in 6 plots at depths of 10 cm, 25 cm, and 50 cm for the period 2022-23. The samples were analysed for variations in organic carbon content, bulk density (ρb), saturated hydraulic conductivity (Ksat) , saturated moisture content (θs), and soil water characteristic curve. The results show significant temporal variations in ρb and θs. The lowest temporal variation in observed in organic carbon content. The temporal trends in SHPs for both rice and wheat crops offer valuable insights into the dynamic nature of soil behaviour during crop cultivation. The findings of this study will contribute to better understanding of soil-water relationships, aiding farmers in optimizing irrigation practices and promoting sustainable agricultural management for improved crop productivity.

How to cite: Kumar, S., Srivastava, A. K., and Ojha, R.: Quantification of Temporal Variability of Soil Hydraulic Properties in an Agricultural Plot , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-833, https://doi.org/10.5194/egusphere-egu24-833, 2024.

A.90
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EGU24-2639
Dilia Kool and Nurit Agam

Water vapor adsorption is the least studied form of non-rainfall water inputs but is likely the most common one in arid and hyper-arid areas. It is determined by the magnitude of the downward gradient in water vapor pressure between the atmosphere and the soil; the surface area of the adsorbing soil; and the penetration depth of water vapor adsorption. Water vapor adsorption was measured using micro-lysimeters and profiles of relative humidity (RH) sensors in both loess and sand in the Negev desert, Israel, over the summers of 2021 and 2022. The RH sensor array allowed measurement of detailed changes in water content in the soil profile and provided an unprecedented insight into processes governing water vapor adsorption dynamics under arid conditions in-situ. The RH sensors significantly underestimated total water vapor adsorption, indicating that a finer array is needed to capture the full process. However, even with the current array, extremely small changes in water content were captured. With these measurements we explored the three main factors contributing to water vapor adsorption. The onset of a downward vapor pressure gradient coincided with the arrival of the sea breeze, indicating that the sea breeze is the primary source for water vapor adsorption in the uppermost soil layer. Water vapor adsorption was higher in loess than in sand, due to its finer texture and larger surface area. The most important finding of this research is that the dominant mechanism for water vapor flow under natural arid conditions (relative humidity in the soil (RHs) <100%) is different than under the generally assumed RHs = 100% conditions. Under natural arid conditions, temperature affects water vapor flow through advection rather than through diffusion. This means water vapor moves from lower to higher, rather than from higher to lower, temperatures. The fact that advection is a much faster process compared to diffusion potentially explains the rather deep penetration of water vapor adsorption observed in deserts.

How to cite: Kool, D. and Agam, N.: Water vapor adsorption and flow dynamics in dry desert soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2639, https://doi.org/10.5194/egusphere-egu24-2639, 2024.

A.91
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EGU24-4578
|
ECS
Shufeng Qiao

Understanding the change of soil hydraulic conductivity with temperature is a key to predicting the groundwater flow and solute transport in permafrost and seasonally frozen area. The most commonly used models for hydraulic conductivity during freeze-thaw cycles only consider the flow of capillary water in the soil and neglect water flowing along thin films around the particle surface. This paper proposed a new hydraulic conductivity model of frozen soil via Clausius-Clapeyron equation based on an unsaturated soil hydraulic conductivity model over the entire moisture range using analogy between freeze-thaw and dry-wet process in soils. The new model used a simple single equation to describe the conductivity behaviors resulting from both capillary and adsorption forces, thus accounting for effect of both capillary water and thin liquid film around soil. By comparing with other existing models, the results demonstrated that the new model is applicable to various types of soils and the predicted hydraulic conductivity is in the highest agreement with the observed data. Finally, our new model was validated with a thermal-hydrological benchmark problem and a laboratory experiment result, and the benchmark results indicated that the advective heat transfer was more significant and the phase change completed earlier when considering both capillary and adsorption forces than that only considering capillary forces. Further, the coupled flow-heat model with the FXW-frozen-M2 replicate well the results from a laboratory column experiment.

How to cite: Qiao, S.: A New Model for Predicting Hydraulic Conductivity of Soil during Freeze-thaw Processes that Accounts for Both Capillary and Adsorption Forces, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4578, https://doi.org/10.5194/egusphere-egu24-4578, 2024.

A.92
|
EGU24-5914
|
ECS
Leonardo Inforsato, Pablo Rosso, Ahsan Raza, Magdalena Main-Knorn, and Claas Nendel

Soil organic carbon (SOC) is a key driver of soil hydraulic properties like, field capacity and wilting point, necessary for in-field scale yield prediction using tipping bucket models. However, the labor-intensive nature of obtaining spatially distributed SOC often leads to its extrapolation using satellite imagery, resulting in significant inaccuracies in SOC prediction. In this study, we propose a Monte Carlo-based (MC) procedure to quantify the propagation of SOC error to simulated yield estimates. This procedure stochastically generates data, considering both uncorrelated and correlated data. For uncorrelated data, each SOC value is generated following an independent normal distribution. For correlated data, covariances are considered, accounting for the spatial correlation of in-field SOC variability. The autocorrelation between each pair of pixels is calculated, building a correlation matrix, which is submitted to the Cholesky decomposition, resulting in a lower triangular matrix. This matrix is then used to generate correlated SOC values for each pixel, maintaining the shape of the SOC clusters while varying the SOC value in each pixel according to its error. We validated our methodology using synthetic data, then used the methodology to assist error propagation of SOC with true data in a field located in Booßen, Germany. We generated 5000 SOC images, each with approximately 6000 pixels, and simulated the yield for each pixel. The results were analyzed by the field as a whole and each pixel across different images, by generating probability distributions for both. Another comparison was made by direct measurement between measured and simulated yields. Our results confirm the consistency of our method. In the specific scenario analyzed, preliminary results show that the SOC uncertainty was sufficient to explain the entire difference between the true and estimated crop yield, highlighting the importance of accurately assessing SOC uncertainty in yield prediction models.

How to cite: Inforsato, L., Rosso, P., Raza, A., Main-Knorn, M., and Nendel, C.: A Stochastic Approach to Quantifying Uncertainty in Soil Organic Carbon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5914, https://doi.org/10.5194/egusphere-egu24-5914, 2024.

A.93
|
EGU24-6734
Josh Heitman, Yongwei Fu, and Robert Horton

The presentation will focus on the interrelationships of soil hydraulic, thermal and electrical transport properties. We will highlight how some more easily measured transport properties can be used as surrogates for others, which cannot be readily measured. We will specifically illustrate how the thermo-TDR sensing platform can be used to collect detailed in situ thermal and electrical property measurements at millimeter to profile scale. We will utilize the interrelationships between hydraulic, thermal and electrical properties together with thermo-TDR measurements in order to demonstrate how soil density and structure can be determined in situ. We will also highlight opportunities for extending such approaches to other sensing platforms at other scales.

How to cite: Heitman, J., Fu, Y., and Horton, R.: Soil structure determined from interrelationships in hydraulic, thermal and electrical properties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6734, https://doi.org/10.5194/egusphere-egu24-6734, 2024.

A.94
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EGU24-7481
|
ECS
Daniel Schwarze, Johanna Metzger, Mathias Spieckermann, Joscha Becker, Yva Herion, Marc-Oliver Göbel, Jörg Bachmann, and Annette Eschenbach

Global warming is promoting extreme weather conditions like more frequent heavy rainfall events and longer periods of drought in central Europe. This can lead to an increase in hydrophobicity and hysteretic behavior of soils, potentially reducing its water retention capabilities and changing the soil water balance. These soil characteristics are also highly dependent on the amount and properties of soil organic matter (SOM). Climate change effects are expected to be particularly pronounced in sandy soils, which have comparatively low water retention capacities.

In this study, we will quantify the effects of SOM on soil hydraulic properties and analyze their impact on the soil water balance in hydrological models in comparison to data acquired by pedotransfer functions.

To cover a wide range of SOM content and properties, we sampled sandy soils (> 80% sand) from five different land use categories (arable land, heathland, grassland, deciduous and coniferous forest). The samples were taken in the Southwest of the Metropolitan region of Hamburg, near Lüchow-Dannenberg. The samples were analyzed for their total soil organic carbon and nitrogen content, and will further be analyzed for their fractions of particulate organic matter (POM) and mineral associated organic matter (MAOM). Hydrophobicity was determined using the water-drop-penetration-time test and contact angle measurements with the sessile drop method. Furthermore, the Integrative Repellency Dynamic Index (IRDI) will be determined for all topsoils to quantify the average hydrophobicity of the sample. Soil water retention is acquired using the porous plate method as well as the evaporation method (HYPROP), including wetting and drying curves. This data will serve as a starting point for simulations under different climate scenarios using HYDRUS.

The aim of this study is to improve our understanding on how hydrophobicity and water retention (wetting and drying) in sandy soils are influenced by the content and properties of SOM, and how this affects the results of hydrological models under different climate scenarios. This will contribute to improve the ability to assess future soil water dynamics, which is vital for sustainable land use and climate change adaptation.

 

The study is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany‘s Excellence Strategy – EXC 2037 'CLICCS - Climate, Climatic Change, and Society' – Project Number: 390683824, contribution to the Center for Earth System Research and Sustainability (CEN) of Universität Hamburg".

How to cite: Schwarze, D., Metzger, J., Spieckermann, M., Becker, J., Herion, Y., Göbel, M.-O., Bachmann, J., and Eschenbach, A.: Concept to quantify the effects of SOM on water retention hysteresis and hydrophobicity in sandy soils and their implication for soil water modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7481, https://doi.org/10.5194/egusphere-egu24-7481, 2024.

A.95
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EGU24-8608
|
ECS
Moritz Shore and Csilla Farkas

“rswap” is an R package under development for SWAP 4.2 with the goal of simplifying, automating, and improving user interaction with the model. The package functions by detecting and translating SWAP input files into R-compatible dataframes, allowing for easy and automated modifications to parameters. Modified model inputs can then be re-written to files and run in SWAP from the R console using "rswap". SWAP model output can be automatically imported into the R environment and visualized using a variety of (interactive) graphing functions. If observational data is provided by the user, then the package can adjust output settings to match (variables and depth).  Modelled and observed data can then be graphically compared in-line and “goodness-of-fit” statistics can be generated and plotted. Additionally, model runs can be saved and interactively compared with each other, functions are thoroughly documented with runnable examples, and a baseline runnable model setup can be automatically initialized. Further planned developments to the package include support for parallel running of model runs, enabling rapid automated sensitivity analysis, scenario analysis, as well as automated “hard calibration” routines and parameter estimation. Through this functionality, “rswap” can connect the SWAP model to an integrated development environment (IDE), such as “RStudio”, allowing users to efficiently perform all their work (setup, calibration, execution, analysis) in a single environment. Importantly, the packages allows for direct use of  SWAP with the vast array of research software on the R platform. “rswap” is an open-source project originally developed for use in OPTAIN (optain.eu) and has been applied in multiple case studies and thesis projects.

How to cite: Shore, M. and Farkas, C.: “rswap” – an R package for automated and command-based interaction with the SWAP4.2 model., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8608, https://doi.org/10.5194/egusphere-egu24-8608, 2024.

A.96
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EGU24-9410
|
ECS
Sebastián Bravo-Peña, Loes van Schaik, and Jos van Dam

The variability of soil hydraulic properties across different spatial and temporal scales leads to heterogeneous sub-surface water flows, affecting the accuracy of predicting soil water distribution and solute transport. Since soils such as Andosols can describe extreme physical behaviours and water rarely is in hydraulic equilibrium in the porous media, it is still challenging to derive hydraulic functions that realistically represent the influence of soil structure dynamics under different land uses, as well as to predict the occurrence of non-uniform flows at field conditions. This work aimed to describe the spatiotemporal variability of unimodal and dual-porosity (bi-modal) soil water retention (SWR) functions using high-resolution field observations in structured soil affected by compaction. We focused on the influence of water-filled pores volumes at wet and dry conditions, wetting/drying cycles, and soil structure dynamics using three depths (10, 20, and 60 cm). The land use was a diverse grassland sown in September 2019, including three compaction levels (0.65, 0.75, and 0.85 g cm-3, named Control, T1, and T2, respectively) in an Andosol of Southern Chile. A two-year 10-min-resolution dataset (June 2020 to June 2022) of soil moisture content (48 sensors) and matric potential (18 sensors) collected by 6 monitoring stations was analysed by i) separating wet and dry periods dynamics based on soil moisture states, ii) determining wetting and drying cycles using time derivatives of soil moisture content, and iii) fitting and comparing the parameters of unimodal and dual-porosity formulations of the Mualen-van Genuchten numerical solution. Separating soil moisture observations in wet and dry conditions, as well as in wetting and drying cycles, resulted in different SWR curves starting from contrasting water-filled pores volumes. This dynamic-based hydrological parameterisation resulted in a range of high goodness of fit (mean R2 of 0.89 ± 0.07 and 0.94 ± 0.06 for unimodal and dual-porosity van Genuchten models) while deriving SWR functions. However, the dual-porosity formulation better represented complex curvatures in SWR curves towards the soil surface in wet conditions, which would increase our capacity to describe near-saturation macropore dynamics at high resolution. Thus field observations allowed the representation of expected spatial variability between soil depths due to different physical properties and compaction influence. While at the same time, high-resolution time series were used to describe significant different SWR curves for wet and dry conditions when soil structure is affected by compaction, mainly influencing α and n parameters in unimodal formulations, and n1, α2, and n2 in dual-porosity formulations.

How to cite: Bravo-Peña, S., van Schaik, L., and van Dam, J.: Soil water retention function variability based on soil structure and moisture dynamics at field conditions affected by compaction in an Andosol, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9410, https://doi.org/10.5194/egusphere-egu24-9410, 2024.

A.97
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EGU24-10348
|
ECS
Dymphie Burger, Wulf Amelung, Heike Schimmel, Lutz Weihermüller, Harry Vereecken, and Sara Bauke

The infiltration of water into the soil, especially during extreme rainfall events, is controlled by soil hydraulic properties such as saturated hydraulic conductivity. Usually, the saturated hydraulic conductivity of the soil at larger scales is estimated by pedotransfer functions that use easily available soil properties such as soil texture, bulk density, and soil carbon content. Unfortunately, it has been already shown that those predictors do not contain the information for precise prediction of the saturated hydraulic conductivity. Moreover, it is widely accepted that the soil structure caused by aggregation, which defines the soil pore network, are important characteristics towards correctly estimating the saturated hydraulic conductivity.

To analyze and quantify the impact of aggregation on the saturated hydraulic conductivity we combined analyses of soil structure based on drop-shatter tests and aggregate size fractionation, with analyses of infiltration pathways via dye tracer application and in-field infiltration measurements. As soil structure is strongly influenced by soil management and climate, we sampled croplands, grasslands, and forests along a European climate gradient.

Our results indicate that both soil structure parameters and the classical predictors used in pedotransfer functions (soil texture, bulk density, and soil carbon content) had a significant influence on the saturated hydraulic conductivity. Regression models using soil structure parameters had a very similar Aikaike Information Criterion (AIC) as regression models without taking soil aggregation into account. This was different for the near-saturated hydraulic conductivity (K-2 cm), where the regression models based on soil texture, bulk density and soil organic carbon content  performed better than the model using soil structure parameters. Additionally, it was found that landuse and plant type had a large influence on soil structural parameters. We found less stained areas (0- 30 cm depth) in forests than in croplands and grasslands, which indicates more occurrences of preferential flow, and this was also  negatively correlated with the initial soil moisture at the time of measurement. In addition, higher levels of aggregation, indicated by a higher mean weight diameter of the soil aggregates, was associated with higher preferential flow as indicated by the dye tracer Both, stained area and peds and clods were influenced by the plant type as well, since the sites with vegetation having predominantly fibrous root systems responded differently than the sites with tap-rooted plants, trees, or heathland vegetation. The enhanced information on soil structure can therefore help us better understand landuse and land cover effects on saturated hydraulic conductivity and soil water infiltration.

How to cite: Burger, D., Amelung, W., Schimmel, H., Weihermüller, L., Vereecken, H., and Bauke, S.: Connecting soil structure and hydraulic properties under different land use on a European climate gradient, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10348, https://doi.org/10.5194/egusphere-egu24-10348, 2024.

A.98
|
EGU24-10493
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ECS
Anastasia Vogelbacher, Milad Aminzadeh, Mehdi H. Afshar, and Nima Shokri

Groundwater plays a crucial role in land-atmosphere interactions through its effect on soil moisture, evaporation and thus surface heat fluxes (1). Variation of rainfall patterns in a changing climate and the increase in water demands are expected to influence groundwater dynamics that affect soil moisture-air temperature feedback processes and subsequently the occurrence of heatwaves. The decline in groundwater levels with intensified abstraction could hinder its buffer capacities to impede soil desiccation and onset of heatwaves. The current understanding of the relationship between shallow groundwater tables and heatwave events is often limited to regional studies or specific land covers, with a very few endeavors seeking to characterize global-scale trends and responses. We thus aim to globally investigate the relation between groundwater levels and heatwave events considering different land cover types and environmental variables by conducting a wide-ranging statistical analysis. Our approach involved leveraging a comprehensive dataset, allowing us to distinguish potential links between groundwater tables and the frequency of heatwaves over a range of geographical and climatological parameters. The findings from our investigation provide valuable insights into the relationship between groundwater dynamics and heatwave frequency within the broader context of the interactions between soil moisture and air temperature. This information will aid in devising effective action plan to mitigate the adverse effects of climate change.

 

 

Reference:

(1) Maxwell, R., Kollet, S. Interdependence of groundwater dynamics and land-energy feedbacks under climate change. Nature Geosci1, 665–669 (2008). https://doi.org/10.1038/ngeo315

 

How to cite: Vogelbacher, A., Aminzadeh, M., Afshar, M. H., and Shokri, N.: Groundwater influence on the frequency of heatwaves: A global perspective, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10493, https://doi.org/10.5194/egusphere-egu24-10493, 2024.

A.99
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EGU24-10970
Johanna Clara Metzger, Volker Kleinschmidt, Truxton Oldridge, Matthias Beyer, and Annette Eschenbach

Macropore flow in structured soils constitutes an important component of soil water fluxes. This is especially true for unmanaged ecosystems. Preferential flow substantially affects ecohydrological separation, the partitioning of precipitation water into green (soil matrix, vegetation) and blue (recharge) water. Event characteristics, which are affected by changing climate, impact preferential flow; this, in turn, has an impact on ecohydrological separation and water resource availability. Though its importance is widely acknowledged since decades, it remains a challenge to measure preferential flow in soils. Additionally, small-scale heterogeneity of soil and environmental properties triggers spatial heterogeneity of preferential flow. In this study, we test the potential of zero-tension microlysimeters to measure preferential flow in a high spatial resolution. Zero-tension lysimeters have been used to sample soil water solution for chemical analysis. Methodical studies have shown that soil matric fluxes flow around zero-tension lysimeters and only gravity-driven water fluxes are captured. Using this to our advantage, we aim to develop a low-cost and simple method to sample preferential (gravity-driven) soil water fluxes in point measurements. This enables the implementation of a statistical design due to a high possible number of repetitions and the comparison with standard soil water status sensors due to similar scales. We are testing our lysimeters in a temperate mixed deciduous forest at Apelern, Lower Saxony, Central Germany. The soils are shallow and consist of weathered limestone intermingled with loess. By implementing transects starting from tree stems, we aim to cover a range of input fluxes and soil properties. We are combining lysimeters with measurements of soil water content, stand precipitation and soil properties. With our setup, we will be able to gain insight into the heterogeneity of preferential fluxes in situ and compare soil, stand and event impact factors to get a better understanding of the role of macropore flow in ecohydrological separation.

How to cite: Metzger, J. C., Kleinschmidt, V., Oldridge, T., Beyer, M., and Eschenbach, A.: Assessing heterogeneity of preferential soil water fluxes in situ with zero-tension microlysimeters in a temperate forest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10970, https://doi.org/10.5194/egusphere-egu24-10970, 2024.

A.100
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EGU24-11862
Sascha Iden, Efstathios Diamantopoulos, Magdalena Sut-Lohmann, and Wolfgang Durner

The Richards equation is de facto the standard model for simulating variably-saturated water flow in soils. It is based on the assumption that water content and matric potential are in instantaneous equilibrium. Their relationship is the water retention curve which is widely used to evaluate soil quality, to determine the effective pore-size distribution, and to derive the soil hydraulic conductivity curve. Experimental data collected over the last 6 decades show that the water retention curve depends not only on the history of wetting / drying, but also on the dynamics of water flow (transient vs equilibrium conditions). Many studies present experimental evidence on the hypothesis that the faster the water flow in soils, the more pronounced is the deviation of the dynamic retention curve from the equilibrium one. In this contribution, we present experimental data which show that these effects also occur during experiments in which water flow can be characterized as relatively slow. We conducted evaporation experiments on two soils, a sand and a silt loam, and varied the evaporation rate. Evaporation rates were controlled by wind speed, and flow interruptions were induced by temporarily covering the samples. We measured soil temperature and matric potential at different depths. The results show a relaxation of the matric potential with changes in wind speed, in particular during the flow interruptions. A complete analysis of the data requires a distinction between the vertical redistribution of moisture caused by changes in the evaporation rate, the effect of temperature on matric potential, and the “true” nonequilibrium between matric potential and water content. Contrary to the general assumption that bare-soil evaporation is a slow process during which equilibrium between water content and matric potential is ensured, our results show that dynamic nonequilibrium occurs even in the case of relatively slow, upward water flow. This results in a shift in the dynamic water retention curve estimated from evaporation experiments, indicating that more water is retained in the soil when water is flowing, as compared to static experiments.

How to cite: Iden, S., Diamantopoulos, E., Sut-Lohmann, M., and Durner, W.: Experimental evidence of non-equilibrium water flow during bare-soil evaporation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11862, https://doi.org/10.5194/egusphere-egu24-11862, 2024.

A.101
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EGU24-11976
Laurent Lassabatere, Deniz Yilmaz, Faye Waly, Didier Orange, Hanane Aroui, Djim ML Diongue, Saint-Martin Saint-Louis, Thierry Winiarski, Brice Mourier, Rafael Angulo-Jaramillo, Simone Di Prima, Olivier Roupsard, and Frederic C. Do

The comprehension of hydrological processes inherent in the water cycle and its constituents is of paramount significance when formulating adaptation strategies to address climate and global changes. The Sahel region serves a crucial role as a buffer zone between the arid desert and the more verdant and precipitation-laden areas of Senegal. The savanna region comprises a dynamic amalgamation of woody perennials intermixed with agricultural crops and pastures. The sustained vitality of this ecosystem hinges upon sustainable agriculture, mandating the judicious utilization of water resources. The formulation of strategies geared towards optimizing water resource management necessitates a comprehensive understanding of hydrological processes. This includes the investigation of water infiltration at the soil surface, the dynamics of water redistribution within the soil profile, and the mechanisms governing groundwater recharge. These scientific insights will help to develop effective strategies for the sustainable utilization of water resources within the Sahel region.  The intended investigation seeks to characterize the hydraulic properties of sandy soils that extensively prevail within the savanna ecosystem.

The utilization of water infiltration experiments coupled with corresponding modeling presents a robust framework for non-intrusive on-site hydraulic soil characterization. These methodologies have been widely employed across diverse contexts (Angulo-Jaramillo et al., 2019, for a review). To achieve this objective, the Beerkan method, initially proposed by Braud et al. (2005), involving the controlled infiltration of known water volumes into a designated ring, has been identified as a pertinent approach. Recently, Di Prima et al. (2016) have introduced an automated infiltrometer as a substitute for the manual Beerkan method, thereby streamlining and enhancing the procedural aspects of hydraulic soil characterization.

The study pursues a dual objective: (i) to characterize the hydraulic properties of sandy soil and delineate their spatial variability, both horizontally and vertically across the soil profile; and (ii) to assess the influence of the chosen water infiltration setup (Manual versus Automated Beerkan) on the obtained results. The investigation involved the excavation of three pits arranged as steps, providing access to five distinct horizons that spanned from the soil surface to a perched aquifer positioned at 2.5/3 m depth. Both Manual and Automated Beerkan experiments were conducted at the soil surface and for each horizon. Cumulative infiltrations were subjected to analysis using the BEST methods for precise determination of hydraulic parameters. Furthermore, bulk density and particle size distributions were determined for each Beerkan run by coring the soil at the conclusion of the experiment.

The examination of infiltration rates and hydraulic parameter profiles across the soil profiles, along with the comparative analysis of values derived from manual versus automated Beerkan runs, furnished pertinent insights to address the study's dual objectives.

References

Angulo-Jaramillo, R., et al., 2019. Journal of Hydrology. 576, 239–261. https://doi.org/10.1016/j.jhydrol.2019.06.007

Braud, I., et al., 2005. European Journal of Soil Science 56, 361–374. https://doi.org/10.1111/j.1365-2389.2004.00660.x

Di Prima, S., et al.,2016. Geoderma 262, 20–34. https://doi.org/10.1016/j.geoderma.2015.08.006

How to cite: Lassabatere, L., Yilmaz, D., Waly, F., Orange, D., Aroui, H., Diongue, D. M., Saint-Louis, S.-M., Winiarski, T., Mourier, B., Angulo-Jaramillo, R., Di Prima, S., Roupsard, O., and Do, F. C.: Manual versus Automated Beerkan run for characterizing the hydraulic properties of sandy soil in Senegal's Sahel, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11976, https://doi.org/10.5194/egusphere-egu24-11976, 2024.

A.102
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EGU24-12002
Lakshman Galagedara, Sashini Pathirana, and Manokararajah Krishnapillai

Incorporating biochar (BC) as a soil amendment has become a prominent agricultural management practice since it has many advantages. Most soils amended with BC have shown improvements in soil physical and hydraulic properties, including bulk density, soil porosity, water retention, field capacity, and permanent wilting point. Ground-penetrating radar (GPR) is a non-destructive geophysical technique that is used to study soil properties and state variables. Yet, there is a lack of research studying the influence of amendments on soil hydrology using GPR.  Therefore, this study was aimed at evaluating the ability of GPR in assessing the effect of BC on soil hydrology. The experiment was conducted under laboratory conditions using plastic containers measuring 28.6 cm in length, 20 cm in width and 16.4 cm in height. These plastic containers were filled up to 14 cm height with three different treatments (T); T1 (100% Sand+0% BC), T2 (99.5% Sand+0.5% BC), and T3 (98% Sand+2% BC) on a mass basis. Soil moisture sensors were placed horizontally at 2, 7, and 12 cm depths while packing the containers. The GPR data were collected using 1000 MHz center frequency transducers by keeping transmitter and receiver on opposite sides of the container (zero-offset profiling survey) at 20 cm antenna offset. Data were collected before, during, and after the wetting process over a one-hour timeframe. A 204 mL of water was applied every 4 min (13 times) to increase the soil water content at each time by 2% from initial water content. The GPR data were processed, and radargrams were prepared to observe the wetting front movement. Soil water contents were estimated utilizing the travel time of the GPR direct wave through the treatment media. GPR travel time and moisture sensor data were compared in each treatment. The GPR estimated soil water contents correlated well with moisture sensor data (correlation coefficient (r)>0.93) in all three treatments. Results have shown that the travel time of GPR direct wave responded differently for three treatments. The rate of change in GPR estimated soil water content over time exhibits an increase with the percentage of BC (T1<T2<T3). This suggests that the amendments with BC influence the soil water dynamics as expected, and the GPR effectively captures these rapid water content changes indicating its ability to monitor soil water dynamics non-destructively. Furthermore, the identification of the wetting pattern by GPR was noticeably distinct as compared to that observed with soil moisture probes in the BC amended treatments (T2 and T3), as compared to 100% sand (T1). Accordingly, our study demonstrates the capability of GPR in non-destructively capturing and distinguishing soil water dynamics influenced by BC amendments, emphasizing its potential for evaluating the impact of BC on soil hydrology.

How to cite: Galagedara, L., Pathirana, S., and Krishnapillai, M.: Ground-penetrating radar can ascertain the influence of biochar on soil wetting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12002, https://doi.org/10.5194/egusphere-egu24-12002, 2024.

A.103
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EGU24-12183
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ECS
|
Jannis Bosse, Sascha C. Iden, Wolfgang Durner, Magdalena Sut-Lohmann, and Andre Peters

A precise knowledge of soil hydraulic properties is crucial for many applications, with the unsaturated hydraulic conductivity being most challenging to measure accurately. Direct measurement under dry conditions presents difficulties, lacking simple and precise methods. While the simplified evaporation method (SEM) has become the standard for determining the water retention curve (WRC) and hydraulic conductivity curve (HCC), its classic implementation only provides conductivity values within a relatively narrow suction range measurable by tensiometers, typically between 60 and 1000 cm.

In this study, we extended the experimental setup of the SEM by incorporating small sensors to measure temperature and relative humidity alongside the tensiometers. Applying the Kelvin equation, this addition allows for suction measurements between the wilting point and air-dry conditions. Using this setup, we conducted evaporation experiments on soils spanning various textures, from silt loam to pure sand. Analyzing the data through (i) inverse modeling using the Richards equation and (ii) the SEM revealed that combining tensiometers and relative humidity sensors facilitates the determination of HCC over a broad moisture range. This includes the suction range covered between the measurement ranges of the sensors, given proper interpolation between the two sensor types.

Crucially, successful inverse modeling relies on a suitable parametric representation of the soil hydraulic properties, considering water adsorption, film, and vapor flow. Our findings indicate that the classic SEM evaluation tends to overestimate HCC in the tensiometer's measuring range and underestimate it in the hygroscopic range, especially in coarse-textured soils with a narrow pore size distribution. Despite this limitation, the proposed test setup, when coupled with the SEM, offers practical advantages due to its relative simplicity and ease of data evaluation.

How to cite: Bosse, J., Iden, S. C., Durner, W., Sut-Lohmann, M., and Peters, A.: Extending the measurement range for determining soil hydraulic properties with the simplified evaporation method using relative humidity sensors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12183, https://doi.org/10.5194/egusphere-egu24-12183, 2024.

A.104
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EGU24-13115
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ECS
Sara Sayyadi, Daniel Rasche, Marvin Reich, Theresa Blume, and Andreas Güntner

In this study, spatial and temporal variations of soil moisture and water storage were monitored with two complementary methods: terrestrial gravimetry and cosmic ray neutron sensing (CRNS). CRNS monitors near-surface soil moisture by measuring low-energy neutron abundance in the near-surface atmosphere, which inversely correlates with soil moisture in the top decimeters of the soil. Terrestrial gravimetry monitors water storage variations in an integrative way over the entire unsaturated zone and the groundwater. Both methods allow for non-invasive spatially integrated field-scale monitoring around the instruments.

The study area is the Selke catchment in Central Germany with an area of 456 km². It has notable variations in topography, land use, and meteorology from the lowlands to the low mountain ranges. A combined approach was applied for terrestrial gravimetry: continuous stationary and time-lapse network surveys. We deployed a gPhone in a container-based housing (SolarCube) which serves as a base station for the relative gravity campaigns. Using two CG-6 gravimeters, the campaigns were conducted at six sites within the catchment area with co-located CRNS installations. In total five relative gravity surveys were carried out from July to October 2023. Each of them consisted of a two-day campaign where each survey point was visited three times by the two gravimeters. In order to ensure a high quality of the gravity data, capable of resolving a signal in the magnitude typical for hydrological processes in the area, a network adjustment of the repeated survey data was carried out. This included device-specific drift estimations. The results are combined with the continuous time series of the gPhone and analyzed jointly in a spatio-temporal approach with CRNS and in-situ soil moisture observations. Temporal dynamics of storage dynamics are assessed and spatial differences between the upland and the lowland areas are analyzed.

How to cite: Sayyadi, S., Rasche, D., Reich, M., Blume, T., and Güntner, A.: Advancing hydrological monitoring: Terrestrial gravimetry surveys in the Selke Catchment, Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13115, https://doi.org/10.5194/egusphere-egu24-13115, 2024.

A.105
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EGU24-13430
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ECS
Ecological Accommodation of Soil Hydraulic Properties Driven by Industrial Reforestation in Central Chile 
(withdrawn)
Matthew Tippett-Vannini and John Selker
A.106
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EGU24-14811
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ECS
Ping Xin, Charles Pesch, Trine Norgaard, Lis Wollesen Wollesen de Jonge, Maarit Mäenpää, Goswin Heckrath, and Bo Vangsø Iversen

Macropore transport is an important process of phosphorus (P) loss from tile-drained agricultural land to surface waters where P inputs may cause accelerated eutrophication. Many laboratory experiments or plot studies have shown that P loss by macropore transport increases with increasing concentrations of mobilizable P in the topsoil. However, operational models that quantify the risk of P losses by macropore transport based on typically available information on soil properties, including P status and soil hydrological properties, are currently lacking.

This study has collated and analyzed comprehensive existing data from standardized column-leaching experiments with 193 topsoils from different locations in Denmark. In addition to general physical and chemical soil properties including soil P pools, water, and P transport were measured on the large undisturbed soil columns. This data has been used to investigate relationships between P loss and soil properties under varying degrees of macropore transport. Specifically, we have used two statistical methods to analyze relationships between variables and to explore predictive models – multiple linear mixed models (MLMM) and structural equation modeling (SEM). The latter technique allows for testing complex causal relationships among observed and latent variables.

Our SEM approach has so far yielded rather poor model fits, and the model structures for estimating the loss of dissolved and particulate P from the columns were characterized by low significance. This was partly due to missing data. In contrast, different MLMM fitted the measured dissolved and particulate P losses satisfactorily. Water-extractable P and saturated hydraulic conductivity were the most important variables for estimating dissolved P losses, while colloid mobilization in soils and tritium leaching breakthrough time explained particulate P losses to a large degree.

Our initial statistical analyses show that P loss in dissolved and particulate form from large columns under macropore runoff scenarios can be reasonably explained by soil properties that are typically mapped in Denmark. This approach could bridge empirical and mechanistic modeling and facilitate mapping the risk of P loss by macropore transport.

How to cite: Xin, P., Pesch, C., Norgaard, T., Wollesen de Jonge, L. W., Mäenpää, M., Heckrath, G., and Vangsø Iversen, B.: Predicting phosphorus loss from structured soils through macropores, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14811, https://doi.org/10.5194/egusphere-egu24-14811, 2024.

A.107
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EGU24-16485
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ECS
Jere Remes and Jarkko Okkonen

The modeling of the coupled thermo-hydro-mechanical processes within a soil undergoing freeze-thaw cycles is an increasingly relevant problem in the era of accelerating climate change. One can hope to alleviate and prepare for infrastructure damages due to e.g., frost heave and frost quakes by modeling the interplay of hydrology and soil mechanics and identifying at-risk structures and environmental profiles (i.e. temperature gradient, snow cover, soil water/ice saturation) that make those structures susceptible to said damages.

Our work is focused on developing a linked computational framework for thermo-hydro-mechanical modeling of soils. We achieve this currently by linking the state-of-the-art thermo-hydrological modeling of Amanzi-ATS with the thermo-mechanical modeling capabilities of OpenGeoSys, allowing us to have an accurate understanding of both the intricate hydrology of freezing soils as well as being able to determine the stress and pressure fields within the system. This framework is then to be applied to understand the mechanics and triggering circumstances at the frost quake site at Talvikangas in Oulu, Finland as well as developing a risk-assessment tool for damages to infrastructure and built environment.

How to cite: Remes, J. and Okkonen, J.: Modeling mechanical stress in freezing soils: sub-Arctic infrastructure, built environment and frost quakes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16485, https://doi.org/10.5194/egusphere-egu24-16485, 2024.

A.108
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EGU24-17257
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ECS
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Lena M. Scheiffele, Katya Dimitrova Petrova, Maik Heistermann, and Sascha E. Oswald

Brandenburg is among the driest regions in Germany, and heavily relies on groundwater resources for both agricultural and drinking water supply. Already suffering from declining groundwater tables, climate change is expected to exacerbate the situation. For a sustainable management of groundwater resources, the rate of groundwater recharge (GWR) is a key variable. Yet, its quantification remains a challenge, as it cannot be measured directly at the field scale

One way to estimate GWR is using vadose zone models to simulate the local water balance and the vertical percolation of water towards the groundwater. Observations of soil moisture (SM) in the root zone can provide a means to calibrate such models so that they can adequately represent the local water balance. However, conventional point-scale SM observations notoriously suffer from a lack of horizontal and vertical representativeness, compromising the validity of the calibration.

In this study, we explore the potential of cosmic-ray neutron sensors (CRNS) to address this issue. CRNS allow for non-invasive SM monitoring of the shallow root zone at the hectare-scale. We use daily CRNS-based soil moisture estimates to calibrate the vadose zone model HYDRUS-1D, and hence to derive daily estimates of the downward water fluxes below the root-zone, as an approximation of GWR.

For this purpose, we explore a unique dataset that was obtained in a research site near Potsdam, Brandenburg, over a period of more than three years. The site features a diversity of agricultural plots, and sits on a gentle hillslope over a glacial till aquifer, with the groundwater table at depths between 1 to 10 m. In an area of around 10 ha, we operated eight CRNS sensors and 27 SM profile probes, complemented by measurements of soil texture and soil hydraulic properties, among others.

In various simulation experiments, we evaluate the added value of using CRNS-based soil moisture estimates for model calibration, as a replacement or as a supplement of conventional profile probes. Based on a calibrated model, we also assess long-term (centennial) changes of GWR.

How to cite: Scheiffele, L. M., Dimitrova Petrova, K., Heistermann, M., and Oswald, S. E.: Groundwater recharge estimates in agriculturally managed site in Northeast Germany: combining Cosmic ray neutron sensing and soil hydrological modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17257, https://doi.org/10.5194/egusphere-egu24-17257, 2024.

A.109
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EGU24-19388
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ECS
Anne Doat, Caroline Vincke, and Mathieu Javaux

Heterogeneous soils with stone fractions are very common in non-agricultural areas. The characterization of their hydraulic properties is important but face technical challenges. Therefore, the retention of the stony fraction (larger than 2 mm) is often considered as null. However, when soil stone content is large (>15%), even a slight change of water with suction in the stone fraction will affect the shape of the bulk soil retention curve.

In this study, we analyzed the retention data, between pF 0 and pF 4.2, of more than 2400 aggregates extracted from 48 soil horizons in forests down to 2-m depth. For each horizon, at each suction level, we characterized water content and stone content of at least 8 replicates of aggregates. We propose a novel methodology to extract and separate the hydraulic properties of the stony and of the fine fractions from these data. It proved to be efficient beyond 15% of stone content.

In general, the change of volumetric water content between pF 2 and pF 4.2 was below 5% for stones but for some of them, it could reach up to 15%.  In addition, we could propose a general expression of the bulk retention curve that explicitly contains the fraction of stones. It is observed that the shape of the bulk retention curve (mono or bimodal) evolves with stone content for a given horizon.

How to cite: Doat, A., Vincke, C., and Javaux, M.: Modeling the impact of stone content on the shape of water retention curve, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19388, https://doi.org/10.5194/egusphere-egu24-19388, 2024.

A.110
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EGU24-19745
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ECS
Mateusz Zawadzki

The Soil-Water-Atmosphere-Plant (SWAP) model has been continuously developed since 1974 and has gained a community of users. The need for clearer and more reproducible model development and interpretation drove the development of wrapper packages in R, such as SWAPTools and RSWAP. Due to the steady increase in the community of Python users, it became important to provide similar interface tools written in Python. This work introduces the pySWAP Python package, developed as a wrapper for the SWAP model.

A key feature of pySWAP is its user-friendly, object-oriented design. Users provide the essential model setup, for example, in the form of a Jupyter notebook, and the package creates the input files while preemptively checking for errors. This ensures a smooth setup and execution process, significantly reducing common user errors and streamlining the model setup. This is especially beneficial for those new to SWAP, who can easily access documentation through their Integrated Development Environments (IDEs). The package also runs the model, captures the results, and provides tools for simple data visualization.

pySWAP also aims to optimize work with multiple scenarios and the parameter estimation process. This is achieved through the integration of a SQLite database, which stores data from intermediate simulations. This method not only reduces file storage requirements but also enhances the efficiency of data retrieval and manipulation during and after simulation runs. The use of open-source SQLite is also beneficial for sharing models between users, as it can efficiently store input and output data of multiple models in a single file, accessible on all operating systems. Furthermore, we are in the process of developing a Dockerized version of PySWAP, which may further improve collaboration on models and allow users to effortlessly deploy and execute simulations developed on local machines on supercomputers.

As a proof-of-concept, we use pySWAP in the Grow project to develop a SWAP model for a pilot site in Kinrooi, East Belgium, where treated wastewater is reused through a subirrigation system.

How to cite: Zawadzki, M.: pySWAP: Python wrapper for SWAP hydrological model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19745, https://doi.org/10.5194/egusphere-egu24-19745, 2024.

A.111
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EGU24-20755
Jose A Sanchez-Espigares, Basem Aljoumani, and Birgit Kleinschmit

This study proposes an integrated methodology to advance the estimation and uncertainty analysis of soil pore electrical conductivity. Drawing on previous work from Aljoumani et al. (2015), where modifications were made to the Hilhorst model, and subsequent enhancements in Aljoumani et al. (2018), this research unfolds in a systematic manner.

Commencing with a comprehensive examination of critical data from the Aljoumani el al.(2015) study, including bulk electrical conductivity, soil permittivity, and pore water permittivity, we transition into the construction of an improved Hilhorst model. This advanced model convert the deterministic Hilhorst model to stochastic model incorporates linear dynamic modeling and the Kalman filter, enabling precise estimation of soil salinity (pore electrical conductivity) and determination of corresponding offsets.

To address uncertainty comprehensively, we employ a multifaceted strategy. Beginning with the modeling of relationships using the Long Short-Term Memory (LSTM) algorithm, an artificial recurrent neural network, we intricately examine the interplay between the original time series of soil permittivity, pore water permittivity, and bulk electrical conductivity.

Subsequently, we utilize bootstrapping to generate 1000 series for soil permittivity and pore water permittivity. The LSTM model then produces 1000 series of bulk electrical conductivity, using the generated soil and pore water permittivity series as input.

Applying the modified Hilhorst model to the 1000 series obtained from bootstrapping and the LSTM model, we obtain 1000 models, each providing 1000 offsets and predicted pore water electrical conductivity series. Returning to the original data, the modified model is applied to construct predicted series of pore electrical conductivity. Upper and lower bounds are established using the calculated 5th and 95th percentiles of the 1000 offset values from the generated data.

In summary, this integrated methodology not only ensures accurate estimations of soil pore electrical conductivity but also provides a robust framework for quantifying uncertainty comprehensively.

How to cite: Sanchez-Espigares, J. A., Aljoumani, B., and Kleinschmit, B.: An Integrated Approach for Estimation and Uncertainty Analysis of Soil Pore Electrical Conductivity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20755, https://doi.org/10.5194/egusphere-egu24-20755, 2024.

Posters virtual: Mon, 15 Apr, 14:00–15:45 | vHall A

Display time: Mon, 15 Apr 08:30–Mon, 15 Apr 18:00
vA.22
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EGU24-6420
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ECS
|
Asma Hmaied and Claude Hammecker

Abstract

The hydrological cycle is strongly affected by climate changes causing extreme weather events with long drought periods and intense rainfall events. To predict the hydrological functioning of Tunisians catchments, modelling is an essential tool to estimate the consequences on water resources and to test the sustainability of the different land uses. Soil physical properties describing water flow, are therefore essential to feed the models and need to be determined all over the watershed.

In order to complete this task, lightweight, cost effective but robust methods are needed. In the present study, both physically based and empirical models or pedo-transfer functions (PTF) have been used to estimate unsaturated soil hydraulic properties based on particles size distribution (PSD), and straightforward in-situ infiltration experiments.

The specific Pedo-Transfer Functions (PTFs) embedded within the Rosetta model, the physically grounded Arya-Paris model, and the Beerkan Estimation of Soil Transfer parameters (BEST) have been specifically developed to gauge soil hydraulic parameters based on soil texture, bulk density, and, eventually, outcomes from single-ring infiltration experiments. These models were applied to a diverse array of soil types from both Northern and Central Tunisia, with a subsequent comparative analysis aimed at evaluating their potential applicability and individual performances.

Consequently, the estimated parameters derived from these models were incorporated into Hydrus to compute water flow in the vadose zone under the actual weather conditions prevailing in Tunisia. The resultant effects on the calculated water balance, encompassing infiltration, drainage, and runoff, were systematically compared for a comprehensive understanding of their implications.

Results show that soil hydraulic parameters determined with different techniques are significantly different. The results for simulated water balance over 3 years, show also differences especially for intense rainfall events. It seems that the BEST method is a valuable technique for estimating soil hydraulic parameters, offering a cost-effective and practical alternative to traditional methods, especially as it leverages on experimental infiltration data.

 

How to cite: Hmaied, A. and Hammecker, C.: Direct measurement and indirect estimation of unsaturated soil hydraulic properties in Tunisian soils., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6420, https://doi.org/10.5194/egusphere-egu24-6420, 2024.

vA.23
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EGU24-12145
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ECS
Saint Martin Saint Louis, Fasnet Boncourage, Simone Di Prima, Dieuseul Prédélus, Rafael Angulo-Jaramillo, and Laurent Lassabatere

Adapting cities to climate and global changes requires tremendous progress in managing the water cycle in cities. So far, the water pathways are disconnected from the natural water cycle in urban areas. Runoff water is collected and routed to sewer systems. Best management practices were then developed to restore the natural water cycle by promoting water infiltration into specific urban drainage systems. These are often called “SUDS” for Sustainable Urban Drainage Systems and infiltrate the runoff water collected over urban catchments. However, SUDS may lose their capability to infiltrate water as the soil clogs and becomes less permeable. For these devices, soil hydraulic conductivity must be monitored over time.

Water infiltration techniques have been developed to characterize the soil hydraulic properties. The Beerkan method was pioneered by Braud et al. in 2005 and then used by many soil scientists (Angulo-Jaramillo et al., 2016). Several algorithms were developed to treat the data and estimate the soil hydraulic properties. In 2006, Lassabatere et al. (2006) initiated the BEST method to identify the saturated hydraulic conductivity and the whole set of unsaturated hydraulic parameters from Beerkan runs combined with field data (bulk density and particle size distribution). Since then, the method has been improved and adapted to many types of soils and configurations (see Angulo-Jaramillo et al., 2019, for a review).

The Beerkan run is easy to perform. It requires one operator to prepare known volumes of water, infiltrate them into a ring inserted in the soil, and score the infiltration times. The cumulative infiltration, which assigns the cumulative infiltrated volume to the infiltration time, is the raw data that is used in most hydraulic characterization algorithms. However, its ease of use requires human resources (one operator) and may be time-consuming, particularly for fine soils that infiltrate very slowly. Di Prima et al. (2016) recently designed an automated infiltrometer that replaces the operator. The device automatically supplies the water before desaturation of the soil surface and records the infiltrated volume as a function of time. This device has been deployed for several studies, allowing the hydraulic characterization of several types of soils under several field conditions.

However, so far, no studies have focused on comparing the automated infiltration, referred to as “Automated Beerkan,” and the manual version of the Beerkan runs. In this study, we performed the two types of runs at the same places in order to avoid uncontrolled variations due to spatial variability in urban soils. We present the cumulative infiltrations obtained at the same point with the automated Beerkan and the original Beerkan (manual version). The cumulative infiltrations were inverted using the BEST methods, and the obtained hydraulic parameters were compared.

Di Prima, S., et al.,2016. Geoderma 262, 20–34. https://doi.org/10.1016/j.geoderma.2015.08.006

Angulo-Jaramillo, R., et al., 2016. Springer, Switzerland. https://doi.org/10.1007/978-3-319-31788-5

Angulo-Jaramillo, R., et al., 2019. Journal of Hydrology 576, 239–261. https://doi.org/10.1016/j.jhydrol.2019.06.007

Braud, I., et al. 2005. European Journal of Soil Science 56, 361–374. https://doi.org/10.1111/j.1365-2389.2004.00660.x

Lassabatere, L., et al., 2006. Soil Science Society of America Journal 70, 521–532. https://doi.org/10.2136/sssaj2005.0026

How to cite: Saint Louis, S. M., Boncourage, F., Di Prima, S., Prédélus, D., Angulo-Jaramillo, R., and Lassabatere, L.: Comparing manual versus automated Beerkan runs for the estimation of water infiltration and soil hydraulic parameters for an urban soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12145, https://doi.org/10.5194/egusphere-egu24-12145, 2024.