HS8.3.1 | Vadose zone hydrology: advances and future perspectives in soil hydrologic processes
Vadose zone hydrology: advances and future perspectives in soil hydrologic processes
Co-sponsored by ISMC, ICID, and ICARDA
Convener: Roland Baatz | Co-conveners: Mira Haddad, Sara Bonetti, Martina Siena, Marco Peli, Stefano Barontini, Stefano Ferraris
Orals
| Tue, 25 Apr, 16:15–18:00 (CEST)
 
Room 3.16/17, Wed, 26 Apr, 08:30–10:15 (CEST), 10:45–12:30 (CEST)
 
Room 3.16/17
Posters on site
| Attendance Wed, 26 Apr, 16:15–18:00 (CEST)
 
Hall A
Posters virtual
| Attendance Wed, 26 Apr, 16:15–18:00 (CEST)
 
vHall HS
Orals |
Tue, 16:15
Wed, 16:15
Wed, 16:15
This session aims to bring together scientists advancing the understanding of vadose zone hydrology from the pore- to the catchment- and continental scale. Modeling and observation of vadose zone processes aims at characterizing soil properties, quantifying vadose zone water fluxes including exchange with aquifers and surface waters and feedbacks within the soil-vegetation-atmosphere continuum. The states of soil, air and water in the vadose zone affect soil biogeochemical processes, vegetation water availability, nutrient and pollutant transport at local scale, catchment response functions and rainfall-runoff processes at intermediate scale, land-atmosphere interaction and land-climate feedbacks at the continental scale. Recent continental-scale drought events urge the need for improved vadose zone process understanding and it challenges current process descriptions and parameterizations in modelling the vadose zone. 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.
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: Tue, 25 Apr | Room 3.16/17

Chairpersons: Marco Peli, Roland Baatz, Mira Haddad
16:15–16:20
16:20–16:30
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EGU23-9991
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On-site presentation
John R. Nimmo

Low-water content soil moisture relations are increasingly important given current trends of climate change, desertification, and growing interest in extreme environments like those of Antarctica and Mars. Whereas most parametric models of soil water retention were developed for the intermediate and wet ranges of moisture, some alternatives published in the last three decades address water retention down to oven dryness. Such models can be strengthened and made more versatile with a deeper understanding of the physical meaning of parameters used in them.

For the shape of the dry-range retention curve, a logarithmic relation has repeatedly been shown to work well, and is consistent with accepted theories of adsorption. Fitted values of the log function’s coefficient relate closely to the specific surface area of the medium.

The lower limits of water content and matric potential require more explication. Various observers have noted problems that arise with the use of a nonzero residual water content as the lower limit. In practice, this quantity is not measured but obtained as a fitting parameter, whose value depends not on a physical property but on how far the available measurements extend into the dry range. In parametric models it can be useful for applications in which the water content never goes below the intermediate range dominated by capillary processes.

The actual lower limit of water content depends on how its zero is defined. The most common definition is based on equilibration in an oven at a particular temperature, commonly 105° C. Ambiguity arises from the dependence of the soil water on the generally uncontrolled relative humidity within the oven. Application of the Kelvin equation with reasonable assumptions about the outside air and its exchange with the inside air can indicate an equivalent matric potential of the oven-dry state, typically about -1 GPa. Logarithmic extrapolations of dry-range retention measurements intersect the water content=0 axis at values comparable to this, with variations likely related to particular conditions in the lab and oven. A way of resolving this ambiguity is to define zero water content not in terms of oven temperature but rather a specified matric potential of equilibration. An attractive possibility, convenient in SI units, is to make it exactly -1 GPa.

Neither the traditional nor this proposed definition of zero water content identifies a state where no water molecules remain in the soil. Measurements at temperatures of hundreds of degrees C show that soil water contents can be lower than these defined zero levels by as much as 2% or more. Our standard scale of water content, therefore, is a relative scale, analogous to the Celsius scale for temperature. Consequently negative values of soil water content have a valid physical meaning. To acknowledge this fact and resolve ambiguities, more rigorous definitions as proposed here are thus necessary for applications dealing with the extremely dry conditions that are becoming increasingly important.

How to cite: Nimmo, J. R.: Soil water retention parameters in the dry range—what is the physics?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9991, https://doi.org/10.5194/egusphere-egu23-9991, 2023.

16:30–16:40
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EGU23-1485
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ECS
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On-site presentation
Davide Gisolo, Mesmer N'sassila, Alessio Gentile, Francesca Pettiti, Mattia Barezzi, Umberto Garlando, Luca Nari, Stefano Ferraris, Danilo Demarchi, and Davide Canone

The WAPPFRUIT project is related to the optimisation of irrigation techniques in the Piemonte Region, Northwest Italy. The main goal is to control irrigation to understand if it is possible to reduce the volume of water used for irrigation and also save energy. The project involves several stakeholders, among which Politecnico and the University of Torino, Piemonte Region, Agrion Foundation for research in agriculture, and three farms (two apple orchards and one Actinidia orchard). The optimisation relies on soil matric potential measurements at several soil depths. The irrigation will be triggered using a particular algorithm which is based on a system of matric potential thresholds at the depths of 20 and 40 cm. These thresholds are based on soil texture, and vegetation species (including root depth). 

Each orchard is divided into two parts: an “experimental area” where the irrigation algorithm will be tested, and an area that will be irrigated as usual by farmers. Each orchard is equipped with four to six measurement nodes, with soil water content and soil matric potential profile having measures at 20, 40, and 60 cm of depth. 

The retention curves, as well as the spatial and temporal variability of soil water content and soil matric potential, can be inferred from measures, which reveal high volumes of water used for irrigation (frequently the soil was near saturation conditions). In addition, all the soils show, in the retention curves, a hysteresis due to wetting/drying cycles. 

The farmers continued to irrigate as usual in the two parts of the fields up to October 2022. Hence, to investigate the matric potential behavior and identify good estimates of thresholds, modeling approaches are important for the simulation of soil without irrigation, to understand when water stress conditions could occur. To this purpose, two models are used to simulate the water fluxes in the atmosphere and the soil (and, particularly, the matric potential). The two models adopted are the hydrological model Hydrus 1D and the land-surface model CLM5. Forcing the models with the precipitation summed to irrigation of the fields, Hydrus, in its 1D formulation did not yield reliable results, although more studies are needed to fully understand the causes for the misrepresentation. The CLM model yields instead more reliable outcomes. The CLM model is then used to simulate the behavior of the soil matric potential under the hypothesis of no irrigation. The results illustrate that the matric potential threshold for triggering irrigation could be around -50 kPa at 20 cm, whereas the threshold at 40 cm for the deactivation of irrigation could be around -40 kPa for the sites with apple orchards. The site with Actinidia could have the aforementioned thresholds equal to -40 kPa at 20 cm and -30 kPa at 40 cm.

How to cite: Gisolo, D., N'sassila, M., Gentile, A., Pettiti, F., Barezzi, M., Garlando, U., Nari, L., Ferraris, S., Demarchi, D., and Canone, D.: Wappfruit: a project for the optimisation of water use in agriculture, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1485, https://doi.org/10.5194/egusphere-egu23-1485, 2023.

16:40–16:50
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EGU23-9560
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ECS
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On-site presentation
Ana Claudia Callau-Beyer, Martin Mburu, Caspar-Friedrich Weßler, and Hartmut Stützel

Irrigation and fertilization are essential to increasing crop yield and affect vegetable production and food security. Conventional irrigation and fertilizer application methods often exceed the crop requirements. Moreover, nitrate pollution of groundwater from agriculture is caused by the asynchrony between nutrient availability and crop demand and is an issue of major concern in many regions. As water and nutrients limitations will be more frequent in the coming decades due to climate change along with regulations aiming at protecting water resources, there is a need for innovations in agricultural production to improve water and nutrient use efficiencies. Subsurface drip fertigation (SDF) is the fertigation (irrigation combined with application of dissolved fertilizer) of crops through buried driplines which include built-in emitters to drip water to the surrounding soil. This allows placing the water and fertilizers directly into a small soil volume in the rooting zone at just the rates needed by the plants. SDF systems have a great potential to minimize the movement of water and nutrients below the root zone when effectively managed. Through the combined application of nutrients and water, drought and nutrient stresses can be diminished and yield potentials optimized. SDF systems can therefore make cropping systems not only more environmentally friendly and sustainable, but also more resilient to climatic fluctuations.

The aim of our research is to contribute to the understanding of crop growth under SDF. The work presented here is the Subsurface Drip Fertigation Estimation Tool (SubFerT) which is available for farmers who want to integrate this fertigation system in their production. The tool is based on daily water and nitrogen balances at the field scale by modeling (a) crop growth and nitrogen uptake; (b) crop water requirements though daily ET0 estimation using the Penman–Monteith equation, separation between evaporation and transpiration (dual Kc approach); (c) dynamics of water (irrigation, precipitation, root uptake, losses) and nitrogen (mineralization, denitrification, leaching) in the soil root zone. SubFerT-tool provides information on when and how much water and fertilizer to apply to crops grown under SDF system. This tool allows farmers to manage the fertigation of the crops under SDF in an efficient way. Additionally, the tool delivers daily time series of different variables involved in the balance: soil moisture, root uptake, deep percolation, total met transpiration, etc.

How to cite: Callau-Beyer, A. C., Mburu, M., Weßler, C.-F., and Stützel, H.: Subsurface drip fertigation estimation tool (SubFerT), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9560, https://doi.org/10.5194/egusphere-egu23-9560, 2023.

16:50–17:00
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EGU23-15914
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On-site presentation
Yunqiang Wang and Shaozhen Liu

A distinct greening trend is evident in Asia, especially on the Chinese Loess Plateau (CLP), which is driven by climate change and human-induced revegetation projects, such as the Grain for Green (GFG) project launched in 1999. However, revegetation may cause below-ground soil drought via excessive consumption of deep soil moisture (SM). To ascertain the contributions of revegetation projects to the greening trend on the entire CLP, and then evaluate the spatial-temporal variations of soil drought, as indicated by the dried soil layer (DSL), we collected multisource satellite datasets from 1982 to 2019 on the CLP and measured SM to a depth of 500 cm on 20 occasions at 73 locations from 2013 to 2016 at a typical watershed. We found that the revegetation project failed initially to make a positive contribution in the first few years because of the drought conditions in 1999-2005; after 2005, the increasing trend of vegetation change on the CLP indicated that the revegetation project, as a type of external disturbance, began to improve vegetation growth, meanwhile the increased precipitation played a critical role. The contribution of the revegetation projects increased quickly until 2013, after which it remained stable and reached average values of 58.8%±19.34% in the representative areas that conducted the GFG project. The DSLs occurred at > 90% of the sampling sites within the watershed, and the spatially and temporally averaged DSL thickness (DSLT) and soil water content within the DSL (DSL-SWC) were 257 cm and 10.4%, respectively, which suggests that 51.4% of the 500-cm-profile is drying out below 125 cm. The DSLT and DSL-SWC demonstrated a moderate degree of variability (20% < CV < 84%) in space, and showed a moderate and weak temporal variability, in time, respectively. The temporal series of the mean spatial DSLT significantly correlated with climatic variables. The spatial variation of the mean temporal DSL-SWC differed significantly among the land uses and between shaded and sunlit aspects. Our results highlighted that the meteorological processes, land use, and topography played an essential role in shaping DSL variation and distribution pattern. Understanding this information is helpful for vegetation construction, soil and water conservation, and soil drought meditation via the best management practices in the CLP and other water-limited regions with deep soils.

 

How to cite: Wang, Y. and Liu, S.: Dynamics of deep soil drought triggered by revegetation across a semiarid watershed, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15914, https://doi.org/10.5194/egusphere-egu23-15914, 2023.

17:00–17:10
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EGU23-3760
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ECS
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On-site presentation
Ya-Zhen Huang and Chihhao Fan

Agriculture is vital for human survival and irrigation water quality plays an important role in agricultural growing and harvest. Although Taiwan has abundant rainfall, the uneven distribution of rainfall in time and space makes the irrigation water management difficult. In the past two decades, climate change has led to frequent occurrence of extreme weather events and global disasters, and the increase in the frequency and intensity of extreme events enhances the potential disaster risk in Taiwan, impacting the water resource management severely. Meanwhile, industrial wastewater is a significant pollution source, and the surface water quality would be further deteriorated if the industrial wastewater was not treated properly before its release. In Taiwan, the needs of water resources for domestic and industrial uses have the higher allocation priority than that for agricultural use, considering the political concerns and economical contribution. Oftentimes, a supplementary water resource to meet irrigation need is required due to the scarce of available water resources. The situation may become even worse under the influence of climate change.

Given the information above, this study explored the irrigation water quality variation under the influence of climate change on agricultural water resource management. The Taoyuan City (including Taoyuan irrigation Shimen irrigation areas) were selected as the study area. The potential impact of climate change on irrigation water quality, considering factors of pollution discharges and economic development, was assessed. Adaptive strategies including stabilizing irrigation water demand, strengthening irrigation water supply and building an agricultural technology auxiliary system were discussed. The result showed that the increasing frequency of heavy rainfall events in Bade, Xinwu, and Guanyin Districts. The surface pollutant would be washed out easily during heavy rainfall events, impacting neighboring water bodies. On the other hand, drought events appear in Daxi and Fuhsing Districts in extreme climate events. Therefore, a new strategy for sustainable water management is needed.

How to cite: Huang, Y.-Z. and Fan, C.: Irrigation water quality management under the impact of climate change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3760, https://doi.org/10.5194/egusphere-egu23-3760, 2023.

17:10–17:20
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EGU23-2861
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ECS
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On-site presentation
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Niccolò Renzi, Lorenzo Villani, Hilali Muhi El-Dine, Mira Haddad, Elena Bresci, Stefan Strohmeier, and Giulio Castelli

In drylands, agriculture is mainly rainfed due to the absence of water resources for irrigation. In such contexts, water harvesting interventions have been part of the knowledge and legacy of the local communities for centuries. In the Jordanian Badia, research centres like ICARDA (the International Centre for Agriculture Research in Dry Area) have tried to improve this knowledge and have developed several experiments to increase local communities’ livelihood by introducing up-to-date water management practices.

This study focused on the modeling one of these interventions, the Marab Water Harvesting technology (WHT), a macro-catchment water harvesting system that gets flooded by the run-off of the upstream watershed, increasing the water infiltrated and stored in the soil. This water buffer enhances barley production, hence more fodder is available for the local livestock, allowing the communities to reduce the grazing pressure on their lands.

AquaCrop by FAO was used to simulate the crop cycle. The data needed to run the simulations were collected in fieldwork in the Jordanian Badia during the cropping season 2021/2022. Satellite images were also used to improve the calibration and validation process, together with yield data. Different scenarios were run to assess the performance of the Marab WHT, considering: comparison with the traditional cropping technique, flooding events reduction, different soil textures, and different climatic conditions.

The results of the simulations were: i) barley produced more in the Marab WHT (8.13 t/ha) rather than with the traditional cropping technique (between 0.00 - 1.00 t/ha;  ii) silty soils were the most productive with 9.25 t/ha of biomass production, while the least productive had been the clay soils with 6.60 t/ha; iii) with a changing climate, the Marab WHT started to reduce its production by 4-8 % with a +0.5°C temperature increase. In contrast, the reduction of precipitation didn’t impact significantly the crop, decreasing the yield by only 4 – 10%. In fact, the main cause of the high crop yield reduction was the timing and numbers of the flood events, causing barley failure if both the first and last flood events are removed. Without the first flood, the yield decreases by up to 80%, while removing the last flood event the reduction in biomass is 50%.

 

How to cite: Renzi, N., Villani, L., Muhi El-Dine, H., Haddad, M., Bresci, E., Strohmeier, S., and Castelli, G.: Modeling of Indigenous Marab Water Harvesting Technique in the Jordanian Badia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2861, https://doi.org/10.5194/egusphere-egu23-2861, 2023.

17:20–17:30
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EGU23-12328
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ECS
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On-site presentation
Giulio Luca Cristian Gilardi, Alice Mayer, Michele Rienzner, Giovanni Ottaiano, Darya Tkachenko, Marco Romani, Elisa Cadei, and Arianna Facchi

The north-western part of the Padana Plain in Italy is the most important rice district in Europe. Recently, due to an increased frequency of water scarcity periods, the traditional wet seeding and continuous flooding irrigation has been replaced by dry seeding followed by a delayed flooding or by a turned irrigation. Despite the advantages that dry seeding has brought to farmers, this change is leading to unexpected problems, the main of which are: i) the lowering of groundwater levels in the first months of the agricultural season that is reducing groundwater contribution to water discharges in rivers and irrigation networks of the area, limiting the water availability for agricultural areas downstream; ii) a shift to June of the maximum rice irrigation requirement, leading to an exasperated competition between rice and other crops (e.g. maize).

In the contest of the MEDWATERICE (PRIMA Section2-2018) and RISWAGEST project (Regione Lombardia, RDP 2014-20), an experimental platform was set up in the core of the Italian rice area (Mortara, PV) to compare three rice irrigation strategies in the period 2019-2022: i) wet seeding and traditional flooding (WFL), ii) dry seeding and delayed flooding (DFL) and iii) wet seeding and alternated wetting and drying (AWD). Irrigation water use was monitored and all the other soil water balance components were quantified. At the field scale, irrigation use was found to be in the order: WFL > DFL > AWD, without penalizing rice production, while the temporal distribution of irrigation needs and percolation fluxes (i.e. groundwater recharge) changed as a function of the irrigation strategy.

Results achieved in the experimental platform were used to set-up a semi-distributed agro-hydrological model simulating water fluxes and storages of a rice irrigation district (about 1000 ha) close to the experimental platform. The modelling framework consists of three sub-models: i) one for the agricultural area, based on the physically-based SWAP (https://www.swap.alterra.nl/); ii) one for the channel network percolation; iii) one for the groundwater level dynamics. Once calibrated, the modelling system was used to explore the effects on the water resources of ‘what-if scenarios’ based on the adoption of specific irrigation strategies in the whole rice-cropped area of the district (about 90% of the agricultural surface) for the period 2013-2020. Besides the aforementioned WFL, DFL and AWD, the following strategies were additionally explored: i) dry seeding and fixed irrigation turns of 8 days (FTI) and ii) early seeding for the DFL irrigation technique (beginning of April). Three indicators were used to support the analysis: i) Water Application Efficiency - WAE, defined as the potential evapotranspiration divided by the irrigation reaching the fields plus rainfall, ii) Distribution Efficiency of the irrigation network - DE, defined as the irrigation reaching the fields divided by the irrigation discharge entering the district, iii) Relative Water Supply - RWS, defined as the irrigation discharge entering the district plus rainfall divided by the potential evapotranspiration. Water fluxes and indicators are calculated and discussed both for the entire agricultural season (April-September) and for the most critical month (June).

How to cite: Gilardi, G. L. C., Mayer, A., Rienzner, M., Ottaiano, G., Tkachenko, D., Romani, M., Cadei, E., and Facchi, A.: Modelling the impact of Alternate Wetting and Drying (AWD) rice irrigation on water resources in northern Italy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12328, https://doi.org/10.5194/egusphere-egu23-12328, 2023.

17:30–18:00

Orals: Wed, 26 Apr | Room 3.16/17

Chairpersons: Sara Bonetti, Roland Baatz, Stefano Ferraris
08:30–08:35
08:35–08:45
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EGU23-17595
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solicited
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On-site presentation
Tobias K. D. Weber

Hydro-pedotransfer functions (hyPTF) are important methods to relate available knowledge about soil properties to soil hydraulic properties and model parameters to be applied in process models. At least more than four decades have been invested to derive such relationships. However, while models, methods, data storage capacity, and computational efficiency have advanced, there are fundamental issues related to the scope and adequacy of current hyPTFs, particularly when applied to parameterise models at the field scale and beyond. Much of the hyPTF development process has focussed on refining and advancing the methods, while fundamental questions remain largely unanswered, namely i) how should hyPTFs be built for maximum prediction confidence, ii) which processes/properties need to be predicted to move beyond the van Genuchten-Mualem based parameterisation of the Richards equation, iii) which new datasets and data coverage are needed, iv) how does the measurement process of soil hydraulic properties determine the construction of hyPTFs and at which scale, iv) how can we incorporate diverging scales (scale of derivation vs scale of application), and v) what scaling/modulation/constraining strategies are affective to make hyPTF predictions at field-to-regional scale appropriate and physically meaningful? These questions have been addressed in a joint effort by the members of the International Soil Modelling Consortium (ISMC) Pedotransfer Functions Working Group with the aim to systematise hyPTF research and provide a roadmap guiding scientists, reviewers, and make users aware of the shortcomings.

How to cite: Weber, T. K. D.: Hydro-pedotransfer functions: A roadmap for future development, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17595, https://doi.org/10.5194/egusphere-egu23-17595, 2023.

08:45–08:55
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EGU23-9786
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On-site presentation
Yijian Zeng, Fakhereh Alidoost, Bart Schilperoort, Yang Liu, Meiert Willem Grootes, Yunfei Wang, Zengjing Song, Danyang Yu, Enting Tang, Qianqian Han, Christiaan van der Tol, Raúl Zurita-Milla, Michael Ying Yang, Serkan Girgin, Yifat Dzigan, and Zhongbo Su

Climate projections strongly suggest that the 2022 sweltering summer may be a harbinger of the future European climate. Climate extremes (e.g., droughts and heatwaves) jeopardize terrestrial ecosystem carbon sequestration. The construction of an open digital twin of the soil-plant system helps to monitor and predict the impact of extreme events on ecosystem functioning and could be used to recommend measures and policies to increase the resilience of ecosystems to climate-related challenges. A digital twin refers to a highly interconnected workflow, with a data assimilation framework at its core to combine observations and process-based models, meanwhile accompanied by an interactive and configurable platform that allows users to create and evaluate user-specific scenarios for scientific investigation and decision support. Creating an open digital twin means creating a digital twin following Open Science and FAIR principles, both for data and research software. In this contribution, the STEMMUS-SCOPE model was used as an example to develop an open digital twin of the soil-plant system. We suggest our recently developed open digital twin infrastructure could serve as the backbone for an interoperable framework to facilitate the digitalization of other Earth subsystems (e.g., by simply replacing the soil-plant model). In addition, we show how software not designed initially as open can be adopted to create an open digital twin using containers - standardized computational environments that can be shared, reused and that foster reproducibility.

How to cite: Zeng, Y., Alidoost, F., Schilperoort, B., Liu, Y., Willem Grootes, M., Wang, Y., Song, Z., Yu, D., Tang, E., Han, Q., van der Tol, C., Zurita-Milla, R., Yang, M. Y., Girgin, S., Dzigan, Y., and Su, Z.: Towards an Open Digital Twin of Soil-Plant System Following Open Science, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9786, https://doi.org/10.5194/egusphere-egu23-9786, 2023.

08:55–09:05
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EGU23-4789
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On-site presentation
Tamir Kamai and Shmuel Assouline

Evaporation is a significant part of the water cycle and the main process for water vapor exchange between Earth's surface and atmosphere. Evaporation from bare soil consists of two main stages: stage 1, with a relatively high and often steady evaporation rate that is controlled mainly by atmospheric conditions, and stage 2, with lower and exponentially decreasing evaporation rates that are limited by the diffusive nature of the vapor flow and the hydraulic properties of the drying medium. In dry or drought conditions that are characterized with long dry spells, stage 1 is short and during stage 2 water is depleted from the top near-surface soil, forming a dry soil layer (DSL), where water flows in vapor phase only. Measuring bare soil evaporation over larger areas is challenging due to the natural heterogeneity. These measurements become even more challenging under dry conditions, due to the equipment needed for capturing low fluxes under extremely high liquid water potentials and equivalent vapor pressures. Therefore, predictive tools are essential for estimation of soil evaporation. To date, modeling of this transient evaporation process is limited, mainly because it either requires sophisticated numerical models that account for its complexities or relies on analytical solutions that are too simplistic to capture its dynamics.
We present an analytical model that accounts for the main mechanisms of the evaporation process, but is relatively simple in its construction. The governing mechanisms during this dynamic process are captured by accounting for the hydraulic properties of the drying medium, the characteristic features of the medium that control water flow, the atmospheric forcing, and the partitioning between the liquid and vapor phases of the water within the drying profile. We validate this simplified approach using data from a numerical model and from evaporation experiments in different soil types, under various ambient conditions. In addition to depicting evaporation rates and the cumulative loss of water over time, we demonstrate the effect of soil hydraulic properties and their heterogeneity on the evaporation process. Additionally, we show how the model predicts the spatiotemporal partitioning between water (liquid and vapor) phases, with specific attention to the DSL that develops during longer periods of evaporation, with the corresponding downward migration of the evaporative front.

How to cite: Kamai, T. and Assouline, S.: Modelliing evaporation from soil profiles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4789, https://doi.org/10.5194/egusphere-egu23-4789, 2023.

09:05–09:15
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EGU23-12860
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On-site presentation
Andreas Güntner, Marvin Reich, Daniel Rasche, Theresa Blume, Stephan Schröder, Erik Brachmann, André Gebauer, and Hartmut Wziontek

Terrestrial gravimetry allows for integrative measurements of mass changes associated with water storage variations in all storage compartments above and below the Earth surface. Superconducting gravimeters (SGs) currently are the most precise instruments for continuous monitoring of gravity change. Their footprint typically covers a radius of about 1 km around the instrument, with most of the signal originating from within the first 100 meters. We installed a SG (iGrav033) in a mixed pine-beech-oak forest in the TERENO observatory in the lowlands of north-eastern Germany. It is housed in a small field enclosure with less than 1 m2 base area, on top of a stable concrete pillar. Complementary hydro-meteorological monitoring data are available at the site, including a weather station, a groundwater monitoring well, clusters of soil moisture sensors along deep soil profiles, interception measurements and near-surface soil moisture from Cosmic Ray Neutron Sensing. For quantification and correction of the long-term instrumental SG drift, repeated measurements with an FG5 absolute gravimeter were carried out. The gravity residual time series (gravity measurements reduced to the local hydrological effect) covers a sequence of years with below average precipitation, from 2018 to 2022. We show the gravity-based water storage variations in the forested landscape throughout this period, indicating that storage depletion during summer in most years is not fully recovered by the subsequent wetter winter periods. The amplitudes of gravity-based water storage variations tend to exceed those observed by soil moisture sensors in the top meters of the soil and of groundwater. This indicates the value of terrestrial gravimetry in revealing dynamics of the deeper unsaturated zone water storage.

How to cite: Güntner, A., Reich, M., Rasche, D., Blume, T., Schröder, S., Brachmann, E., Gebauer, A., and Wziontek, H.: Water storage variations in a forest during a sequence of dry years: integrative monitoring with a superconducting gravimeter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12860, https://doi.org/10.5194/egusphere-egu23-12860, 2023.

09:15–09:25
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EGU23-4390
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ECS
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On-site presentation
Sonia Akter, Johan Alexander Huisman, and Heye Reemt Bogena

Root-zone soil moisture (RZSM) information is valuable in a wide range of applications, including weather forecasting, hydrological and land surface modeling, and agricultural production. However, there is still a lack of sensing information that adequately represents RZSM, especially with regard to longer periods and larger spatial scales. For example, active and passive microwave remote sensing observations for soil moisture are limited to the topsoil and can be influenced by land cover type. One option for RZSM observation is terrestrial gamma radiation as it is inversely related with soil moisture. Hence, the near-real-time data of more than 4600 gamma radiation monitoring stations archived by the EUropean Radiological Data Exchange Platform (EURDEP) may be a potential source to develop a RZSM product for Europe without extra investments in sensors. The aim of this study was to investigate to what extent the EURDEP data can be used for RZSM estimation. For this, two gamma radiation monitoring stations were equipped with in-situ soil water content sensors to measure reference RZSM. The terrestrial component of gamma radiation was extracted after eliminating the contribution of secondary cosmic radiation. For this, it was assumed that the long-term contribution of secondary cosmic radiation is constant and that the variations are caused by changes in atmospheric pressure and incoming neutrons. In addition, precipitation effects creating a sudden increase in gamma radiation due to atmospheric washout of radon progenies to the ground were eliminated by excluding time periods with precipitation. Finally, multi-year terrestrial gamma radiation measurements were used to estimate weekly RZSM and the results were compared with the reference measurements. It was found that the seasonal variation of RZSM can be reasonably well predicted with an RMSE of 7 – 9 vol.% from gamma radiation measurements. However, the radiation-based RZSM estimates fluctuated with a much greater amplitude compared to the reference data, especially during the winter and spring season. This may be related to unknown or neglected additional sources that affect the gamma radiation signal and this needs to be further investigated. Although the accuracy of radiation-based RZSM estimates is not as good as many other in-situ sensors, this technique is still competitive with satellite-based remote sensing technique to estimate RZSM on the continental scale.

How to cite: Akter, S., Huisman, J. A., and Bogena, H. R.: Estimating root-zone soil moisture from gamma radiation monitoring data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4390, https://doi.org/10.5194/egusphere-egu23-4390, 2023.

09:25–09:35
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EGU23-12430
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ECS
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On-site presentation
Melissa Ruiz-Vásquez, Sungmin Oh, Alexander Brenning, Gianpaolo Balsamo, Souhail Boussetta, Gabriele Arduini, Markus Reichstein, and René Orth

Vegetation plays a fundamental role in modulating the exchange of water, energy, and carbon fluxes between the land and the atmosphere. These exchanges are modelled with Land Surface Models (LSMs) which are part of numerical weather prediction systems to support the performance of weather forecasts. However, most current LSMs only utilise observed vegetation information in the form of mean seasonal cycles. The potential benefits of additionally including information about shorter-term vegetation anomalies and inter-annual variability are understudied.

In this study, we update vegetation information in the HTESSEL (Hydrology Tiled ECMWF Scheme for Surface Exchanges over Land) model and investigate the resulting effects on the performance of simulated shallow and deep soil moisture as well as latent heat flux. The updated information includes an interactive observation-based leaf area index from Sentinel-3 and THEA GEOV2, and a land use/land cover map from ESA-CCI. The resulting simulations of soil moisture and latent heat flux are validated against global gridded observation-based datasets.

Results show that the updated land surface information deteriorates the overall model performance for both latent heat flux and soil moisture in most regions across the globe. In a second step, we re-calibrate soil and vegetation-related parameters at each grid cell in order to adjust them to the new vegetation information. This leads to improved model performance and illustrates the benefits of updated vegetation information. Morover, we attribute the spatial variations of parameter perturbations resulting from the re-calibration to multiple land surface and climate characteristics. This highlights potential venues in model development to take static ecological and hydroclimatological information into greater consideration.

Furthermore we compare the performances of local model calibration - performed for each grid cell individually - and global model calibration considering a single parameter set for all grid cells globally. We analyse the agreement of parameter calibrations obtained for shallow and deep soil moisture as well as latent heat flux.

In summary, our results highlight that Earth-observation products of vegetation dynamics and land cover changes can improve land surface model performances, which in turn can contribute to more accurate weather forecasts.

How to cite: Ruiz-Vásquez, M., Oh, S., Brenning, A., Balsamo, G., Boussetta, S., Arduini, G., Reichstein, M., and Orth, R.: Updating vegetation information in a land surface model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12430, https://doi.org/10.5194/egusphere-egu23-12430, 2023.

09:35–09:45
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EGU23-3368
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On-site presentation
Gerrit H. de Rooij

The most important parameterizations of the soil water retention curve do not perform very well in either the wet or the dry end. Rossi and Nimmo (WRR 1994) therefore gave the Brooks-Corey (1966) power-law model of the soil water retention curve a non-asymptotic dry range. Ippisch et al. (Adv. Water Resour., 2006) added an air-entry value to the sigmoidal retention model of van Genuchten (SSSAJ 1980). The models of Rossi and Nimmo and Ippisch et al. were Adapted by de Rooij (HESS 2021) to arrive at a sigmoidal, non-asymptotic soil water retention curve with an air-entry value, dubbed RIA. In RIA, the matric potential at oven-dryness, hd, appeared as a derived parameter.

Bittelli and Flury (SSSAJ 2009) showed that dry-range soil water retention data points often are unreliable. In order to make RIA robust when this is the case, this presentation explains how hd was made a fitting parameter that can be fixed if needed. This modification was complicated by the peculiar behavior of shape parameter α that made adequate parameter fitting impossible. The presentation elucidates this behavior and explains how this problem was solved by a reformulated model (de Rooij, HESS 2022). It then shows how earlier fits (when the problem had not yet been discovered) corroborate the reformulated model.

The work also offers support for a theoretical value for hd proposed by Schneider and Goss (Geoderma 2012), which is very helpful if dry-range data are lacking or of poor quality. The mathematical structure of RIA is such that, for α → ∞, Rossi and Nimmo’s model arises as a special case of RIA, and, by implication, Brooks-Corey as a special case of Ippisch et al.

A public-domain code to fit the parameters using shuffled complex evolution (SCE) is available on Zenodo (de Rooij, 2022). It has features that help the user identify issues with local minima and overparameterization, and provides more information than most codes to offer better insight into the fitting process for those familiar with the SCE algorithm. These features may be useful for other parameter identification problems, so they will be discussed as well.

How to cite: de Rooij, G. H.: A new sigmoidal but non-asymptotic soil water retention curve for the entire soil water content range brings together the van Genuchten and Brooks-Corey models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3368, https://doi.org/10.5194/egusphere-egu23-3368, 2023.

09:45–10:15
Coffee break
Chairpersons: Stefano Barontini, Marco Peli, Martina Siena
10:45–10:50
10:50–11:00
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EGU23-9384
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On-site presentation
Valentin Couvreur, Poonam Mehra, Bipin K. Pandey, Xavier Draye, and Malcolm J. Bennett and the co-authors

Plant roots exhibit plasticity in their branching patterns to forage efficiently for heterogeneously distributed resources, such as soil water. The xerobranching response represses lateral root formation when roots lose contact with water (e.g. in “air gaps”), and provides an experimental model to study root adaptive responses to transient water stress.

To discover the mechanistic basis of xerobranching, soil- and agar-based xerobranching bioassays were developed. As levels of the abiotic stress signal abscisic acid (ABA) increase in root tips during transient water stress, we observed that tomato, maize and Arabidopsis mutants deficient in ABA are disrupted in xerobranching response. Using novel ABA biosensors and mutants, we showed that when reaching an air gap, it takes about half a day for ABA originating from phloem tissues to radially travel through the unloading zone and accumulate in epidermal tissues.

When root tips lose contact with water, could the direction of water flow across root tissues change, and trigger the outwards accumulation of ABA, acting as a “hydrosignal” ? Our 3-dimensional root micro-hydrological model of solute advection-diffusion “MECHA” supports the following hypotheses :

  • Such a reversal of radial water flow direction may happen in the root elongation zone, as cell elongation may not be fed by water absorbed at the root surface anymore, and therefore water for cell elongation (e.g. in the epidermis) entirely relies on phloem as a water source.
  • If water soluble hormones such as ABA “ride” on water fluxes through plasmodesmata and along cell walls, it would take them about 8 hours to accumulate to levels comparable to concentrations observed in phloem cells. This timing is compatible with our experimental observations.

From there on, our Arabidopsis mutants reveal that ABA uses plasmodesmatal closure to lock up the symplastic radial pathway that is necessary for auxin to initiate lateral root branching.

In conclusion, our study reveals how roots might adapt their branching pattern to heterogeneous soil water conditions by linking changes in hydraulic flux with dynamic hormone redistribution.

This work includes material recently published in Science, under the following link: https://doi.org/10.1126/science.add3771

How to cite: Couvreur, V., Mehra, P., Pandey, B. K., Draye, X., and Bennett, M. J. and the co-authors: Hydrosignalling : How air gaps in soils alter the distribution of root water and hormones fluxes, thereby blocking root lateral branching, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9384, https://doi.org/10.5194/egusphere-egu23-9384, 2023.

11:00–11:10
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EGU23-10495
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On-site presentation
Markus Berli and Rose Shillito

Infiltration is an important hydrological process impacting ecology, forestry, agronomy, civil- and environmental engineering. Most infiltration models assume soils to be “wettable”, i.e., water in the soil forming an effective contact angle with the soil matrix that is close to zero. For a range of applications, e.g., infiltration into organic-rich soils or soils that turned water repellent due to fire, the “wettability assumption” no longer holds. Hence, the need for an infiltration model that can take soil water repellency into account. This study proposes a process-based approach for modeling infiltration into water repellent soil using the concepts of effective contact angle and sorptivity. The approach was developed using the Green-Ampt infiltration model but can be easily adapted for other process-based infiltration models such as Philip or Smith-Parlange. The infiltration model demonstrates the considerable impact of soil water repellency on infiltration, also for subcritically-water repellent soils, i.e., soils with effective contact angles <90°. It illustrates the non-linear relationship between infiltration rate and effective contact angle with effective contact angles >70° having a much larger impact on infiltration rate than effective contact angles <70°. The model also indicates that due to gravity, infiltration could occur into super-critically water repellent soil (i.e., soil with effective contact angles ≥90°), even with zero hydraulic head at the soil surface. Infiltration at zero hydraulic head, however, likely ceases at effective contact angles between 91° and 101°, depending on the amount of cumulative infiltration. All infiltration simulations showed decreasing infiltration rates with increasing soil water repellency expressed as effective contact angle or sorptivity at any level of cumulative infiltration. Finally, the water repellency effects on infiltration rates for short-duration, high intensity storms—a critical situation commonly associated with wildfire and flooding—were illustrated.

How to cite: Berli, M. and Shillito, R.: Modeling infiltration into water repellent soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10495, https://doi.org/10.5194/egusphere-egu23-10495, 2023.

11:10–11:20
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EGU23-12011
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ECS
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Virtual presentation
Shawkat Basel Mostafa Hassan, Giovanna Dragonetti, Alessandro Comegna, Asma Sengouga, Nicola Lamaddalena, and Antonio Coppola

A new pedotransfer function (PTF) was developed based on the Arya and Paris (AP) approach to obtain Water Retention (WRC) and Hydraulic Conductivity (HCC) curves. The AP approach obtains the unimodal WRC from the Particle-Size Distribution (PSD). The proposed PTF is an extension of AP approach by incorporating the Aggregate-Size Distribution (ASD) to include the inter-aggregate pores (macropores) retention, and thus obtain the bimodal WRC. A bimodal porosity model was developed to specify the ratios of the matrix and the macropores in the overall soil porosity. Kozeny-Carmen equation was utilized to obtain the saturated hydraulic conductivity, K0, from the bimodal WRC behaviour near saturation. Then, Mualem model was applied to obtain the full HCC. To calibrate the proposed PTF, soil physical and hydraulic properties were measured from a 140-ha irrigation sector in “Sinistra Ofanto” irrigation system in Apulia Region, South Italy. Hydraulic properties came from infiltration experiments. Infiltration data were fitted using bimodal and unimodal hydraulic properties by an inverse solution of Richards Equation. The scaling parameter of the proposed PTF, αAP, was calibrated using the measured bimodal hydraulic properties. A similar calibration was carried out for the sake of comparison, in which the αAP of the classical unimodal AP was calibrated using the unimodal hydraulic properties. The proposed bimodal AP (bimAP) PTF significantly improves the predictions of the mean WRC parameters, K0 and the entire HCC, compared to the classical unimodal AP (unimAP) PTF. In addition, compared to unimAP, bimAP allows to reproduce the statistics of the hydraulic parameters (e.g., the variance) similar to those obtained from field measurements. Finally, Multiple Linear Regression (MLR) was applied to study the sensitivity of bimodal αAP to the soil textural and structural properties and the results confirmed the significant predictive effects of soil structure.

How to cite: Hassan, S. B. M., Dragonetti, G., Comegna, A., Sengouga, A., Lamaddalena, N., and Coppola, A.: A bimodal extension of the ARYA&PARIS approach for predicting hydraulic properties of structured soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12011, https://doi.org/10.5194/egusphere-egu23-12011, 2023.

11:20–11:30
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EGU23-17401
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ECS
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On-site presentation
Shahla Asgharinia, Micaela Lembo, Vanessa Eramo, Roberto Forniti, Francesco Renzi, Riccardo Valentini, and Rinaldo Botondi

Ag-IoT systems enable a data pipeline for modern agricultural production. Using Ag-IoT technologies, growers can make better management decisions by leveraging the real-time field data while researchers could utilize these data to answer key scientific questions. Here, we designed a flexible microprocessor-based platform, called TreeTalker, to monitor in real-time plant sap flow rate via thermal approaches. TreeTalker has an onboard spectrometer to collect data in near infrared and visible areas using 12 bands from 450 to 860 nm. Moreover, TreeTalker collects microclimate data (air temperature and air relative humidity) as well as soil moisture and temperature measurement. Sap flow and soil moisture measurements are the main tools to understand the plant water demand for precision irrigation and water-energy efficiency. In this study, 9 TreeTalker units are mounted on Soreli Kiwifruit trees in the Lazio region, Italy. The site is divided into three clusters with different irrigation regimes, 100, 80 and 60 %, respectively. The first objective of this study was to apply new algorithms for sap flow measurement considering the heating and cooling phases of the heat flow curve at the same time and secondly, a compare of phenological and ecohydrological trends of trees under full and deficit irrigation systems. Data captured was used to analyze the correlation between fruit quality, productivity, health, and fertility of trees with ecophysiological parameters under different irrigation systems. The result of continuous monitoring for one growing season in 2022 revealed that sap flow function based on cooling phase data has higher accuracy than heating phase due to independency to the zero-flux condition as well as semi-theoretical flow index. Given sap flow results, plants with the full irrigation system have ∼ 1.3 to 3 times greater sap flow rate than plants with deficit irrigation regimes. Kiwi peak water demand occurred in July coinciding with max VPD confirming maximum sap flow rates between each irrigation regime. A variation between the 80% and 60% irrigation regimes, ∼ 4 to 15 %, is linked to slight differences in sap flow rates and is most prominent in the early part of the growing season. Considering fruit quality data, kiwifruit trees with full irrigation showed lower acidity, and higher Vitamin C concentration while sugar concentrations were noticeably lower. Our results suggest that the 80% irrigation schedule achieves the optimum water energy efficiency as well as reaching optimum fruit quality conditions. This finding requires validation via continued monitoring over successive seasons and irrigation regimes. The revolution in the Internet of trees offers a promising new big data solution for assessing optimal conditions for fruit tree agricultural production considering future and potential water scarcity scenarios.

How to cite: Asgharinia, S., Lembo, M., Eramo, V., Forniti, R., Renzi, F., Valentini, R., and Botondi, R.: Ag-IoT application for Vital Monitoring of Plant Ecophysiological Data and Soil Parameters, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17401, https://doi.org/10.5194/egusphere-egu23-17401, 2023.

11:30–11:40
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EGU23-12613
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ECS
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On-site presentation
Fabian Wankmüller, Louis Delval, Andrea Cecere, Peter Lehmann, Mathieu Javaux, and Andrea Carminati

At a critical soil water content (θcrit), terrestrial ecosystem fluxes at the soil-vegetation-atmosphere interface transition from energy into water limitation. Understanding and predicting soil, plant and atmospheric mechanisms that control θcrit are central to interpreting and predicting impacts of drought on ecosystems, including the associated feedbacks to carbon and hydrological cycle. Thanks to the existing monitoring networks, θcrit can now be estimated globally across soils, biomes and climates. However, the mechanisms and key parameters that explain θcrit as a result of soil-, plant-, and climate-interaction remain elusive. Here, we show that the soil hydraulic conductivity function determines mean and variability of θcrit. The underlying concept to calculate θcrit assumes that soil moisture limitation of transpiration is triggered by a loss in soil hydraulic conductivity around the roots. Taking soil-specific hydraulic properties into account, our soil-plant hydraulic model predicts the observed mean and variance of θcrit as a function of soil textural classes. In coarse textured soils, θcrit is small due to the lower absolute soil hydraulic conductivity and its steeper decline with soil drying compared to fine textured soils. The increasing variability of θcrit in fine-textured soils is explained by (i) the wide range of hydraulic conductivity values for similar soil textures as a result of soil structure formation and (ii) by the higher sensitivity to plant traits and climate for soils with less steep hydraulic conductivity curves (i.e., loamy soils). The corresponding critical soil matric potential (hcrit) is also soil texture specific, and it covers a broad range of values, from values close to field capacity in sandy soils (hcrit ca. -100 hPa) to values close to the wilting point in clay soils (hcrit ca. – 1 MPa). The model implies that climate change has a smaller effect on θcrit in sandy soils, suggesting that soil texture modulates climate effects on water use and photosynthesis globally. Overall, our results prove the prominent role of soil hydraulic conductivity for water limitation of ecosystem fluxes and for plants’ potential to adjust to water limitations subject to alterations due to climate change.

How to cite: Wankmüller, F., Delval, L., Cecere, A., Lehmann, P., Javaux, M., and Carminati, A.: Soil Hydraulic Conductivity Controls Soil Moisture Limitation of Transpiration Globally, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12613, https://doi.org/10.5194/egusphere-egu23-12613, 2023.

11:40–11:50
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EGU23-15294
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On-site presentation
Peter Lehmann and Andrea Carminati

The partitioning between soil evaporation and transpiration from plants is an important process of water and carbon cycles and surface energy balance. Its quantification is prone to errors because of the complexity of flow geometry, which is affected by the variation of root length density over depth and time and the dynamics of soil hydraulic properties in the rhizosphere. Root water uptake and concurrent evaporation depend on the forces (capillarity, gravity, and viscous losses) controlling water flow and propagation of the drying front. We simulate the water flow from the soil to the atmosphere using invasion percolation models, draining elements as a function of the retaining forces depending on the lengths of the potential flow paths. The partitioning between evaporation and transpiration is simulated for different pore size distributions, root length densities, and vegetation covers controlling the transpiring area. Starting with a three dimensional percolation model (to reproduce the connectivity of the liquid phase) at the column scale consisting of elements in the submillimeter range, we deduce one-dimensional partitioning rules for wet and dry soils. As an outlook, we discuss how these rules can be (i) implemented in large scale models and (ii) tested by measuring vapor fluxes above and below canopy.

How to cite: Lehmann, P. and Carminati, A.: Modeling the partitioning of evapotranspiration using invasion percolation theory, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15294, https://doi.org/10.5194/egusphere-egu23-15294, 2023.

11:50–12:00
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EGU23-4336
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ECS
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Virtual presentation
Yi Luo, Jiaming Zhang, Zhi Zhou, Juan Pablo Aguilar López, Roberto Greco, and Thom Bogaard

Preferential flow induced by desiccation cracks (PF-DC) has been proven to be an important hydrological effect that could cause various geotechnical engineering and ecological environment problems. Investigation on the PF-DC remains a great challenge due to the soil shrinking-swelling behavior. This work presents an experimental and numerical study of the PF-DC considering the dynamic changes of DC. A soil column test was conducted under wetting-drying cycles to investigate the dynamic changes of DC and their hydrological response. The ratio between the crack area and soil matrix area (crack ratio), crack aperture and depth were measured. The soil water content, matrix suction and water drainage were monitored. A new dynamic dual-permeability preferential flow model (DPMDy) was developed, which includes physically-consistent functions in describing the variation of both porosity and hydraulic conductivity in crack and matrix domains. Its performance was compared to the single-domain model (SDM) and rigid dual-permeability model (DPM) with fixed crack ratio and hydraulic conductivity. The experimental results showed that the maximum crack ratio and aperture decreased when the evaporation intensity was excessively raised. The self-closure phenomenon of cracks and increased surficial water content were observed during low evaporation periods. The simulation results showed that the matrix evaporation modeled by the DPMDy is lower than that of the SDM and DPM, but its crack evaporation is the highest. Compared to the DPM, the DPMDy simulated a faster pressure head building-up process in the crack domain and higher water exchange rates from the crack to the matrix domain during rainfall. Using a fixed crack ratio in the DPM, whether it is the maximum or the average value from the experiment data, will overestimate the infiltration fluxes of PF-DC but underestimate its contribution to the matrix domain. In conclusion, the DPMDy better described the underlying physics involving crack evolution and hydrological response with respect to the SDM and DPM. Further improvement of the DPMDy should focus on the hysteresis effect of the SWRC curve and soil deformation during wetting-drying cycles.

How to cite: Luo, Y., Zhang, J., Zhou, Z., Pablo Aguilar López, J., Greco, R., and Bogaard, T.: Effects of dynamic changes of desiccation cracks on preferential flow: Experimental investigation and numerical modeling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4336, https://doi.org/10.5194/egusphere-egu23-4336, 2023.

12:00–12:30

Posters on site: Wed, 26 Apr, 16:15–18:00 | Hall A

Chairpersons: Stefano Barontini, Marco Peli, Sara Bonetti
A.188
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EGU23-82
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ECS
Leila ElGhoul, Fatma Wassar, Fathia El Mokh, and Kamel Nagaz

Water scarcity is a limiting factor for agricultural development. Accordingly, the improvement of its efficiency is indispensable through the application of adequate irrigation strategies including deficit irrigation. In this context this work was undertaken. A field experiment have been carried out in Beni Khdache, south of Tunisia on grapevines to evaluate the agronomic responses, in terms of crop development, yield, yield quality and water productivity, under different water regimes. The first treatment (T100) consisted in delivering to the crop 100% of the ETc. The other two treatments (T75 and T50) consisted in delivering only 75 and 50% of the total real needs of the crop respectively. The fourth treatment (T0) was irrigated according to the farmer's recommendations. The results show a significant effect of the deficit irrigation on the vegetative growth of the grapevines in terms of berry weight. This difference had later a significant impact on the final yield. The highest yield (14t/ha) was found with full irrigation (T100). The farmer's method led to a significant drop in yield (40%) compared to the full irrigation treatment. Trees under water deficit (T75, T50) responded with an accumulation of sugars (17.3 °Brix and 16.8° Brix respectively) and a slight decrease in fruit acidity (3.9 and 3.8 respectively) compared to the T100 treatment (15°Brix,4) .  The difference in irrigation water productivity of the grapevines obtained with the deficit irrigation treatments (T75, T50) is not significant compared to that of T100.  The low water productivity was observed for the T0 and T75 treatments (1.9kg/m3 and 2.4 kg/ m3 respectively), while the highest values were obtained with the T50 and T100 treatments (2.8 kg/m3 and 2.6 kg/m3). These results indicate that full irrigation (T100) seems to be an adequate irrigation strategy for grapevine production under Tunisian arid conditions. Under water scarcity conditions, deficit irrigation with a 25% reduction in inputs (T75) is recommended for grapevine management. The T75 deficit irrigation treatment allows to save large amounts of irrigation water (25%) and to improve water productivity but accepting a certain yield drop.

Keywords: Full irrigation, deficit irrigation, grapevine, yield, water productivity, arid environment, farmer's practices

How to cite: ElGhoul, L., Wassar, F., El Mokh, F., and Nagaz, K.: Grapevine agronomic responses to different water regimes south of Tunisia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-82, https://doi.org/10.5194/egusphere-egu23-82, 2023.

A.189
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EGU23-1237
Vladimir Tyurin, Reza Taherdangkoo, and Christoph Butscher

Soil-water retention is fundamental to understand hydro-mechanical characteristics of unsaturated clayey soils. The soil-water retention curve (SWRC) depends on internal (e.g. mineralogical composition, and chemo-physical properties of soils) and external (e.g. stress states and temperature) factors. The SWRC is usually determined through laboratory testing, which is costly and time consuming. In this study, we compiled an experimental dataset containing water retention data of artificial and natural clayey soils to develop a deep neural network (DNN) model trained with genetic algorithm (GA) to estimate SWRC over a wide suction range. The relevant soil properties including dry density, liquid limit, plastic limit, plasticity index, initial water content, void ratio, and suction are the input variables of the DNN-GA model, while the gravimetric water content is the output variable. The analysis of modeling errors and the comparison of gravimetric water content predicted values with experimental values showed the high efficiency of the model being developed. The DNN-GA model can be used as an accurate alternative to classical soil mechanic correlations.

How to cite: Tyurin, V., Taherdangkoo, R., and Butscher, C.: A deep neural network model to estimate water retention of compacted clayey soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1237, https://doi.org/10.5194/egusphere-egu23-1237, 2023.

A.190
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EGU23-1053
Jay Jabro and Bart Stevens

Tillage alters soil structure and pore size distribution, consequently affecting the shape of the soil-water retention curve (SWRC) and related hydraulic parameters in the top layer of soil. This work compares the effect of no-tillage (NT) and conventional tillage (CT) practices on SWRCs at 0-15 and 15-30 cm soil depths based on soil samples collected in 2014, 2015, 2016, and 2017. Undisturbed soil cores were extracted using stainless steel cylinders (8 cm in diameter and 5 cm in height) from 0-15 cm and 15-30 cm depths in planted corn rows. Soil core sampling was replicated five times in a randomized block design. Soil cores were saturated prior to measurement by the capillarity method and SWRC were measured using the evaporative method. Measured soil-water retention curve data were modeled for no-tilled and tilled soils using the van Genuchten (vG) equation for each depth. Results indicated that differences existed in SWRC properties and estimated parameters of vG equation between the two tillage practices. Averaged across 4 years and two depths, the SWRC parameters α, n, and θs were significantly greater under CT than under NT, however, θr was not affected by tillage. The higher α, n, and θs values in CT were likely associated with greater soil loosening and disturbance induced by CT operations, thereby forming greater macroporosity and pore volume. Regardless of the tillage method, SWRCs enable growers to select farming and irrigation management practices that improve water use efficiency, sustain crop productivity and maintain environmental quality.

How to cite: Jabro, J. and Stevens, B.: Soil-water characteristic curves and their estimated parameters as affected by tillage intensity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1053, https://doi.org/10.5194/egusphere-egu23-1053, 2023.

A.191
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EGU23-2285
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ECS
Vahid Sobhi Gollo, Eva González, Jörg Elbracht, Peter Fröhle, and Nima Shokri

Soil salinization, referring to the excessive accumulation of soluble salts in soil to a degree that adversely influences vegetation and environmental health, is an unfolding challenge threatening soil health, vegetation and consequently food security with serious socio-economics implications (Hassani et al., 2020, 2021). High salinities in the root zone reduce water and nutrient uptake and result in soil infertility, freshwater contamination at the surface and the loss of biodiversity.

Here, we concentrate on soil salinization in coastal areas due to saltwater intrusion and the groundwater salinization, partly influenced by climate change.  In low-lying coastal regions where, saline groundwater levels are shallow, saltwater intrusion poses risks to vegetation and soil health since the soluble salt could be transported toward the surface. This causes soil salinization depending on the competition between upward capillary forces and the limiting downward gravity and viscous forces. Several parameters influence such a competition including soil texture and heterogeneity. We developed a quantitative framework, using software package FEFLOW, to delineate the regional impact of soil textures and arrangements on salt transport toward the surface in low-lying coastal regions. The model includes a wide range of hydrologic, soil and climate related factors such as hydraulic heads, soil properties, and groundwater recharge. We evaluated the performance of the developed model using field data measured in the “Alte Land” located in north Germany near the Elbe estuary - an agriculturally significant low-lying region threatened by increasing soil surface salinity.

The evaluation of the model against field-data was followed by conducting the simulation under several hypothetical scenarios differing in soil textures, layering and arrangements to investigate how these parameters would influence soil surface salinity driven by the saltwater intrusion in coastal areas.  Our results highlight the prominent effects of different soil textures and arrangements on the regional surface soil salinity and the amount of salt deposited close to the surface. This agrees with the conclusions of laboratory experiments which were conducted in other studies at scales much smaller than the one investigated in our analysis (Shokri-Kuehni et al., 2020). Our results suggest that an effective soil remediation strategy for salinity treatment would require high resolution 3D mapping of soil properties which influences soil salinization. Our findings shed new light on the dominant parameters influencing surface soil salinity in coastal areas threatened by the saltwater intrusion as a result of the projected climate changes.

 

References

Hassani, A., Azapagic, A., Shokri, N. (2020). Predicting Long-term Dynamics of Soil Salinity and Sodicity on a Global Scale, Proc. Nat. Acad. Sci., 117 (52), 33017-33027.

Hassani, A., Azapagic, A., Shokri, N. (2021). Global Predictions of Primary Soil Salinization Under Changing Climate in the 21st Century, Nat. Commun., 12, 6663.

Shokri-Kuehni, S.M.S., Raaijmakers, B., Kurz, T., Or, D., Helmig, R., Shokri, N. (2020). Water Table Depth and Soil Salinization: From Pore-Scale Processes to Field-Scale Responses. Water Resour. Res., 56, e2019WR026707.

How to cite: Sobhi Gollo, V., González, E., Elbracht, J., Fröhle, P., and Shokri, N.: Impact of soil texture and heterogeneity on complex interactions between surface soil salinity and saltwater intrusion in coastal regions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2285, https://doi.org/10.5194/egusphere-egu23-2285, 2023.

A.192
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EGU23-2711
|
ECS
Anastasia Vogelbacher, Kaveh Madani, and Nima Shokri

Climate, climate variability, and climate change could influence groundwater. Shifts in precipitation patterns, recharge, or snowmelt are among the several climate-related variables with important impacts on groundwater. However, the climate-groundwater relationship is not one-way. Groundwater can also impact the climate itself via its influence on different processes and variables such as evaporation, soil moisture, and vegetation. Understanding the interactions and the feedback relationship between groundwater and climate is crucial for sustainable water resource management and resilient adaptation to climate change. Current understanding of how climate influences groundwater and the resulting feedback from groundwater and its impacts on climate is limited. This is of particular importance in the face of projected climatic changes. Here, we aim to develop a simple analytical framework to extend the projection capabilities required to characterize the climate-groundwater interactions depending on the soil characteristics serving as an intermediate domain between the groundwater and climate systems. Our proposed analytical framework can be used to identify potential regions with significant two-way (bidirectional) interactions between climate and groundwater using soil characteristics and soil water retention curves following the theoretical lines discussed in Shokri and Salvucci (2011) and Or and Lehmann (2019). Using this framework, we identify regions of expected hydraulic connections between groundwater and soil surface, depending on the competition between capillary forces and the limiting gravity and viscous forces, and the groundwater depth (GWD) in the city of Hamburg. We argue that in regions with bidirectional interactions, groundwater is potentially more vulnerable to climate change and variability. Moreover, our initial results suggest that regions with finer textured soils are more sensitive to changes in evaporation and air temperature in terms of hydraulic connections between groundwater and the soil surface, which can influence the groundwater-climate interactions. Our analysis provides the basis for further investigation of the feedback impacts of groundwater on several variables, such as soil moisture, ground cooling capacity, and vegetation patterns under different climate change scenarios.

 

References

Or, D., & Lehmann, P. (2019). Surface evaporative capacitance: How soil typeand rainfall characteristics affect global‐scale surface evaporation. Water Resources Research, 55, 519–539.https://doi.org/10.1029/2018WR024050.

Shokri, N., Salvucci, G. (2011). Evaporation from porous media in the presence of a water table. Vadose Zone J., 10, 1309-1318.

How to cite: Vogelbacher, A., Madani, K., and Shokri, N.: Modes of interaction and varying feedback between groundwater and climate depending on soil characteristics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2711, https://doi.org/10.5194/egusphere-egu23-2711, 2023.

A.193
|
EGU23-2753
Jakub Jeřábek and David Zumr

Accurate prediction of infiltration into the soil is essential for a variety of applications, including irrigation planning, flood prediction, and pollutants transport. In this study, we applied a two-dimensional model for simulating infiltration in heterogeneous soils, focusing on the effects of topsoil-subsoil interface morphology with the presence of wheel tracks. The model is based on the Richards equation and includes different soil hydraulic properties (SHP) for three soil materials: topsoil, subsoil and wheel track. To examine the effects of the topsoil-subsoil interface and wheel track compaction on infiltration, we conducted field experiments on a 16 m2 plot with simulated rain with constant precipitation intensity. We collected soil moisture and soil water pressure data at different depths and used these data to optimize the SHPs. The topography of the soil surface and the morphology of topsoil-subsoil interface were also recorded using photogrammetric methods. The results of the model simulations show that the topsoil-subsoil interface and wheel track compaction have significant effects on infiltration. The topsoil-subsoil interface acts as an infiltration barrier. The morphology of the interface causes a large heterogeneity in the water flow field and completely diminishes the effect of the slope on the water flow. The wheel track caused an infiltration excess overland flow while the topsoil outside the wheel track exhibited saturation excess overland flow. Subsoil in the wheel track remained unsaturated throughout the rainfall simulation period, affecting water redistribution after the rainfall ended. This study demonstrates that even the small-scale heterogeneity in the shallow part of the soil profile strongly influences the water flow field. The disturbed flow field can affect the distribution of water and nutrients in the root zone and potentially cause the activation of preferential pathways due to the spatial variability of saturation at the topsoil-subsoil interface. The work presented above was supported by an EU TuDi project no. 101000224 and by State Environmental Fund of the Czech Republic project no. 085320/2022.

How to cite: Jeřábek, J. and Zumr, D.: Two-Dimensional Modeling of Infiltration in Heterogeneous Soils: The Effects of Topsoil-Subsoil Interface and Wheel Track Compaction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2753, https://doi.org/10.5194/egusphere-egu23-2753, 2023.

A.194
|
EGU23-6975
|
ECS
Mohamad Abbas, Jacques Deparis, Arnaud Isch, and Céline Mallet

The hydrological characterization of the vadose zone remains a major challenge considering the spatiotemporal variability of its properties and the limitations associated with hydrological measurements techniques. Geophysical methods, in particular the DC-resistivity and ground penetrating radar, can provide large scale images of hydrogeological structures and a non-invasive assessment of the subsurface dynamic processes. However, these approaches rely on the accuracy of the petrophysical relationships connecting the geophysical parameters to hydrogeological ones, where the site-specific determination of the associated petrophysical parameters is considered crucial. The first objective of this study was to investigate the relationship between the water content, geological properties, and geophysical attributes at the vadose zone of a vulnerable limestone aquifer. The second objective aimed to obtain the Archie’s and Complex Refractive Index Model (CRIM) petrophysical parameters by using borehole electrical resistivity and cross-hole ground penetrating radar data. For this purpose, we adopted a grid search inversion algorithm where the field geophysical data were integrated with water content profiles simulated by using HYDRUS-1D. The vadose zone profile was divided into three layers, and the inversion was carried out for the petrophysical parameters in each of the model layers. The electrical resistivity and relative dielectric permittivity data showed a very good correspondence with the simulated and experimental water content distributions along the vadose zone profile. The petrophysical parameters estimated by the inversion showed values that fall in the ranges reported in the literature. Similar values have been observed in the different model layers, with slight differences that were attributed to the vertical heterogeneities associated with the alteration and fracturation features of the limestone vadose zone. This study showed a very good correlation between geophysical, hydrogeological and geological data, and highlighted the presence of heterogeneities that can have profound effects on the vadose zone water dynamics.

How to cite: Abbas, M., Deparis, J., Isch, A., and Mallet, C.: Hydrogeophysical characterization of a limestone vadose zone and determination of the Archie and CRIM petrophysical parameters by integrating geophysical and hydrogeological data in a grid search algorithm, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6975, https://doi.org/10.5194/egusphere-egu23-6975, 2023.

A.195
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EGU23-5461
|
ECS
|
Dimaghi Schwamback, Magnus Persson, Ronny Berndtsson, Luis Bertotto, Alex Kobayashi, and Edson Wendland

Automated soil moisture systems are commonly used in precision agriculture and environmental monitoring. Using low-cost sensors, the spatial extension can be maximized, but the accuracy might be reduced. In this paper, we address the trade-off between cost and accuracy comparing low-cost and commercial soil moisture sensors. The analysis is based on the capacitive sensor SKU:SEN0193 under lab and field conditions. The laboratory tests aimed at evaluating the response speed, best supply voltage, temperature dependency, calibration, and applicability for controlled infiltration column tests (one meter high). Laboratory tests indicated that the sensor is temperature and voltage-sensitive. The use of 5.5 V as supply voltage for the sensors drastically reduced the correlation between output and degree of soil saturation, thus we suggest the use of 3.3V. Soil temperature had a negligible impact on the sensor output: 0.27% of soil saturation degree per degree Celsius. For field implementation, a low-cost monitoring station was built using Arduino as a microcontroller and tested during three months. The sensors could represent daily and seasonal oscillation in soil moisture resulting from solar heating and precipitation. In addition to individual calibration, two simplified calibration techniques are proposed: universal calibration, based on all 63 sensors, and a single-point calibration using the sensor's response in dry soil. The monitored wetting front was compared to the one estimated by Hydrus model and had a high correlation. The low-cost sensor performance was later compared to commercial sensors based on five variables: (1) cost, (2) accuracy, (3) qualified labor demand, (4) sample volume, and (5) life expectancy. Commercial sensors promote soil moisture measurements with high accuracy at a high acquisition cost. On the other hand, low-cost sensors, such as the SKU:SEN0193, provide data with medium accuracy at a very low acquisition cost, enabling spatial monitoring through multiple-point measurements. Thus, the use of the SKU:SEN0193 sensor is suggested in projects with budget limitations with short duration where there is a medium requirement accuracy or when the spatial variability of soil water content is considerable. Despite the physical fragility of the hardware used (sensors and monitoring station) and the lower accuracy when compared to other commercial sensors, this work demonstrates through the case study of the SKU:SEN0193 sensor the possibility of using low-cost technologies for monitoring environmental variables.

How to cite: Schwamback, D., Persson, M., Berndtsson, R., Bertotto, L., Kobayashi, A., and Wendland, E.: Automated Low-Cost Soil Moisture Sensors: Trade-Off Between Cost and Accuracy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5461, https://doi.org/10.5194/egusphere-egu23-5461, 2023.

A.196
|
EGU23-5628
|
ECS
Filip Kiałka, Omar Flores, Kim Naudts, Sebastiaan Luyssaert, and Bertrand Guenet

Soil (de)compaction is widespread and has a large impact on soil constitutive relationships including hydraulic and gas-exchange properties. Surveys estimate that about a third of EU soils are severely degraded by compaction, and lab experiments show that the effect of compaction on soil hydraulic conductivity can be as large as the differences between textural classes. Nevertheless, the effect of (de)compaction on soil properties remains absent or only provisionally represented in present-day soil-crop, ecosystem, and land-surface models. That is despite the formulation of soil structure evolution models for key land management practices, biotic factors, and wet-dry or freeze-thaw cycles. The slow maturing and uptake of these models results from observational limitations and from difficulties with upscaling and with relating their outputs to soil properties of interest. Here we address the latter by extending established models of soil hydraulic properties to represent a dynamically evolving soil structure parametrized by a discrete pore-size distribution. The extension decomposes a given water retention curve into smooth algebraic segments corresponding to predefined pore size classes. The segments are then individually scaled to represent the changing pore volumes and summed to obtain the new retention and conductivity functions. We validate this approach using lab-based compaction experiments and demonstrate its use at site scale by leveraging the soil hydrology scheme of the ORCHIDEE land surface model. Finally, we discuss new applications that our approach enables, with a focus on representing the interaction between ecosystem engineers, soil structure, and soil water.

How to cite: Kiałka, F., Flores, O., Naudts, K., Luyssaert, S., and Guenet, B.: Representing the effect of (de)compaction on soil hydraulic properties using segmental constitutive laws, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5628, https://doi.org/10.5194/egusphere-egu23-5628, 2023.

A.197
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EGU23-6432
|
ECS
|
Veethahavya Kootanoor Sheshadrivasan and Jakub Langhammer

In continuation to the previously presented methodological approach to estimate vadose zone boundary fluxes titled “A novel conceptualization to estimate unsaturated zone mass-fluxes and integrate pre-existing surface- and ground- water models” at the EGU GA 2022, this study explores the performance of the outlined implementation and benchmarks the model.

 

To recap, the previous study presented a conceptual numerical scheme that aimed to adequately estimate the in- and out- fluxes of the Unsaturated Zone (UZ) with the primary aim of coupling existing groundwater (GW) and surface-water (SW) models. It was expected that such a numerical scheme would provide a viable alternative to solving the computationally expensive Richard’s model for cases where description of fluxes within the UZ and the spatial description of the soil moisture were not in the interest of the modeller. Examples of such cases would be efforts to model the hydro(geo)logical effects of various climate-scenarios, efforts to estimate GW recharge dynamically, and efforts to design integrated watershed management design structures and systems, among others.

 

The model numerical scheme has been implemented in Fortran for computational efficiency and a Python wrapper has been developed for the same for ease of use. The model itself is spatially agnostic and is solved for each model element discreetly, in the UZ. The global simulation period is split into local simulation periods between which the three models (GW, SW, and UZ) exchange information via a coupling scheme. At the beginning of each local simulation period, GW and SW states are read from the respective models (here MODFLOW 6 and Delft 3D - Flexible Mesh), the solution for the UZ is determined by the GWSWEX model given the precipitation and evapotranspiration rates, and the calculated discharges are then prescribed to the respective models. The internal time-step size for the local simulation period is dynamically determined based on the precipitation intensity. The coupling scheme harnesses the Basic Model Interface (developed by CSDMS) offered by both MODFLOW 6 and Delft 3D - Flexible Mesh to rapidly exchange information during the model run without having to restart the models. Support for multiple soil-type layers for the UZ is currently under development.

 

This study aims to assess and establish the capacity to simulate the fluxes of the UZ as desired by benchmarking it for the Tilted-V theoretical catchment setup and comparing its results to the physically based ParFlow model.

In addition to this, the study also aims to assess the reduction in computational resources achieved by employing a conceptual numerical scheme for solving the UZ fluxes.

 

It is expected that the findings of such a study shall point out any necessary improvements, bias-corrections, or considerations to be made in the model development before it may be applied to real-world applications.

The authors also hope that the study fosters discussions to unify the polarising modelling approaches as outlined in Markus Hrachowitz er al., 2017

How to cite: Kootanoor Sheshadrivasan, V. and Langhammer, J.: Performance assessment and Benchmarking of a conceptually coupled groundwater - surface-water model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6432, https://doi.org/10.5194/egusphere-egu23-6432, 2023.

A.198
|
EGU23-6853
Tobias Stacke, Philipp de Vrese, and Victor Brovkin
Earth System Models (ESMs) are the best available tools to project the coupled dynamics of the climate and biogeochemistry under future emission scenarios. However, the future trajectories simulated by individual ESMs vary substantially with most pronounced differences in the high northern latitudes. As recently demonstrated (de Vrese et al., 2022), a significant part of this uncertainty might result from the different approaches and parametrizations of surface and soil hydrology in the permafrost regions. However, this study did not account for sub-grid lateral fluxes.
To make a step forward, we further develop ICON-Land/JSBACH4, the land surface model (LSM) used within the ICON-ESM. Our recent efforts are focused on improving the simulation of Arctic hydrology by accounting for lateral water flows on small spatial scales, i.e. within the grid cells of the LSM. For this, we apply a tiling structure in which we define the spatial relation between parts of the grid cell in terms of water exchange. In this way, the model gets information about the source and sink tiles of surface runoff (based on topography) but also of lateral soil water exchange (based on proximity and soil moisture gradient).
This approach results in a redistribution of surface and soil water within the grid cells with drier upland and wetter lowland regions and the correspondent changes in evapotranspiration. Comparing coupled land-atmosphere simulations with different prescribed fractions of upland and lowland areas, we see strong impacts of the tiling structure. Setups with a larger lowland-to-upland ratios lead to higher cloud cover and by up to 2K lower summer surface temperature over larger parts of the boreal regions. This result emphasizes the importance of representing the complex processes of Arctic hydrology, but also the need for detailed information about Arctic land surface properties.

References:
de Vrese, P., Georgievski, G., Gonzalez Rouco, J. F., Notz, D., Stacke, T., Steinert, N. J., Wilkenskjeld, S., and Brovkin, V.: Representation of soil hydrology in permafrost regions may explain large part of inter-model spread in simulated Arctic and subarctic climate, The Cryosphere Discuss., https://doi.org/10.5194/tc-2022-150, in review, 2022.

How to cite: Stacke, T., de Vrese, P., and Brovkin, V.: Representation of Arctic hydrology in a global land surface model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6853, https://doi.org/10.5194/egusphere-egu23-6853, 2023.

A.199
|
EGU23-9183
|
ECS
Andre Dani Mawardhi and Seth Nathaniel Linga

Subak is a socio-agrarian-religious system of integrated terrace irrigation management on Bali island that involves indigenous peoples and religious aspects in distributing water sources evenly to rice fields. Regardless of its heritage value, Subak irrigation's performance in distributing water for rice is necessary in terms of water scarcity and food production issues. However, there is a limited number of works evaluating the Subak irrigation system's functioning, although it has been present for centuries. This study was conducted to assess the performance of Subak Ulumayu and Subak Sembung in 2018/2019. Several spatial datasets were processed using pySEBAL to generate biomass, evapotranspiration, and transpiration data. Results showed that rice consumed 968-1014 mm of water, which resulting 4.87-4.93 tons rice/ha in this season. Most subfields showed relatively good performance, i.e. Relatively Water Deficit <0.2, adequacy >80%, and equity CV<10%, although the Relatively Yield Deficit was high and efficiency was slightly low. According to those results, both Subak irrigation systems were working satisfactorily to supply water for rice fields among water users. However, there is a remained challenge to optimize rice productivity to contribute to national food security.

How to cite: Mawardhi, A. D. and Linga, S. N.: Technical Performance Assessment of the Subak Heritage Irrigation System in Bali, Indonesia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9183, https://doi.org/10.5194/egusphere-egu23-9183, 2023.

A.200
|
EGU23-9804
José Luis Gómez Flores, Mario Ramos Rodríguez, Mohammad Farzamian, Benito Salvatierra Bellido, Manuel López Rodríguez, and Karl Vanderlinden

Reclaimed saline marsh areas in SW Spain are characterized by a fragile balance in the rootzone between salt accumulation and leaching. Increasing climate variability and the introduction of new crops and irrigation methods can disrupt this balance, with undesirable environmental and economic consequences. In addition, the decreasing availability of irrigation water and the need to limit fertilizer use in areas vulnerable to nitrate contamination requires the implementation of more sustainable fertigation practices. A field experiment was set up in a commercial processing tomato field in the B-XII irrigation district (Lebrija, Seville) where four fertigation treatments (conventional and sustainable irrigation and fertilization) were compared in a random design with three replicates. Each elemental plot consisted of three tomato rows, each 250 m long and 1.5 m wide. Apparent electric conductivity (ECa) of each treatment was measured weekly using an electromagnetic induction sensor and multiespectral images were obtained on two dates using an UAV. ECa could be linked to the irrigation treatments and showed a strong within-treatment variability in accordance with the local soil characteristics and the depth of the underlying saline water table. The largest NDVI was observed for the sustainable irrigation and fertilization treatment, while the smallest NDVI corresponded to the sustainable fertilization and conventional irrigation treatment. Plants in the latter treatment presented chlorosis due to excessive accumulation of chloride and sodium in the leaves, as a result of root-zone salinization during the irrigation season, resulting in a strong decline in tomato yield (~60%) for this treatment. Overall, tomato yield showed a strong correlation with NDVI (R≈0.90). Our results suggest that more sustainable fertigation practices can be implemented in salinization-prone agricultural areas without increasing the risk of topsoil salinization or loss of crop productivity.

Acknowledgement

This work is funded by the Spanish State Agency for Research through grant PID2019-104136RR-C21/AEI/10.13039/501100011033, and by IFAPA/FEDER through grant AVA2019.018. Additionally, this work is also funded through PhD grant PRE2020-095133 by the Spanish State Agency for Research, and co-funded by the European Social Fund. 

How to cite: Gómez Flores, J. L., Ramos Rodríguez, M., Farzamian, M., Salvatierra Bellido, B., López Rodríguez, M., and Vanderlinden, K.: Soil and crop monitoring in a processing tomato fertigation experiment in a reclaimed saline marsh soil in SW Spain using proximal and remote sensing., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9804, https://doi.org/10.5194/egusphere-egu23-9804, 2023.

A.201
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EGU23-10919
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ECS
|
Julio Pachon, Daniel Hirmas, Hoori Ajami, Pamela Sullivan, Sharon Billings, Matthew Sena, Xi Zhang, Li Li, Karla Jarecke, Kamini Singha, Jesse Nippert, Alejandro Flores, and Xiaoyang Cao

Soil water retention is important for the establishment and productivity of ecosystems through its role in governing the flux, depth distribution, and availability of soil moisture. With increasing application of global and regional hydrologic and climate models, there is a concomitant need to accurately predict and map soil hydraulic properties to parameterize these models and simulate soil water dynamics across spatiotemporal scales. Soil water retention functions created to fulfill this need typically assume a unimodal pore-size distribution, despite the common observation that soil pore-size distributions are multimodal due to soil structure and interpedal macropores. Existing dual porosity functions divide pores into two categories: larger pores, controlled by structure, and smaller pores, controlled by texture. Obtaining the parameters for the structural domain is difficult due to the poor characterization of large pores. Large pores cannot be characterized from water retention curves because measurement of water retention near saturation, and CT scans of soils rely on small soil sample volumes which limits the pore characterization to tens of millimeters in range, while pores may be much larger. In this study, we developed multiple PTFs to predict the van Genuchten parameters (ɑ and n) of the structural domain in dual porosity models, as well as the w coefficient, which reflects the relative abundance of these two types of pores in the dual porosity model. Our PTFs were developed from characterized pores > 180 µm from nine pedons across Kansas, USA, using recent advances of multistripe laser triangulation (MLT) scanning applications. MLT scanning pore characterization allowed us to characterize soil pores > 10 cm and was conducted on 30-cm wide soil monoliths collected from excavation walls of each pedon that were either 20 or 40 cm tall depending on the thickness of the horizon. We used ImageJ to quantify pore-size distributions that were then used to estimate the water retention curve (WRC) and hydraulic conductivity of the structural domain. We fitted van Genuchten functions to characterize the WRCs in the structural domain, and ROSETTA 3.0 was used to characterize the WRCs in the matrix domain. These WRC fits were used to develop new PTFs that predict the parameters of the dual porosity model using mixed linear models with inputs including NRCS soil structure field descriptions along with standard physical and chemical properties (clay, sand, SOM, bulk density, coefficient of linear extensibility, cation exchange capacity, horizon midpoint depth, and quantified morphological descriptions of structural type, grade, solidity, roundness, and circularity). Using the predicted parameters, we estimated water retention for each horizon and achieved high levels of correlation and accuracy when compared with the water retention derived from the MLT scans. The approach for creating PTFs can be used to improve soil hydraulic property parameterization of soils with structure in regional hydrologic and climate models by providing a framework for integrating multiple recent advances such as the characterization of large pores using MLT and use of quantified soil structure from profile descriptions. Future studies will examine performance of these PTFs in numerical hydrologic models.

How to cite: Pachon, J., Hirmas, D., Ajami, H., Sullivan, P., Billings, S., Sena, M., Zhang, X., Li, L., Jarecke, K., Singha, K., Nippert, J., Flores, A., and Cao, X.: Visible to the eye, now in the model: Parameterizing dual porosity water retention functions in structured soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10919, https://doi.org/10.5194/egusphere-egu23-10919, 2023.

A.202
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EGU23-11699
Hammad Ullah Khan Yousafzai, Khan Zaib Jadoon, and Muhammad Zeeshan Ali

Agriculture is one of the crucial sectors of Pakistan’s economy – accounting for about 21% of GDP and engaging approximately 50% of work force and is the major source of livelihood of a substantial segment (67%) of population. Traditionally farmers use the classical methods for irrigation like flood irrigation, border irrigation, and furrow bed irrigation, which are less efficient and cause more water losses due to surface runoff and infiltration of water beyond the root zone of the crop. Furthermore, excessive pumping of water from the wells caused high consumption of energy. Due to lack of proper monitoring system for irrigation water management, farmers use more water than required water to the crop. High rate of water losses in irrigation systems is due to heterogeneity of soil in the agricultural field and water infiltration beyond the root zone of the crop.

This paper presents the calibration and field validation of soil moisture sensors for smart irrigation system using IoT (Internet of Things). Field soil samples were collected to calibrate soil moisture sensors. Different amount of water was added to oven-dried soil samples to create soil moisture variability and the voltage values of the capacitive soil moisture sensor were measured to establish a calibration curve. After the calibration of sensors, an array of soil moisture sensors was installed vertically to monitor soil moisture dynamics within the root zone of the crop. The Wi-Fi/LORA module is used to transfer the data to a cloud server at a frequency of 60sec/cycle. The data from the cloud server can be accessed via the mobile phone application “BLYNK”. Results show that the vertical dynamics of soil moisture were clearly measured by the smart soil moisture monitoring system at different depths. The calibrated sensors can be used for smart irrigation systems and can be easily adapted for different irrigation methods.

How to cite: Yousafzai, H. U. K., Jadoon, K. Z., and Ali, M. Z.: Calibration and field validation of smart soil moisture monitoring system, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11699, https://doi.org/10.5194/egusphere-egu23-11699, 2023.

A.203
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EGU23-12915
|
Conrad Jackisch and Tobias Hohenbrink

Theory in soil physics is tightly bound to integral lab observations of dynamics of soil water content and matric potential. In addition, the perceptual model of (linear) filter flow water movement is deeply embedded in measurement procedures and projections of soil water dynamics. Such Darcy-scale principles have been found to mismatch with observations and application requirements at the landscape-scale including the effect of boundary conditions. While this discrepancy is often attributed to soil heterogeneity and the requirement for effective parameterisation, we seek to discuss that assumptions about scalability of lab-measured soil hydraulic properties taken out of the capillary context of soils potentially render our "physics" ill-posed.

In this PICO we will present a series of analyses of soil water state dynamics from lab, plot and hillslope scales. We will show how scaling coincides with a change in boundary conditions and hydraulic gradients, which can fundamentally alter the inferred properties in similar soils at different locations. However, these effects are largely ignored when generalising soil-water constitutive theory and pedotransfer functions.

We propose a scale- and information aware evaluation concept for pedotransfer function derivation and application. Given the many theoretical obstacles in scaling non-linear three-phase characteristics in porous media, we argue that reducing the scale-gap between the level of derivation and application of soil physical characteristics is more promising. A smart, standardised and repeatable field experiment at the pedon scale could be a first step towards a more physically consistent reference of macroscale soil functioning.

 

How to cite: Jackisch, C. and Hohenbrink, T.: How Darcy-scale daemons lead theory developments for soil-water dynamics astray, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12915, https://doi.org/10.5194/egusphere-egu23-12915, 2023.

A.204
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EGU23-14197
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ECS
|
Matteo Rolle, Stefania Tamea, Pierluigi Claps, and Davide Poggi

The impact of climate change on agriculture is a major challenge for the food and water security of next decades. In the future, the Mediterranean area will be particularly exposed to water scarcity, which may lead to significant losses in agricultural yield. Climate projections show that many densely cultivated areas of Southern Europe will suffer decreases of precipitation intensity and frequency, with severe consequences in terms of irrigation requirements, i.e.  the amount of water needed to meet the evapotranspirative demand of crops during dry periods. Therefore, the modelling of climate-driven crop water requirements and available water resources is essential to understand future criticalities for agriculture and to adopt proper adaptation strategies.

In this study, the agricultural irrigation requirement was estimated by modeling the daily water balance in the soil, on the basis of evapotranspirative demand and precipitation, over the densely irrigated basin of Demonte, in South Piedmont (Italy). The volumes of irrigation required by local agriculture were calculated for 30 main crops, taking into account the local information of yearly distribution of crops. The available surface water in the basin was compared to the present irrigation requirements, using flow discharge data from the river that feeds the local network of irrigation channels. In order to analyze future scenarios, precipitation and temperature data from five EURO-CORDEX regional climate models were used to estimate the irrigation requirements and the available surface water for the 2035-2055 period, considering multiple RCP scenarios.

Results show that the current available water resources are little enough to meet the irrigation requirements over the Demonte basin for the months of July and August, when most of the cereals reach the maximum growing phase. The climate-driven assessment for the future decades shows that the water required for irrigation will gradually exceed the threshold of available resources, with different degrees of severity depending on the RCP scenario. Moreover, future scenarios highlight a progressive increase in the temporal lag between the period of maximum irrigation requirements (July-August) and the high-flow regime period in the hydrographic network (April-June). As a consequence, most of the surface freshwater in the Demonte basin will not be available for agriculture during summer, when most of the irrigation will be required. Modeling the future scenarios of agricultural water needs and available resources is an important step to understand the future implications of climate change on food production. Moreover, this is a valuable instrument to support proper adaptation strategies, both in terms of agricultural and water management planning policies.

How to cite: Rolle, M., Tamea, S., Claps, P., and Poggi, D.: Climate-driven local assessment of future irrigation requirements and available water resources in North-West Italy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14197, https://doi.org/10.5194/egusphere-egu23-14197, 2023.

A.205
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EGU23-14297
Jie Tian

High spatial heterogeneity, difficulty in monitoring and lack of soil hydrological processes have resulted in poor understanding of the key hydrological processes in topographically complex, high elevation mountainous areas, impeding the advancement and applications of mountainous hydrology and hydrological models. This research aims to understand the mechanism of key hydrological processes at multiple spatial scales (soil profile, hillslope, watershed, and region) in the Qilian Mountain ranges, Northwest China. To this end, an in-situ observation network has been set up to monitor the hydrological processes, including precipitation, infiltration, soil moisture, subsurface flow, evapotranspiration and runoff at the multiple spatial scales. The in-situ observations has been applied to: 1) quantify the soil moisture dynamics about infiltration, 2) gain a better understanding of the underlying hydrological mechanisms of preferential flow; and 3) understand the relationship between rainfall, soil moisture dynamics and evapotranspiration.

How to cite: Tian, J.: The multiple-scale hydrological processes observations at mountainous areas and its preliminary results, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14297, https://doi.org/10.5194/egusphere-egu23-14297, 2023.

A.206
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EGU23-16029
Stefano Barontini, Martina Siena, and Marco Peli

The soil--water redistribution is an interesting and complex process that takes place after an abundant imbibition of the uppermost soil layers, as after rainfall or irrigation. It is a consequence of the concurrency of other processes, that are downward advection and diffusion, surface evaporation and root water uptake. It is therefore simultaneously characterised by downward and upward water flow and by water extraction, and, as a consequence, it plays a key role at partitioning the water fluxes through the soil, with feedbacks also on the mass fluxes and on the soil layering.

Aiming at contributing to better understanding this process, we present a theoretical (qualitative) and a numerical assessment of some properties of the soil--water redistribution, based on the classical framework of the Richards equation.

The qualitative analysis focuses on the evolution of the soil--water content of an imbibition front, as a consequence of the onest of a continuous surface evapotranspiration. The process is analogically depicted with the traditional description of the flood--wave propagation in free--surface flow. Particularly we show that, considering an instantaneous water--content wave within the uppermost soil, an observer would meet, from the bottom moving upward, the planes where:

  • The (downward) Darcian velocity q is locally maximum in time, ∂q / ∂t = 0, where the water content θ is in imbibition;
  • θ is locally maximum, ∂θ / ∂t = 0, where q is instantaneously maximum in space, ∂q / ∂x = 0, and θ is still in imbibition;
  • θ is instantaneously maximum in space, ∂θ / ∂x = 0, where the downward flux is purely gravitational, i.e. q = K, being K(θ) the hydraulic conductivity;
  • q = 0, i.e. the zero--flux plane, that separates the downward from the upward flux, where θ is instantaneously increasing in space, ∂θ / ∂x > 0;
  • q is instantaneously minimum in time (i.e. the upward flux is maximum), where ∂θ / ∂x > 0.

Morevover an observer who follows the peak of water content would see it reducing in space and time, being its total derivative dθ / dt < 0, until it vanishes.

If the observer stops at fixed depth, these patterns would reflect in a cycle in the (θ,q) phase plane, where, starting from initially hydrostatic condition, one would observe the (local) maximum q, the (local) maximum θ, the onset of an advective flow q = K when the (spatial) peak of θ passes at that depth, the passage of the zero--flux plane, the minimum q and then the hydrostatic condition again.

The evapotranspiration is however ruled by diurnal cycles and the soil--water dynamics vary depending on the development of the root apparati. We provide an insight on these aspects by means of the numerical simulation, performed with Hydrus1d. It shows that diurnal evapotranspiration cycles induce fluctuations in the depth of the zero--flux plane and that the root water uptake, which shares the evapotranspirative demand in the whole domain, reduces the uppermost upward flux, thus allowing the zero--flux plane reaching deeper depths.

How to cite: Barontini, S., Siena, M., and Peli, M.: Qualitative and numerical results on the soil--water redistribution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16029, https://doi.org/10.5194/egusphere-egu23-16029, 2023.

A.207
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EGU23-16591
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ECS
Fenglin Zuo and Xiaoyan Li

The subsurface critical zone (CZ) structure in alpine regions has a profound influence on water storage. The primary focus of this work is to reveal that the organic layer (A), leaching-deposit layer (B), saprolite layer (C) and freeze–thaw processes regulate changes in subsurface liquid water storage (CSWS). Here, we selected six representative ecosystems along an elevation gradient (4221~3205 m) in the Qinghai Lake Basin Critical Zone Observatory (QLBCZO) on the Qinghai-Tibet Plateau. We performed in situ field surveys, ground-penetrating radar (GPR) and electrical resistivity tomography (ERT) measurements to investigate the subsurface CZ structure and liquid water storage (SWS). The results showed that the saprolite layer (thickness of 0.84~41.85 m) was the main subsurface liquid water storage reservoir, with a monthly average value of 595.49 mm. It occupied 82.12% of the total water storage of layers A, B and C. The average seasonal frozen thickness (SFT) ranged from 0.33 m to 1.60 m. SFT contributed most to CSWS, with 27.95% during the thawing period, and precipitation contributed most, with 19.87% during the freezing period. The SWS of the saprolite layers compared to that of layers A and B increased the most, by 39.41 mm and 45.88 mm in the thawing and nonfreezing periods, respectively, and that of layer B decreased maximally by 52.50 mm in the freezing period. This study contributes to advancing the mechanistic understanding of the interactions between the subsurface CZ structure and water storage processes and provides high-quality data with which coupled ecohydrological models can be developed.

How to cite: Zuo, F. and Li, X.: Subsurface Structure Regulates Water Storage in the Alpine Critical Zone on the Qinghai-Tibet Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16591, https://doi.org/10.5194/egusphere-egu23-16591, 2023.

A.208
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EGU23-15490
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ECS
Marco Peli, Stefano Barontini, Emanuele Romano, and Roberto Ranzi

Benfratello's Contribution to the study of the water balance of an agricultural soil (Contributo allo studio del bilancio idrologico del terreno agrario) was firstly published in 1961. The paper provides a practical conceptual and lumped method to determine the irrigation deficit in agricultural districts, and it generalizes previous Thornthwaite (1948) and Thornthwaite and Mather (1955) water balances thanks to the application of the dimensionless approach introduced by De Varennes e Mendonça (1958). Since then, it has been used in many areas in Southern Italy. It is our opinion that, due to its simplicity and to the small number of required parameters, Benfratello's method could be regarded to as an effective tool to assess the effects of climatic, landuse and anthropogenic changes on the soil water balance and on the irrigation deficit.

In previous contributions we presented (i) a GIS—based application of Benfratello's method to the case study of the semiarid Capitanata plane (4550 km2), one of the most important agricultural districts in Italy, and (ii) a theoretical development of the method that allows to simply estimate in closed form the uncertainity of the calculated irrigation deficit, once known the interannual variability of the required climatic variables (air temperature and precipitation). In this contribution we present the results obtained by applying the GIS—based Benfratello framework to estimate the irrigation deficit and its uncertainty of the Capitanata plane case study under different climate change scenarios.

The scenarios were generated with the following procedure: (i) combination of different GCMs (CNRM-CM5, CMCC-CM and IPSL-CM5A-MR) with the IPCC RCP4.5 and RCP8.5 scenarios as well as with historical data, (ii) statistical downscaling of the obtained models to estimate future time series of air temperature and precipitation for the meteorological stations of interest in the considered case study and (iii) spatial interpolation with ordinary kriging. The obtained maps were then used as input data for the already developed GIS—based application of Benfratello's method.

How to cite: Peli, M., Barontini, S., Romano, E., and Ranzi, R.: GIS—based application of Benfratello's method to estimate the irrigation deficit and its uncertainty under different climate change scenarios, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15490, https://doi.org/10.5194/egusphere-egu23-15490, 2023.

A.209
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EGU23-16625
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ECS
Lisa Maria Bahlmann, Kathleen M. Smits, and Insa Neuweiler

Multi-phase multi-component flow and transport models are a key instrument for analyzing and predicting gas transport inside the vadose zone. The soil moisture distribution within the vadose zone varies in time and space. Thus, accurate gas transport prediction relies on the precise knowledge of the saturation-dependency of the transport parameters such as the effective gas diffusion coefficient Deff. Although recent advances from typical small scale experiments (diffusion apparatus with typical soil core size of 100 cm3) show that Deff-saturation(S)-relationships are not only dependent on general soil characteristics such as air-filled porosity and total porosity, but can also be derived from pore network characteristics, such as pore connectivity and geometry, most model frameworks rely on simple empirical formulations such as Millington & Quirk (1961), which find wide acceptance, but have been found to not be universally applicable.

The current state of research lacks extensive performance tests for the application of Deff-S-relationships beyond the small scale and especially for realistic natural conditions, where soil moisture changes with depth and gas transport processes may be more complex than in standard laboratory setups used for the experimental determination of Deff, which leads to unknown errors in the numerical prediction of sub-surface gas transport processes.

We test different Deff-S-functions within a multi-phase-multi-component flow and transport model by reproducing a laboratory gas transport experiment, where a tracer gas is injected into a quasi-2D Darcy-scale sand tank with a soil moisture distribution that covers the full range from wet to dry and comparing simulated and measured gas concentrations at several locations within the tank over time. The systematic evaluation of different functions leads to the conclusion that the saturation-dependency of Deff in the tested sand follows power law-scaling at low gas phase saturation and linear scaling above, in line with the physically based concepts of percolation theory and effective medium theory and with recent experimental results (Ghanbarian et al., 2018). Other approaches such as (Buckingham, 1904; Penman, 1940; Millington & Quirk, 1961; Moldrup et al., 2000) lead to large errors between numerical and experimental results. We demonstrate that the use of an inaccurate Deff-S-function can lead to a misrepresentation of diffusion coefficients by a factor of up to 105, which underlines the need for a correct representation of the saturation-dependency of Deff in numerical modeling of sub-surface gas transport.

How to cite: Bahlmann, L. M., Smits, K. M., and Neuweiler, I.: Evaluation of gas diffusion-saturation functions as inputs to multiphase flow and transport models simulating gas transport in variable saturated sand, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16625, https://doi.org/10.5194/egusphere-egu23-16625, 2023.

Posters virtual: Wed, 26 Apr, 16:15–18:00 | vHall HS

Chairpersons: Roland Baatz, Stefano Ferraris, Martina Siena
vHS.27
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EGU23-7389
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ECS
Vaibhav Gupta and Sekhar Muddu

Soil hydraulic parameters such as residual water content, saturated water content, hydraulic conductivity, are key factors to be considered when assessing the soil capabilities to provide ecosystem services. Proper computation of fluxes from vadose zone using the hydrological models strongly depends on correct estimation of input parameters, process scale, boundary, and initial conditions. Estimation of soil parameters for many hydrological models is always an arduous task due to uncertainty bounded with parameters. Over the last few years many researchers have favoured to estimate the parameters using inversion approach due to increasing computing capabilities and easily measurable output variables. The current study deepens the understanding of the soil hydraulic parameter estimation using inversion approach. The inversion was conducted on synthetic data set using the SWAP (Soil water atmosphere and plant) model along with the GLUE (Generalized Likelihood Uncertainty Estimation) algorithm. Several constrain variables, able to be derived from remote sensing or in-situ measurements (Leaf Area index - LAI, Evapotranspiration – ET and Surface soil moisture – SSM), were used in the inversion process alone or in different combinations. The current study uses the two types of soil profile, homogenous soil system and two layered soil system. In this synthetic experiment, we compared the effect of different soil type, different surface conditions, different water conditions, and frequency of observed variables on parameter estimation. Effect of initial predefine range of the parameter space, on SHP estimation, were also investigated. Use of DSM data to define the initial range of parameter space were also investigated. We also simulated the state variables with uncertainty using the estimated parameters. Main outcomes could be reported when retrieving the SHPs, retrieval was significantly correlated with soil type and water stress condition, although overall retrieving performances were quite poor specially in layered soil system. We could identify some promising combinations of constrain variables for better estimation of parameter in different soil types. Our approach may further provide spatial sampling of DSM data components to improve the SHPs estimation, to be used as surrogate input for defining the initial range.

How to cite: Gupta, V. and Muddu, S.: Uncertainty in estimation of Soil Hydraulic properties and root zone state variables in inverse method, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7389, https://doi.org/10.5194/egusphere-egu23-7389, 2023.

vHS.28
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EGU23-15657
A simplified agro-hydrological model for the computation of water fluxes and irrigation efficiency in rice areas
(withdrawn)
Arianna Facchi, Michele Rienzner, Giovanni Ottaiano, Giulio Gilardi, and Claudio Gandolfi