HS8.3.4 | Flow and transport in the vadose zone – Experimental and modeling approaches for characterizing processes in a heterogenous soil-plant system
EDI
Flow and transport in the vadose zone – Experimental and modeling approaches for characterizing processes in a heterogenous soil-plant system
Convener: Arno Rein | Co-conveners: Giuseppe Brunetti, Peter Dietrich, Cafer Turgut, Jiri Simunek
Orals
| Fri, 28 Apr, 08:30–10:15 (CEST)
 
Room 3.16/17
Posters on site
| Attendance Thu, 27 Apr, 08:30–10:15 (CEST)
 
Hall A
Posters virtual
| Attendance Thu, 27 Apr, 08:30–10:15 (CEST)
 
vHall HS
Orals |
Fri, 08:30
Thu, 08:30
Thu, 08:30
Understanding hydraulic processes in the unsaturated zone is crucial for assessing and mitigating climate change impacts, such as droughts that effect soil water storage and induce stress on vegetation including forests and agricultural land. Furthermore, knowledge of chemical fate and transport processes is essential for assessing soil functions and chemical risks, such as those arising from agricultural activities (fertilizers, pesticides, etc.). This requires a profound understanding of coupled dynamic processes in the soil-groundwater-plant system, including unsaturated water flow and reactive solute transport, as well as plant uptake of water, nutrients and pollutants.
Flow and transport processes in the vadose zone can encompass both the subsurface matrix and preferential flow paths, which can contribute differently to water flow and storage and chemical fate. The influence of vegetation is not only important at the upper boundary of the subsurface, but plants are also an active participant in the water and chemical cycle: thus, the consideration of coupled dynamics might be required.
This session aims to illustrate and discuss current research on flow processes within the unsaturated zone, including field studies and experiments, modeling approaches, and simulation studies. Studies may focus on soil processes or coupled soil-plant processes. More specifically, we encourage researchers to participate with contributions among the following topics:
• Monitoring of flow and transport in the unsaturated zone, from field and lysimeter studies to pore scale observations
• Measuring and modeling environmental tracers, including stable water isotopes, for characterizing subsurface flow processes at different spatial and temporal scales
• Geophysical investigations for determining structures and mechanisms that can induce preferential flow and transport in different dimensions
• Identification and quantification of water and solute transport processes, especially in the context of changing climate conditions that alter biogeochemical processes
• Investigating the influence of plant uptake and coupled soil-plant processes
• Development of new modeling approaches for describing unsaturated flow and reactive transport, as well as coupled soil-plant dynamics
• Sensitivity and uncertainty for model diagnostics and criticism, as well as surrogate-based numerical approaches to reduce the computational cost

Orals: Fri, 28 Apr | Room 3.16/17

Chairpersons: Arno Rein, Giuseppe Brunetti, Jiri Simunek
08:30–08:35
08:35–08:55
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EGU23-11064
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ECS
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solicited
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Highlight
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Virtual presentation
Naaran Brindt, Jiuzhou Yan, Xinying Min, Jean-Yves Parlange, and Tammo Steenhuis

Understanding how water infiltrates soils is essential in groundwater recharge and surface runoff predictions and agrochemical contamination assessment. Infiltration fronts are often envisioned as flat, uniform wetting fronts in which water content and pressure decrease monotonically. However, water infiltration occurs as unstable gravity-driven flow in homogeneous coarse-textured or water-repellent soils as fingers, bypassing most of the soil. A characteristic of these fingers is that the advancing tips are near saturation, and the moisture content and pressure decrease behind the front. Despite many approaches to modeling this flow, the explanation for the increased pressure at the wetting front of these unstable flow fingers has remained elusive. We postulated a discontinuous matric potential at the wetting front resisting uniform water entry in the dry soil. Instead, water moves one pore at a time across the front, inducing high localized velocities that increase the static contact angle to a dynamic one, which the Hoffman-Jiang equation can describe. It causes the matric potential to increase at the front. These high velocities during pore invasion are akin to what is known as Haines jumps which require high-frequency sensors to detect.

In this study, we aimed to prove the hypothesis experimentally and refine the theory using a high-speed camera and high-frequency pressure measurements of water infiltration into partially wettable sand. A 30X50X1.6 mm glass flowcell was packed with air-dry quartz sand. Water infiltration to the cell was 15 μl/min. Porewater pressure was recorded at 500 Hz through a needle tensiometer at the back of the flow cell wall. A high-resolution, high-speed camera recorded the pore invasion at 500 fps over an area of 32X32 mm surrounding the tensiometer. A second set of experiments was performed at even greater magnification, looking at a single pore (5X5 mm) where the wetting front’s contact angle could be measured visually during infiltration. The results showed that water advanced as a series of invasion events through one or two pores lasting a few milliseconds separated by longer periods where the front was static. The invasion pore flow velocities exceeded the saturated hydraulic conductivity by three orders of magnitude. In addition, the high magnification experiment found that the changes in the contact angle during pore invasion and the observed pore water velocities agreed with the Hofmann Jiang predictions. Our experimental results offer new insights into how water infiltrates the soil, as studies rarely measure infiltration with such small spatial and temporal scales.

How to cite: Brindt, N., Yan, J., Min, X., Parlange, J.-Y., and Steenhuis, T.: Improved understanding of unstable finger formation in partially wettable soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11064, https://doi.org/10.5194/egusphere-egu23-11064, 2023.

08:55–09:05
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EGU23-8316
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On-site presentation
Ursula Noell, Erkki Hemmens, Bernd Ahrends, Susanne Stadler, Stefan Fleck, and Klibw-gw working group

Effective management of groundwater resources requires conclusive evidence and understanding of forest management effects (tree species selection, harvest intensities, forest rotation periods) on groundwater recharge. The high spatial variability of forest soil characteristic hampers an area representative measurement of forest soil moisture distribution and flow processes in the unsaturated zone. This results in high uncertainties in the detection of tree species difference of water balance and groundwater recharge in forests. We attempt to delineate this heterogeneity by combining different investigation methods and forest stands of different tree species. From 2019 – 2022 we investigated a Norway spruce stand (Picea abies (L.) KARST.) in the Solling mountains (AMT 7.3°C, AMP 1168 mm). The observation shows higher moisture contents close to the trees, where the root density is highest. We calculated a site-specific function relating electrical resistivity to soil water content and used this to reconstruct moisture changes down to a depth of one meter below the rooting zone. Recharge seems to happen not only in winter but also in summer after intense precipitation events. During a severe spring drought in 2020, the water content dropped markedly in the rooting zone. In 2022 we started the observation of the water balance in a lowland Scots pine stand (Pinus sylvestris) with locally regenerating red oak (Quercus rubra) in the shrub layer. The geophysical monitoring using electrical resistivity tomography discovered again lower resistivity indicating higher moisture content close to the trees where root density is highest. The application of different inversion smoothness constraints revealed differences in resulting electrical resistivity values, showing the non-uniqueness of the inversion results. This presents a challenge, relating single point soil water measurements to ERT 3D inversion results and calls for the need to construct a site-specific Archie function by using simultaneous water content measurements at the site rather than laboratory measurements. The investigations will continue in stands of Douglas fir (Pseudotsuga mentiesii), red oak (Quercus rubra), common oak (Quercus robur) and European beech (Fagus sylvatica).

The project is funded by the Forest Climate Fond under the joint leadership of BMUV and BMEL (Federal Ministry for the Environment, Nature Conservation, Nuclear Safety and Consumer Protection and the Federal Ministry of Food and Agriculture (KLIBW-GW:FKZ: 2220WK39B4 and 2220WK39B4)).

How to cite: Noell, U., Hemmens, E., Ahrends, B., Stadler, S., Fleck, S., and working group, K.: Reconstructing spatial variability of forest soil water characteristic by using a combination of electrical resistivity tomography and local soil water content measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8316, https://doi.org/10.5194/egusphere-egu23-8316, 2023.

09:05–09:15
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EGU23-8548
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On-site presentation
Christine Stumpp, Marleen Schübl, and Giuseppe Brunetti

Groundwater recharge is a key component of the hydrologic cycle, yet its direct measurement is difficult. An alternative is its inverse estimation with a combination of physically based numerical models and soil water observations. However, simulated water fluxes are affected by model predictive uncertainty which are often not considered when simulating and predicting groundwater recharge rates. Therefore, the objective of this study was to use of long-term soil water content measurements at 14 locations from the Austrian soil water monitoring program to quantify and compare local, potential groundwater recharge rates, their temporal variability, and predict future changes in potential groundwater recharge for different climate scenarios. Observations were coupled with a Bayesian probabilistic framework to calibrate the model HYDRUS-1D and assess the effect of model predictive uncertainty on simulated recharge fluxes. Estimated annual potential recharge rates ranged from 44 mm/a to 1319 mm/a with a relative uncertainty (95% interquantile range/median) in the estimation between 1-39%. Recharge rates decreased longitudinally, with high rates and lower seasonality at western sites and low rates with high seasonality and extended periods without recharge at the southeastern and eastern sites of Austria.  Higher recharge rates and lower actual evapotranspiration were related to sandy soils. Future recharge predictions at the median remained close to past rates, except for sites in the East, where they increased. In general, predictions varied drastically between different climate models and emission scenarios, especially for the summer months. Across all projections, an increase in winter recharge at the western sites was predicted, due to higher temperatures with less snow accumulation and/or higher amounts of winter precipitation, followed by decreasing recharge rates in spring. Decreasing tendencies in groundwater recharge were stronger at western sites and at higher altitudes, with longer drought periods lasting until later within the calendar year. Uncertainty in recharge prediction was largely dominated by the difference in climate projections, only at the dry sites in the East and for shorter time periods, soil hydraulic parameter uncertainties played a role.

How to cite: Stumpp, C., Schübl, M., and Brunetti, G.: Groundwater recharge estimation and uncertainty analysis for various soils in Austria, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8548, https://doi.org/10.5194/egusphere-egu23-8548, 2023.

09:15–09:25
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EGU23-489
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ECS
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On-site presentation
Judith Mach, Laura Kinzinger, Stefan Seeger, Simon Haberstroh, Maren Dubbert, Christiane Werner, Markus Weiler, and Natalie Orlowski

Soil-plant interactions and root water uptake are important factors of the soil-plant-atmosphere continuum. Characterizing root water uptake dynamics in different forest stands can help to predict water stress due to climate change. Governing factors that define tree root water uptake are environmental conditions, soil hydraulic properties, species-specific rooting patterns as well as intra- and interspecific competition. As spatial-temporal patterns of root water uptake cannot be measured directly, simplified assumptions are often either based upon homogenous soil conditions or on a static root water uptake profile. This study combines high-resolution in-situ measurements of water stable isotopes of xylem and soil moisture with a set of 1D soil hydrological and transport models of the vadose zone (Hydrus 1D) to investigate dynamics in root water uptake patterns of two competing tree species in three different forest stands. 

We measured in-situ water isotopic signature in different soil depths as well as in spruce and beech xylem continuously for two vegetation periods (2021-2022) including two artificial tracer experiments, a wet period in 2021 and a drought period in 2022. Three stands were compared: i) pure beech, ii) pure spruce and iii) mixed beech and spruce, measuring sap flux, leaf water potential, soil moisture, matric potential, throughfall and stemflow. In order to address different factors of soil heterogeneity, the vadose zone is represented by a set of models covering the range of measured soil conditions. Each model is calibrated against soil water content as well as isotope measurements and subsequently related to sap flux measurements. This allows for separating effects of soil heterogeneity and to analyze the interplay of a) stand specific factors, particularly different rooting distributions, interception, and throughfall patterns, and b) soil specific factors, particularly different hydraulic conductivity and plant available water fractions under changing environmental conditions. Results show that this interplay between soil and stand specific factors is crucial under dry conditions, while soil specific factors are of minor importance under wet conditions. This contribution will present and discuss results from this data-driven modelling study and provide information about how well processes are represented in these kind of models.

How to cite: Mach, J., Kinzinger, L., Seeger, S., Haberstroh, S., Dubbert, M., Werner, C., Weiler, M., and Orlowski, N.: Combining high-resolution in-situ water isotope measurements with 1D soil hydraulic and transport modelling to understand root water uptake dynamics in a mixed forest ecosystem, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-489, https://doi.org/10.5194/egusphere-egu23-489, 2023.

09:25–09:35
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EGU23-16387
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ECS
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On-site presentation
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Diana Estrella, Martin Mulder, Tom De Swaef, Ruud Bartholomeus, and Sarah Garré

The Flemish coalition agreement 2019-2024 places a strong emphasis on increasing our resilience to drought, including through the active use of resilient zones with (extra) nature to mitigate the effects of climate change. Neighboring agricultural activities can experience positive effects by buffering water in the landscape. However,  too shallow  groundwater levels can have consequences for the workability of the land and the crop growth itself.  This means that farmers and policy-makers do not only need to adapt to an increased occurrence of droughts, but probably also to the impacts of excessive soil water. Therefore, the project PEILIMPACT developed and applied model instruments, adapted to the Flemish conditions, to determine the impact of rising groundwater levels on the yield of common agricultural crops. The model SWAP-WOFOST, part of Water Vision Agriculture as developed for the Netherlands, was used for this purpose together with open data layers available in Flanders. The evaluation framework was based on an extensive literature review of the main points of attention in agriculture. Possible obstacles and concerns from main stakeholders (e.g. farmers) in different regions were also included in the evaluation framework. Results indicate that the impact of soil moisture conditions on crop yields is highly variable, both spatially and temporally. Areas with very shallow groundwater levels (>1 m) are negatively affected in wet years, but benefit in dry years. The opposite occurs in deeper groundwater levels, where more precipitation could compensate for the low groundwater contribution. The final report as well as the model instruments are freely available and documented so that application to specific locations where rewetting projects are planned is possible for all interested parties.  

How to cite: Estrella, D., Mulder, M., De Swaef, T., Bartholomeus, R., and Garré, S.: A modelling framework to estimate the impact of rewetting projects on agricultural activities in Flanders , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16387, https://doi.org/10.5194/egusphere-egu23-16387, 2023.

09:35–09:45
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EGU23-4330
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On-site presentation
Wolfgang Wanek, Denisa Finta, and Erich Inselsbacher

The bioavailability and delivery of nutrients (solutes) to plant roots and soil microbes is governed by diffusive processes. According to Fick’s first law solute diffusion is driven by the diffusivity of the solute, the concentration gradient and the path length. We first shortly review the main factors potentially affecting these drivers i.e. the diffusivity (solute-soil interactions including ion exchange and other sorption reactions, microbial metabolism), the concentration gradient (source-sink relations via mobilization through biotic and abiotic reactions and solute uptake by organisms) and the path length (soil water filled pore space, pore size distribution, texture). Then, based on data synthesis of available microdialysis studies we provide evidence for the ranking of these factors in soils, depending on soil horizon (organic versus mineral soil), fertilization (agriculture versus forests), nutrient form (ammonium versus nitrate versus free amino acids; nitrate versus phosphate) and soil moisture, including drying-rewetting. Microdialysis represents a relatively recent minimal invasive technique for in situ and lab use to measure rates of diffusive solute (nutrient) transport on a microscale level. Since its first application in soil in 2005, this technique has provided unique, non-isotopic and non-destructive insights into major drivers of solute transport in soils, with ~45 studies published thus far.

How to cite: Wanek, W., Finta, D., and Inselsbacher, E.: Fundamental drivers of nutrient diffusion in soils - a comprehensive data synthesis based on microdialysis studies, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4330, https://doi.org/10.5194/egusphere-egu23-4330, 2023.

09:45–09:55
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EGU23-8004
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ECS
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On-site presentation
Chwadaka Pohshna and Damodhara Rao Mailapalli

Excessive phosphorus (P) application through conventional fertilizers to maintain crop yield has increased P pollution and created environmental concerns with serious implications on surface and ground waters. To improve the P nutrient uptake and minimized the undesirable impacts of conventional P fertilizer, nanoparticle such as hydroxyapatite nanoparticle (HANP) was synthesized using the phosphoric acid-treated calcinated chicken eggshells in a planetary ball mill. The synthesized HANP was used as a P nutrient source for lowland rice and the effects on rice agronomical parameters (plant height, tiller count, biomass and yield), P transport and leaching in rice soil with the application of HANP as a P source were studied alongside conventional fertilizer (SSP) and control experiments (CNT) for three seasons (Rabi 2018-19, Kharif and Rabi 2019-20) using field columns. Then the water flow and P transport were simulated with the help of the Hydrus-1D model. The nanoparticles size HANP resulted after 10 hours of milling with a milling speed of 500 rpm and they were observed to be mostly oval in shape with an average particle size of 105 nm. The field column studies indicated an improved plant height, tiller count and yield with HANP and SSP treatment as compared to CNT treatment. No significant difference was observed between HANP and SSP treatment. A significant difference in ortho-P concentration between HANP and SSP treatment was observed in both ponding water and leachate water with higher ortho-P concentrations in SSP as compared to HANP treatment. The simulation results indicated that the Hydrus-1D model successfully simulated the bottom flux and the ortho-P concentration in the leachate very well with a good coefficient of determination (R2), Nash–Sutcliffe efficiency (NSE) and root mean square error (RMSE) values. The value of distribution coefficient Kd was found to be higher in the case of HANP as compared to SSP treatment indicating that more adsorption of P to soil particles occurs in HANP treatment. While the longitudinal dispersivity and the diffusion or precipitation rate constant were approximately higher in SSP treatment than in HANP treatments indicating less local variations in the velocity field of ortho-P in the direction of fluid flow, and a lower dissolution rate of HANP treatment as compared to SSP treatment. Thus the potential of HANP for use as P fertilizer can be demonstrated by the ability to sustain the agronomical parameters of rice crops and the reduced leaching rate and slow-releasing property of the material.

Keywords: Hydroxyapatite, phosphorus, rice, nanofertilizer, Hydrus 1D model

How to cite: Pohshna, C. and Mailapalli, D. R.: Effect of Nanohydroxyapatite in Lowland Rice and Simulation of Phosphorus Transport using Hydrus-1D, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8004, https://doi.org/10.5194/egusphere-egu23-8004, 2023.

09:55–10:05
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EGU23-9076
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ECS
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Highlight
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On-site presentation
Rozita Soltani Tehrani

Transport and retention of fecal indicator bacteria in unsaturated porous media: effect of transient water flow

 

Rozita Soltani Tehrania*, Luc Hornstrab, Jos van Dama, Gijsbert Cirkelb

 

a Department of Soil Physics and Land Management, Wageningen University and Research, P.O. Box 47, 6700 AA Wageningen, the Netherlands
b KWR Water research Institute, Nieuwegein, the Netherlands

 

Email addresses: rozita.soltanitehrani@wur.nl (R. Soltani Tehrani), luc.hornstra@tno.nl (L. Hornstra), jos.vandam@wur.nl (J. van Dam) Gijsbert.Cirkel@kwrwater.nl (G. Cirkel)

 

Abstract

To produce clean drinking water, the processes governing bacterial remobilization in the unsaturated zone at transient water flow are critical. While managed aquifer recharge is an effective way to dispose of pathogens, there are concerns about recontamination after precipitation infiltration. To better understand how bacteria that were initially retained in porous media can be released to groundwater due to transient water content, transport experiments and modeling for Escherichia coli and Enterococcus moraviensis were conducted at the soil column scale. After inoculating dune sand columns with bacteria suspension for 4 h, three rainfall events were performed at 24 h intervals. The effluent from sand columns was collected to analyze bacteria breakthrough curves (BTCs). After the rainfall experiments, the bacteria distribution in the sand column was determined. The collected BTCs and profile retentions were modeled with HYDRUS-1D, using different model concepts: one-site kinetic attachment/detachment (M1), Langmuirian (M2), Langmuirian, and blocking (M3), and two-site attachment/detachment (M4). After inoculation, almost 99 percent of the bacteria remained in the soil, according to the findings of the experiments. The M1 and M2 bacteria models had a high agreement between observed and modeled concentrations, and attachment and detachment were two significant mechanisms for regulating bacteria movement in a porous medium with fluctuations in water flow. At the end of the experiment, the majority of bacteria were still found at the column entrance. Our experiments show that E. coli is more mobile in sandy soils than E. moraviensis. The results of this study suggest that the unsaturated zone is an important barrier between microbial contamination at the soil surface and groundwater. Bacteria that accumulate in the unsaturated zone, on the other hand, can multiply to such an extent that they can be released into the saturated zone when saturation changes due to major rain events or variations in groundwater level. A Follow-up study is needed to completely understand the variables that regulate bacteria remobilization in the unsaturated zone of dune sands.

 

How to cite: Soltani Tehrani, R.: Transport and retention of fecal indicator bacteria in unsaturated porous media: effect of transient water flow, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9076, https://doi.org/10.5194/egusphere-egu23-9076, 2023.

10:05–10:15
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EGU23-12451
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On-site presentation
Wolfgang Durner, Jirka Simunek, and Sascha Iden

In Germany, electricity from the wind power plants in the north must be transported to the south. This is done via underground cables that act as a heat source. We numerically simulated the coupled heating and drying by the cables in the bedding and the surrounding soil under natural boundary conditions. For this purpose, we used a modified version of the Hydrus-2D/3D software code, which enables the coupled modelling of water, vapour and heat flow. The water transport is described with the Richards equation. For heat transport, the processes of heat conduction, convective heat transport and the transport of latent heat are considered. The simulations were carried out in a 2D depth profile oriented orthogonally to the main direction of the cables. The simulations were carried out under atmospheric boundary conditions for the period 2016-2018, the latter being one of the driest years in Germany in recent history.  

We found that warming leads to thermal vapour fluxes that are directed away from the cable, which can significantly reduce the water content of the material near the cable. The lowering of the soil water content reduces the thermal conductivity of the soil and can therefore lead to overheating of the cable with the risk of technical failure. However, the simulations indicate that even under the conditions of 2018, overheating of the cables is unlikely if the bedding material has sufficient thermal conductivity and the spacing between the individual cables is chosen wisely. Crucial for adequate modelling of the water and heat flow was the correct representation of the water retention curve in the dry soil, as the water head in the soil near the cable reaches values down to -105 J kg-1 and soil thermal conductivity changes rapidly at low water contents.

How to cite: Durner, W., Simunek, J., and Iden, S.: Coupled hydrothermal modelling of subsurface heating in the vicinity of high-power power cables under natural conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12451, https://doi.org/10.5194/egusphere-egu23-12451, 2023.

Posters on site: Thu, 27 Apr, 08:30–10:15 | Hall A

Chairpersons: Arno Rein, Giuseppe Brunetti, Jiri Simunek
A.153
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EGU23-10247
Jiri Simunek, Giuseppe Brunetti, Diederik Jacques, Tiantian Zhou, and Miroslav Šejna

In this presentation, we will review version 5 of HYDRUS, which resulted from merging earlier versions of HYDRUS-1D (4.x) and HYDRUS (2D/3D) (3.x), implementing the new integrated form of coupling PHREEQC with HYDRUS (HPx), and including new modules such as Furrow, PFAS, Particle Tracking, Dynamic Plant Uptake, Cosmic, Stable Isotopes, C-Ride, etc. The new HYDRUS GUI dramatically improves graphical capabilities and extends its compatibility to new Windows-based (e.g., 64) bit) operating systems. The new modules and capabilities include: a) the Particle Tracking module (to calculate soil water’s transit times and their frequency distributions), b) the Cosmic module (to calculate cosmic-ray neutron fluxes and to use them to inversely estimate large-scale soil hydraulic properties), c) the Dynamic Plant Uptake (DPU) module (to calculate the translocation and transformation of chemicals in the soil-plant continuum), d) the PFAS module (to consider sorption on the air-water interface and the effects of concentration on viscosity and surface tension, and correspondingly on conductivities and pressure heads), e) the Isotope module (to consider the fate and transport of soil water isotopes with evaporation fractionation, f) the C-Ride module (to consider colloid and colloid-facilitated solute transport), and many other new options and graphical (e.g., two-dimensional z-t graphs of main variables) capabilities. Several nonstandard HYDRUS modules (e.g., accounting for overland flow, freezing/thawing, and alternative root water uptake models) will also be discussed.  

How to cite: Simunek, J., Brunetti, G., Jacques, D., Zhou, T., and Šejna, M.: Numerical Modeling of Vadose Zone Processes using Version 5 of HYDRUS and its Specialized Modules, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10247, https://doi.org/10.5194/egusphere-egu23-10247, 2023.

A.154
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EGU23-7560
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solicited
Tiago Ramos, Hanaa Darouich, Ana Oliveira, Mohammad Farzamian, and Maria Gonçalves

Secondary salinization has long been reported in the Roxo Irrigation District (RID), in southern Portugal, due to use of saline prone irrigation water and the existence of poor structured soils. This study evaluates the soil water and salt budgets in nine commercial orchards located in the RID using the multiple ion chemistry module available in the HYDRUS-1D model during the 2019 and 2020 growing seasons. The study crops were almond, olive, citrus, and pomegranate. The model successfully simulated soil water contents measured in the different fields along two seasons. There was a clear underestimation of the ECe in some fields while simulations of SAR were found to be acceptable. Modeling errors were mostly associated to missing information on fertigation events rather than difficulties in simulating the effect of irrigation water quality on soil quality. The water and salt balances were also computed for the 1979-2020 period. Considering the probability of distribution of salt accumulation during this period, the risk of salt accumulation was very high, except in the citrus areas. The factors influencing the salinity build-up in the study sites were the irrigation strategy, the seasonal irrigation and rainfall depths, the crop growing period, rainfall distribution in the late and non-growing seasons, soil drainage conditions, and irrigation water quality. On the other hand, for current climate conditions and irrigation water quality, the risk of soil salinity levels affecting crop development and yields were found to be minor. Only in two of the study sites, there was the need to promote salt leaching following strategies that differed between locations. This study further aims to promote sustainable irrigation management practices through the better use of soil and water resources in the Alentejo region of southern Portugal.

How to cite: Ramos, T., Darouich, H., Oliveira, A., Farzamian, M., and Gonçalves, M.: Soil salinization risks under current climate and irrigation management in orchards of southern Portugal, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7560, https://doi.org/10.5194/egusphere-egu23-7560, 2023.

A.155
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EGU23-4977
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ECS
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Highlight
Anne Hartmann, Theresa Blume, and Markus Weiler

Form and function are two major characteristics describing hydrological systems and can also be helpful in the context of understanding and analyzing unsaturated flow. Whereas the term “form” summarizes the structure and properties of the system, the term “function” represents the hydrological response. Form parameters such as structural and hydraulic soil properties, but also vegetation cover, have a major influence on the subsurface hydrological response. The combination of different soil and surface properties affects the formation of subsurface hydrological flow paths and their interaction and feedbacks can lead to the formation of preferential flow paths that are difficult to characterize and predict. Little is known about how these characteristics co-evolve over time and how form impacts function in young hydrological systems.

We systematically investigated how form and function evolved during the first 10 millennia of landscape development. We analyzed two hillslope choronosequences in glacial forelands in the Swiss Alps, one developed from siliceous and one from calcareous parent material.
Variables describing form were studied in terms of soil properties and vegetation characteristics obtained by vegetation mapping, extensive soil sampling and laboratory analyses. Variables describing hydrologic function include soil water response times, soil water storage, dominant flow path types, and the frequency of preferential flow paths which were obtained by Brilliant Blue dye tracer irrigation experiments and sprinkling experiments with deuterium. A principal component analysis and clustering were used to identify how form features relate to specific functions.

Our investigation revealed differences in the evolution of form and function between the two different parent materials. At the calcareous site, a change in flow types with increasing moraine age was observed from a rather homogeneous matrix flow to heterogeneous matrix and finger-like flow. However, the high buffering capacity of the calcareous soil leads to less soil formation and fast, vertical subsurface water transport dominates the water redistribution even after more than 10 000 years of landscape evolution. At the siliceous parent material accumulation of organic material with high water storage capacity and podsolization was observed between 3 000 and 10 000 years of landscape development. Under these conditions water redistribution is dominated by vertical subsurface water transport via matrix flow only at young age classes (< 3 000 years). After 10 000 years of soil development vertical subsurface water transport below the organic top layer mainly takes place via macropore flow, and water storage in the organic surface layer and lateral subsurface water transport become the major components controlling water redistribution.

We found that in general the increase in preferential flow frequency is caused by soil development and is further enhanced by an increase in above ground biomass, organic matter and micro topography. Form parameters driving the evolution of subsurface function differ between the two contrasting geologies which highlights the importance of the parent material for landscape development.

How to cite: Hartmann, A., Blume, T., and Weiler, M.: Unsaturated subsurface flow: How it evolves in the first 10 000 years after landscape initialization, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4977, https://doi.org/10.5194/egusphere-egu23-4977, 2023.

A.156
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EGU23-8262
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ECS
Lucy Archibald, Ganesh Khatei, Josh Caplan, Scott Van Pelt, Paolo D’Odorico, and Sujith Ravi

Stormwater control measures (SCMs) such as retention basins, bioswales, and bioinfiltration systems are used to reduce peak flows and remove pollutants from stormwater in temperate urban landscapes. However, the application of de-icing salts to roadways can substantially increase the salinity of stormwater basin media (i.e., engineered soil), likely impacting the physical properties of these soils. Further, SCM soils can become moderately compacted, potentially altering the extent and effects of salinization on soil physical properties. Although many studies have documented the high salinity of roadside soils in winter, the effects of salinity on soil hydraulic properties is not well understood, especially in the context of urban stormwater basins. Here, we compared the water retention properties (spanning pressure potentials of -10 to -1,000,000 hPa) of salinity-affected stormwater media (1-100 dS m-1, using Na+ and Mg2+ salts) that was either uncompacted or compacted. The effects of salinity on both matric and osmotic potential included shifts in the plant-available range with the magnitude depending on a combination of salt type and concentration. We attribute these changes to salinity inducing shifts in both surface tension and pore size distributions. Further, compaction increased the severity of salinization under low salinity conditions but not high. Climate change may increase the number and intensity of snow events in many temperate urban regions, which may increase salt loads to stormwater control measures, exacerbating the aforementioned effects.

How to cite: Archibald, L., Khatei, G., Caplan, J., Van Pelt, S., D’Odorico, P., and Ravi, S.: Compounding Effects of Salinity and Compaction on Hydraulic Properties of Roadside Stormwater Control Measures, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8262, https://doi.org/10.5194/egusphere-egu23-8262, 2023.

A.157
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EGU23-7887
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ECS
Dániel Koch, Fruzsina Kata Majer, Gábor Keve, and Katalin Bene

With the increasingly negative impact of climate change, there is a significant need for more accurate runoff measurements in steep-sloped catchments to understand and predict the impact of extreme weather conditions. The spatial and temporal variability of precipitation, different soil parameters, soil moisture and infiltration characteristics significantly influence the surface runoff and channel flow processes in natural catchments.

During the last 5 years, the Faculty of Water Sciences of the University of Public Service developed a complex meteorological and hydrological monitoring system at Várvölgyi creek which is a 5.95 km2 sub-catchment of Völgységi creek watershed. The small steep-sloped experimental catchment lies on the border of Magyaregregy. This small village located in the eastern Mecsek region in the southern part of Hungary. The research program aims to better understand each runoff process element in the watershed. Five years ago, a meteorological station was installed to improve rainfall measurement accuracy. In addition to meteorological and flow measurements, soil moisture sensors were recently installed at three locations to record soil moisture data at six different depths. In this paper, we investigate the connection between soil water content and streamflow.

The research presented in the article was carried out within the framework of the Széchenyi Plan Plus program with the support of the RRF 2.3.1 21 2022 00008 project.

How to cite: Koch, D., Majer, F. K., Keve, G., and Bene, K.: The connection between soil water content and stream flow in the experimental catchment of Magyaregregy (Hungary), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7887, https://doi.org/10.5194/egusphere-egu23-7887, 2023.

A.158
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EGU23-14720
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Highlight
Daniel Schwindt, Michael Dietze, Jago Jonathan Birk, Simon Drollinger, Adrian Flores-Orozco, and Daniela Sauer

Climate change affects temperate forests particularly by changes in water availability as a result of rising temperatures and changing precipitation dynamics. While the annual mean will remain roughly constant, it is the intensity pattern that will change: light precipitation events decrease and heavy precipitation events increase. Droughts and heat waves are assumed to become more frequent, longer and more intense, also as a feedback mechanism of reduced soil moisture affecting evapotranspiration. In addition to meteorological droughts, edaphic droughts are anticipated to increase in the future. These developments impact the soil hydrological functions with altered infiltration conditions, increased surface runoff and an increasing proportion of preferential flow affecting a more complex and heterogeneous water distribution in the subsurface. Yet the link between tree mortality and the reduced and more heterogenous soil water distribution is still not fully understood

The majority of approaches analysing soil moisture dynamics are based on point measurements, which do not account for the high spatial variability of soil water. Here, we close this knowledge gap by fusing established point-measurements with geophysical methods to assess the spatio-temporal dynamics of water fluxes in the near-surface subsoil from slope to the root zone scale. The questions we ask focus on how infiltration, subsurface water flow, soil moisture distribution and persistence are affected by (i) the subsurface architecture including textural variations as well as preferential flow paths (macro pores, root tracks) and (ii) hydrological extremes (droughts, rain events).

Our study site is located in a beech forest near Ebergötzen (central Germany). The Triassic sandstones are overlain by periglacial slope deposits with varying amounts of loess. The Ebergötzen test site is equipped with numerous sensors for analysing water and element fluxes. In addition to meteorological parameters, we collect 15 min times series of throughfall, stemflow, soil water content, water tension and sap flow. This set-up is ideally suited to quantify water fluxes on a point-by-point basis with high temporal resolution, and to validate complementary, beyond-point approaches. To account for the small-scale variability of processes, geophysical methods with a focus on high-resolution electrical resistivity tomography (Dipole-Dipole, 48 electrodes, 15 cm spacing) were used. Measurements were carried out as a combination of a long-term approach (fortnightly/monthly) and event-based measurements (thunderstorm, round the clock).

Our data indicate a relatively uniform decrease in soil moisture during prolonged dry periods, with root-water uptake locally causing higher dynamics. In contrast, subsurface moisture penetration after precipitation events is spatially highly variable, confirming the importance of preferential flow for infiltration and distribution of water in the subsurface and thus show the high demand for spatially high-resolution measurements of soil moisture dynamics.

How to cite: Schwindt, D., Dietze, M., Birk, J. J., Drollinger, S., Flores-Orozco, A., and Sauer, D.: Spatio-Temporal Water Fluxes in the Slope-Soil-Tree Continuum of a Temperate Beech Forest in central Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14720, https://doi.org/10.5194/egusphere-egu23-14720, 2023.

A.159
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EGU23-11736
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Highlight
Arno Rein, Quanshun An, Yangliu Wu, Dong Li, Xianghong Hao, and Canping Pan

Apple production is a major agricultural activity in many regions around the globe. Over the past decades, a range of different pesticides have been used for preventing fungal and insect infestations. Evaluating the fate of pesticides in plants and soil is important for determining human health risks arising from chemical residues in fruits as well as ecological risks, among others resulting from pesticide fate in soils and eventually leaching to groundwater.

This study aimed at improving the understanding of complex fate and transport processes interacting in the soil-plant system of an apple orchard. Field experiments were done with different insecticides and fungicides that are frequently applied in agricultural practice. Pesticide concentrations in soil and different plant parts were observed at different times under a multiple pesticide applications scenario.  A coupled soil-plant model was set up for numerically simulating pesticide fate and comparison with observed pesticide concentrations. This model considers a tipping buckets approach for soil water and solute transport, linked with a dynamic numerical model for plant uptake and translocation of chemicals within plants, implementing a fruit growth model for explaining the fruit growth dilution. Moreover, risks posed for food safety were estimated.

This model approach was successful for describing observed pesticide residues. Up to 25% of the applied chemicals were deposited on leaves and up to 0.6% on fruits, and up to 61% entered the topsoil directly after application. A decrease in fruit concentration was observed, which could be explained by biodegradation and growth dilution as the main contributions, as well by wash-off. First estimates of dietary risks indicated that the ingestion of the treated apples may not lead to relevant acute or chronic human health risks. The contribution of the different pathways leading to pesticide residues and their dynamics in plant material was highly influenced by precipitation patterns, fruit growth dilution and pesticide characteristics. Our model approach can contribute to an improvement of process understanding concerning the fate of pesticides in apple orchards and pesticide utilization. It has a high potential for supporting decision making with respect to food safety and minimizing risks associated to pesticide use.

How to cite: Rein, A., An, Q., Wu, Y., Li, D., Hao, X., and Pan, C.: Dynamic modeling of plant uptake and leaching of pesticides applied at an apple orchard, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11736, https://doi.org/10.5194/egusphere-egu23-11736, 2023.

A.160
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EGU23-17163
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ECS
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Sebastián Bravo Peña, José Dörner, and Loes van Schaik

Predicting the spatiotemporal variability of soil moisture dynamics at different scales is a major challenge. Moreover, multimodal soil hydraulic properties resulting from complex soil structures, such as the exhibited by volcanic soils, still lack realistic and dynamic parameterisation. This work aimed to shed light on the spatiotemporal heterogeneity of subsurface water flows and soil water distribution during wet and dry conditions in volcanic ash-derived soil. The volumetric moisture content (VMC) at 10, 20, and 60 cm depth was measured with a set of eight TDR sensors from September 2019 to January 2022 with a 10-minute resolution. These VMC time series were separated into wet (WP) and dry (DP) periods based on the mean VMC. Subsequently, the spatiotemporal variability in moisture content within the soil profile was analysed using spectral analyses. The propagation of periodicities from Prate to the three topsoil VMC time series as well as the time scales in the correlation of the VMC between sensors were described. Finally, the time dependency of wetting slopes (St) on Prate was assessed by the cross-correlation function (CCF). The VMC dynamics vary between WP and DP, related to the water-filled pore space and pore size distribution. The CWT showed that Prate periodicities propagate to VMC, except for periodicities of 3 to 6 months scales. The WC showed that increases in VMC result in an exponential decrease in the minimum time scale of correlation between moisture contents measured within the topsoil. The CCF described a moderate temporal correlation between Prate and St. The soil wetting response to precipitation was notably faster during wet periods, while the cross-correlation lag and the response heterogeneity increased during dry conditions. The heterogeneity of subsurface water flows resulting from complex soil structure dynamics were described by the spatiotemporal variability of soil moisture in volcanic ash- derived soil. VMC response to Prate is faster during wetter conditions than in dry periods. Temporal periodicities within the topsoil suggest that hydraulic properties experience a dynamic shift from a heterogeneous to a homogeneous system. Changes in the temporal correlation of the soil moisture measured within the topsoil, along with an accurate description of the time dependency of St on Prate, can be valuable for further understanding the hysteresis of soil moisture variations in a soil profile.

How to cite: Bravo Peña, S., Dörner, J., and van Schaik, L.: Influence of soil structure on the spatiotemporal variability of subsurface water flows in a volcanic ash-derived soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17163, https://doi.org/10.5194/egusphere-egu23-17163, 2023.

A.161
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EGU23-11132
Sascha Iden, Johanna Blöcher, Efstathios Diamantopoulos, and Wolfgang Durner

Evaporation from bare soil is an important hydrological process and part of the water and energy balances of land surfaces. Comprehensive modelling of this process must include coupled liquid, vapor and heat fluxes. Model concepts of varying complexity have been proposed to predict water loss from soil through evaporation. The objective of our study was to test a coupled water, vapor and heat flow model with data from laboratory evaporation experiments under different boundary conditions. Laboratory evaporation experiments were conducted with a sand and a silt loam under three atmospheric forcings. Pressure heads, soil temperature and the evaporation rates were monitored and the experiments were simulated with a coupled water, vapour and heat flow model which solves the surface energy balance and predicts the evaporation rates. The evaporation dynamics was well captured, in particular the onset of stage-two evaporation and the evaporation rates during stage-two. A valid description of the observed data required the use of a comprehensive model of the soil hydraulic properties which accounts for water adsorption and film flow. However, a slow continuous decrease in the measured evaporation rate during stage-one could not be described with the model under the assumption of a constant aerodynamic resistance. While the addition of established empirical soil resistance parametrizations significantly degraded model performance, the use of a boundary layer resistance improved the evaporation rate predictions for the sandy soil but not for the silt loam. Care should be taken when using resistance parametrizations in coupled modelling of bare soil evaporation.

How to cite: Iden, S., Blöcher, J., Diamantopoulos, E., and Durner, W.: Validation of coupled water, vapor and heat flow models with evaporation experiments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11132, https://doi.org/10.5194/egusphere-egu23-11132, 2023.

A.162
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EGU23-16234
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ECS
Francesca Lobina, Stefania Da Pelo, Christine Stumpp, Claudio Arras, Riccardo Biddau, Antonio Coppola, and Andrea Vacca

In recent years, with the development of intensive farming and livestock breeding activities, nitrate contamination of aquifers has occurred. The importance of the unsaturated zone in the study of nitrate percolation is well recognized. The vadose zone represents a fundamental part of the water cycle, capable of storing water, providing water for vegetation, transporting solutes and degrading contaminants before they reach the aquifer.
This research involves two areas with different geological, hydrogeological and pedological properties located in Sardinia. The plain of Arborea has been designated as Nitrate Vulnerable Zone (NVZ) since 2005, but despite the reduction of nitrogen input no significant improvement in water quality has been achieved. In the Southern Campidano plain, an area with an agricultural tradition, significant nitrate concentrations were observed in groundwater.
The main objective of this research is to estimate the groundwater recharge rate using vadose-zone water stable isotope profiles.
Firstly, to understand the dynamics of water percolation through the vadose zone, soil samples were collected at different depths to analyzed for physical properties, including soil-water content, and grain size to estimate soil hydraulic properties. In addition, suction cups were installed at different depths at each site to extract pore water from the soil for chemical analysis.
In hydrological systems, the use of stable isotopes (18O and 2H) of pore water as environmental tracers is considered the most useful tool for establishing water flow and contaminant transport. In this study stable pore water isotope profiles combined with water content profiles were used to obtain insight into the transit time of water percolating through the vadose zone. At each of the two study sites, vertical soil sampling was made along the vadose zone and the soil samples collected were analyzed for stable water isotope ratios (18O and 2H) and volumetric water content. Through the seasonal signatures of stable isotopes in leachate water it is possible to quantify possible groundwater recharge, this approach, called the peak-shift method assumes advection-dominated transport.
Analysis of nitrate concentrations in soil water below the root zone using suction cups combined with groundwater recharge rates will allow an estimate of site-specific nitrate leaching. Through this approach, it is possible to evaluate potential and conservative propagation of nitrogen at specific depths to be compared with the concentrations measured to gain information on nitrate transformation processes in the soil.

How to cite: Lobina, F., Da Pelo, S., Stumpp, C., Arras, C., Biddau, R., Coppola, A., and Vacca, A.: The use of stable pore water isotopes in the study of nitrate leaching, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16234, https://doi.org/10.5194/egusphere-egu23-16234, 2023.

A.163
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EGU23-4060
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ECS
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Saurabh Kumar and Richa Ojha

Soil hydraulic properties exhibit spatio-temporal variability and are affected by both natural and human factors. Their knowledge is essential for assessing soil water regimes. Scaling methods based on similar media concept have been widely used to model the surface spatial and temporal variation of vadose zone processes while assuming that similarity conditions are preserved. Soil heterogeneity, changes in field conditions due to rainfall or irrigation and other factors lead to changes in boundary conditions which makes analysis based on similitude analyses or functional normalization difficult. However, inspectional analysis method can reduce known physical laws along with corresponding initial or boundary conditions to non-dimensional form while eliminating as many physical constants and variables as possible which is then used to obtain scale factors and similarity requirements. The objective of this study is to obtain scaling factors based on inspectional analysis to describe the temporal variability of soil hydraulic properties.

How to cite: Kumar, S. and Ojha, R.: Use of Scaling to Describe Temporal Variability of Soil Hydraulic Properties, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4060, https://doi.org/10.5194/egusphere-egu23-4060, 2023.

A.164
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EGU23-3205
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ECS
Alexander Sternagel, Ralf Loritz, and Erwin Zehe

We develop an integrated model framework for the simulation of a multitude of soil hydrological processes, such as (reactive) solute transport together with (preferential) water flow and diffusive mixing on the pore scale. This framework is called the Lagrangian Soil Water and Solute Transport (LAST) Model. It bases on a new theoretical concept and should serve as alternative to the common theories of the Darcy-Richards equation and the advection-dispersion-equation (ADE), which have limitations under more natural conditions.

In the LAST-Model framework, soil water is represented by discrete water particles of constant mass. The model applies a Lagrangian perspective on the trajectories of particles through a partially saturated soil domain. Particle displacements along the trajectories are calculated by a non-linear, space domain random walk that combines physics and stochastic. We gradually extend the scope of the LAST-Model framework by additional routines.

We implement routines for solute transport and preferential flow. Water particles are assigned by a solute mass and in this way, solutes are distributed together with the displacement of water particles. For preferential flow, a structural macropore domain is implemented as a second flow domain. Particles can infiltrate and travel purely by gravity in the macropore domain, independent from capillary-flow conditions in the soil matrix. As a result, they can bypass the bulk water fractions in the soil matrix before re-infiltrating the matrix and accumulating in greater depths.

We modify the solute transport routine to allow for the simulation of the transport of reactive substances. Specific routines for sorption and degradation processes are implemented. Sorption is represented by an explicit solute mass transfer between water particles and the solid phase by means of non-linear Freundlich isotherms, and driven by a concentration gradient. Adsorbed solutes are then assumed to be microbially degraded following first-order decay kinetics.

We introduce the diffusive pore mixing (DIPMI) approach as additional routine for the simulation of pore-size-dependent diffusive mixing of water and solutes over the pore space. This approach should produce more reliable descriptions of frequently observed (imperfect) mixing behaviours, in contrast to the common assumption of averaging concentrations over all pore sizes in a single time step.

Each model extension is tested by simulations of field and laboratory experiments as well as sensitivity analyses. Simulation results are compared against observed data and results of a benchmark model that uses the Darcy-Richards theory and the ADE. The most important findings of the studies can be summarized as:

  • The structural macropore domain is key for a successful representation of preferential water flow and (reactive) solute transport. In heterogeneous soils, LAST simulations match better the observed redistribution and depth-accumulation of solutes compared to simulations with the Darcy-Richards + ADE model.
  • Imperfect, diffusive mixing on the pore scale has a significant influence on macroscopic leaching behaviours and chemical/isotopic compositions of soil water fractions.
  • The particle-based approach of the LAST-Model framework is a promising tool for further soil- and ecohydrological application fields.

How to cite: Sternagel, A., Loritz, R., and Zehe, E.: A Lagrangian model framework for the simulation of fluid flow and solute transport in soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3205, https://doi.org/10.5194/egusphere-egu23-3205, 2023.

A.165
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EGU23-5867
Heejun Suk, Jize Piao, Weon Shik Han, and Seong-Kyun Kim

A new numerical method was developed to accurately and efficiently compute a solution of the nonlinear Richards equation with a layered soil. In the proposed method, the Kirchhoff integral transformation was applied. However, in the Kirchhoff integral transformation approach, the transformed Kirchhoff head has dyadic characteristics at the material interface between different soil types. To avoid the dyadic characteristics at the material interface, a truncated Taylor series expansion was applied to the Kirchhoff head at the material interface and so the Kirchhoff head was replaced with a single pressure head value at the material interface. Accordingly, through the Taylor series expansion, a set of algebraic equations in the one-dimensional control volume finite difference discretized system formed a tridiagonal matrix system. Through a series of numerical experiments, the new method was compared to other numerical methods to determine its superiority. The results clearly demonstrated that the approach was not only more computationally efficient, but also more accurate and robust than other numerical methods. Computational performance was greatly enhanced with the proposed method, and which could be used to simulate complicated heterogeneous flow at a large-scale watershed or regional scale.

Acknowledgments

This work was supported by the basic research project (23-3411) of the Korea Institute of Geoscience and Mineral Resources (KIGAM) funded by the Ministry of Science and ICT.

How to cite: Suk, H., Piao, J., Han, W. S., and Kim, S.-K.: Numerically efficient algorithm for simulating variably saturated flow in heterogeneous layered porous media, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5867, https://doi.org/10.5194/egusphere-egu23-5867, 2023.

A.166
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EGU23-5902
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ECS
Zhi Li, Daniel Caviedes-Voullième, and Ilhan Özgen-Xian

Catchment-scale hydrological simulations typically require numerical solutions to the Richards equation, which describes variably-saturated water flow in porous media. In recent years, with the widespread use of high-performance computing (HPC), the simulation speed of hydrological models have been significantly enhanced. However, existing numerical schemes for the Richards equation show different performance under different HPC configurations. It remains unclear if the serial Richards solvers scale well in parallel. 

In this work, four popular numerical schemes (the fully explicit scheme, the predictor-corrector scheme, the iterative Picard scheme, and the fully implicit Newton's scheme) are implemented to solve the three-dimensional Richards equation, aiming at investigating the performance of these schemes on both multi-core CPUs and GPUs. The codes are built under the Kokkos framework to achieve performance portability between CPU and GPU. Two infiltration problems with analytical solutions available are chosen to evaluate the model performance in terms of accuracy and efficiency. 

As expected, the simulation results indicate that the optimal solution schemes on CPU and GPU could be different. Moreover, the numerical scheme, the linear system solver, and the soil properties all have influence on scaling. A hybrid scheme is promising for minimizing the computational cost under various simulation conditions. The findings of this work will guide the development of the subsurface flow module of the performance-portable, multi-physics model, SERGHEI.

How to cite: Li, Z., Caviedes-Voullième, D., and Özgen-Xian, I.: GPU-accelerated numerical solution to the Richards Equation:performance and prospects, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5902, https://doi.org/10.5194/egusphere-egu23-5902, 2023.

Posters virtual: Thu, 27 Apr, 08:30–10:15 | vHall HS

Chairpersons: Arno Rein, Giuseppe Brunetti, Jiri Simunek
vHS.24
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EGU23-4476
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ECS
Andreea Aurelia Iojă and Daniel Scrădeanu

Ignored until now for their hydrogeological potential, in the conditions of current climate changes, the Sarmatian deposits in the Moldavian Platform, Romania attract the attention of researchers aiming at the objectives of Romania's long-term security strategy. Vital resource, underground water, significantly affected by global climate changes, calls for regional management strategies that must be based on detailed hydrogeological research of storage, recharge and protection conditions under the impact of natural and anthropogenic factors.

Integration of contaminant migration is the current, highly effective approach for evaluation of groundwater resources used as the source of tapping groundwater supplies for a large part of urban and rural agglomerations.

The Sarmatian hydrostructures from the Moldavian Platform, with a high level of vulnerability to pollution, are the subject of our integrated hydrogeological modelling, in which the vadose zone is the main complex objective. Using our Integrated Hydrogeological Modelling we achieved the coupling of the contamination migration from the soil, the vadose zone and the phreatic Sarmatian hydrostructure in several areas (Huși, Vaslui, Botoșani).

The quantitative evaluations carried out on the conceptual 3D models of the SARMATIAN hydrostructures were carried out using the classic tools: ROCKWORKS, SESOIL, VS2DT, MODFLOW.

How to cite: Iojă, A. A. and Scrădeanu, D.: An Integrated Hydrogeological Modelling Approach to Evaluate Groundwater Resources of Sarmatian Hydrostructure from the Moldavian Platform, Romania, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4476, https://doi.org/10.5194/egusphere-egu23-4476, 2023.