Session 1 | Innovative geophysical sensing methods in hydrological and critical zone research

Session 1

Innovative geophysical sensing methods in hydrological and critical zone research
Conveners: Paolo Nasta, Karsten Høgh Jensen
Orals
| Mon, 12 Jun, 09:15–10:50|Saints Marcellino and Festo
Poster
| Attendance Mon, 12 Jun, 10:50–11:30|Poster area, Attendance Mon, 12 Jun, 16:15–17:15|Poster area
Orals |
Mon, 09:15
Mon, 10:50
All current hydrological observatories distributed are providing soil moisture data from in-situ and proximal sensor network systems in different spatial and temporal resolutions. Moreover large-scale global coverage of soil moisture data is provided by various remote sensing platforms. The increase in the amount of soil moisture data across spatial and temporal scales is leading to the era of “Big Soil Moisture Data”. The exponential growth in computational power and advancements in machine learning algorithms are unlocking scientific insights at an unprecedented rate in soil-moisture-related processes leading to improved hydrological, ecological and agricultural modeling and forecasting. Yet the abundant soil moisture data collected by new-generation ground-based, airborne-based and space-borne platforms are still affected by uncertainties and have gaps in both space and time. In this session, we welcome contributions that analyze soil moisture dynamics that have been made available in hydrological observatories aiming at improving our understanding of hydrological processes. We also invite contributions that address the aforementioned challenges.

Invited speaker: Yann Kerr, France (yann.kerr@cesbio.cnes.fr)

Orals: Mon, 12 Jun | Saints Marcellino and Festo

09:15–09:30
09:30–09:40
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GC8-Hydro-7
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Session 1
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Nick van de Giesen, Hessel Winsemius, Frank Annor, Tomáš Fico, Eugenio Realini, Remko Uilenhoet, and Salvador Peña-Haro

TEMBO Africa is a project funded by the European Commission that seeks to fill some of the many geo-data gaps in Africa. Specifically, TEMBO Africa will produce operational data products for rainfall, river flow, soil moisture, bathymetry, and open water. With these products, new services will be developed for reservoir management, germination insurance, and flood early warnings. The products will be the result of the combination of innovative in situ sensors, satellite observations, and environmental models. There will be at least seven innovative in situ sensing methods involved, namely X-band rainfall radars, neutron counting for soil moisture based on natural boron, commercial microwave links, camera-based velocimetry, bathymetry with fish finders, raindrop intervalometers, and GNSS level sensors. TEMBO Africa is transformative in that it aims to reduce the total costs of ownership of the geo-services to less than 10% of present costs. We do not only look at the capital costs of the sensors but also at reduction of maintenance cost and the availability and development of human resources. For this reason, co-development is essential to ensure that context specific challenges are addressed. In this presentation, we highlight the general design approach and early results.

The work leading to these results has received funding from the European Horizon Europe Programme (2021-2027) under grant agreement n° 101086209. The opinions expressed in the document are of the authors only and no way reflect the European Commission’s opinions. The European Union is not liable for any use that may be made of the information.

    TEMBO Africa 

 

How to cite: van de Giesen, N., Winsemius, H., Annor, F., Fico, T., Realini, E., Uilenhoet, R., and Peña-Haro, S.: TEMBO Africa: New sensors and geo-services for water management and agriculture , A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-7, https://doi.org/10.5194/egusphere-gc8-hydro-7, 2023.

09:40–09:50
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GC8-Hydro-31
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Session 1
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Detlef Lazik, Gerrit de Rooij, and Mohammad Hashar

There is a large discrepancy between the spatial extent of a catchment and the volume or area covered by a single sensor, particularly for sensors operating below the soil surface. Especially in the unsaturated zone, spatial heterogeneity combined with the very small soil volume represented by a data point (often 1 cubic decimeter or less), this contrast necessitates vast sensor networks that are costly to maintain and generate large quantities of data that require extensive processing to provide information useful at scales relevant for land and water management.

Over the past years, we developed a technology to measure the concentration of selected gases in soils by burying gas-permeable, flexible tubes of up to tens of meters of length in the soil at desired depths and flushing them with a gas of known composition (e.g., dry air). Pressure changes observed during short intervals during which the gas flow is stopped can be used to derive the difference in partial pressures of a target gas inside the tube and in the soil surrounding the tube. After processing, this gives the average concentration of the target gas in the soil surrounding the entire length of the tube. The technology is operational for CO2, and will be employed in a forest ecosystem to measure soil respiration in real time.

By specific choices of the tube material, the composition of the flushing gas, and the reference system, the measurement system can be adapted to other gases. If the target gas is water vapor, the relative humidity (RH) of soil air can be measured. According to first laboratory results this results in a measure of the area-averaged soil water content assuming local phase equilibrium between water vapor and liquid soil water. In very dry soil, e.g., in arid and hyper-arid regions, the RH of the soil air drops measurably. In this case the averaged matric potential of the soil water can be monitored in situ in a range far beyond that of water-filled tensiometers.

The presentation will explain the set-up of the system, showcase completed trials and elaborate on on-going plans for CO2-concentration measurements in a forest soil. 

How to cite: Lazik, D., de Rooij, G., and Hashar, M.: An innovative membrane-based sensor technology for large-scale measurements of gas concentrations in the subsurface, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-31, https://doi.org/10.5194/egusphere-gc8-hydro-31, 2023.

09:50–10:00
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GC8-Hydro-33
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Session 1
Simone Noto, Andrea Petroselli, Flavia Tauro, Ciro Apollonio, and Salvatore Grimaldi

Scientific interest in ephemeral streams increased in the last decades, but monitoring their dynamics remains a major challenge in hydrology. Motivated by the last advancements in computer vision techniques, we propose an optical-based and non-invasive low-cost approach to provide a continuous estimation of the water level fluctuations. The system comprises a consumer grade wildlife camera with near infrared (NIR) night vision capabilities and a target pole set in the thalweg. The water level estimated through a simple white pole is compared to estimations obtained through different types of targets, such as broader coloured bars, with the aim to identify the optimal stage-cam setup. The feasibility of the approach is demonstrated through a set of benchmark experiments performed in natural settings with different illumination conditions and during rainfall events. Our findings show that broader bars enhance the visibility of the target but also increase the reflection effect of the water. Therefore, using the stage-cam configuration comprising the narrow target and optimizing the parameters involved in the image analysis procedure may be sufficient to monitor water level dynamics.

How to cite: Noto, S., Petroselli, A., Tauro, F., Apollonio, C., and Grimaldi, S.: Monitoring wet stream dynamics in ephemeral streams: stage-cam system experimental evidence, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-33, https://doi.org/10.5194/egusphere-gc8-hydro-33, 2023.

10:00–10:10
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GC8-Hydro-46
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Session 1
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Mathias Herbst, Lennart Böske, and Eva Falge

To understand and predict soil moisture dynamics it is essential to take the role of the vegetation into account. For example, hydrological processes in agricultural soils are strongly affected by seasonal vegetation dynamics in terms of rooting depth and root distribution. Here we present a new approach to monitor and model root dynamics and its influence on soil moisture in the critical zone using mini-rhizotrons combined with phenological observations.

The setup in the field observatory consists of a portable root scanner connected to a tablet computer and a number of acrylic glass tubes with a diameter of two inches that are inserted into the soil at the start of the growing season of selected crops. 360-degrees-scans of soil and roots are taken regularly at different depths in the tubes. Root parameters such as length, diameter, surface and density are identified automatically from the data for each soil layer. Complementary observations of aboveground plant phenology, obtained either by visual inspection in-situ or by remote sensing techniques, are related to the root parameters.

Results from mini-rhizotron data collected at two observatories in Germany show that vertical root distribution and maximum rooting depth in agricultural soils, which varies with plant species and phenology, weather patterns, soil type and management, irrigation etc., are crucial parameters to explain the observed temporal variability and vertical gradients in soil moisture satisfactorily. Deriving these parameters from above-ground phenology and incorporating them into a soil water model led to a significant improvement when compared to a model version based on reference rooting depths from the literature. Thus, we argue that mini-rhizotrons constitute a useful supplement to hydrological observatories and can help understand and predict soil moisture dynamics in the critical zone.

How to cite: Herbst, M., Böske, L., and Falge, E.: Observing spatio-temporal variations in rooting depth and density as a control factor for soil moisture dynamics, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-46, https://doi.org/10.5194/egusphere-gc8-hydro-46, 2023.

10:10–10:20
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GC8-Hydro-56
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Session 1
Improved extraction of hydrologic information from geophysical data during an artificial hillslope infiltration
(withdrawn)
Benjamin Mary, Konstantinos Kaffas, Matteo Censini, Francesca Sofia Manca di Villahermosa, Andrea Dani, Matteo Verdone, Federico Preti, Paolo Trucchi, Daniele Penna, and Giorgio Cassiani
10:20–10:30
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GC8-Hydro-91
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Session 1
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Lena Scheiffele, Katya Dimitrova-Petrova, Maik Heistermann, Till Francke, Daniel Altdorff, and Sascha Oswald

Cosmic ray neutron sensing (CRNS) allows for the estimation of root-zone soil water storage at the hectare scale. Therefore, CRNS can be valuable assets of long-term hydrological observatories aimed at unravelling key hydrological processes beyond the point scale. One such observatory is the cluster established within the Cosmic Sense project, situated within the ATB research site in Marquardt, NE Germany, and probably the best-equipped CRNS field laboratory so far. Here we present an overview of datasets which uniquely combined three years of observations (2019-2022) from a dense CRNS cluster with a wealth and variety of supplementary measurements. The long-term operating CRNS cluster (8 permanently installed sensors) was complemented with (i) short-term measurements of additional stationary CRNS, expanding the cluster footprint, (ii) rover CRNS campaigns as well as (iii) a dedicated irrigation experiment which was monitored by a cross-scale combination of sensors, including UAV and CRNS roving. Alongside the CRNS, insights on soil water storage states and fluxes were gained by long-term measurements of profile soil moisture (at 27 locations, up to 105 cm depth), soil water tension (up to 200 cm depth), groundwater and surface water levels (3 locations along the hillslope) and GNSS-R (Global Navigation Satellite Systems reflectometry). Snapshot information of near-surface water storage dynamics were obtained by UAV-based remote sensing. Furthermore, Electrical Resistivity Tomography profiles along the hillslope supplied a 3D view of water storage distribution in depth. Ground truthing campaigns, ancillary measurements of biomass and soil properties helped  capture the spatial distribution of these properties  and made the interpretation of the soil water content data more robust. Overall, the Marquardt cluster is unique in its combination of a dense CRNS cluster along with the long ongoing operational period of more than three years and the wealth of additional hydrometerological data. Additionally, the 3-year data-set captures a wide range of wetness conditions, from prolonged dry spells to heavy rainfall events and snow episodes. Therefore, such a comprehensive dataset, combining innovative techniques with traditional hydrometeorological measurements gives the opportunity to investigate a range of research questions. Those could be related, but not limited to, the study of dominant flow paths and hydrological connectivity during heavy rainfall; the suitability of sensor combinations to best study water storage dynamics in a heterogeneous landscape and the retrieval of spatial soil water storage patterns using a CRNS cluster and ancillary data.

Cosmic Sense Official University of Potsdam Webpage https://www.uni-potsdam.de/en/cosmicsense/

How to cite: Scheiffele, L., Dimitrova-Petrova, K., Heistermann, M., Francke, T., Altdorff, D., and Oswald, S.: First multi-year cosmic-ray neutron sensing cluster: insights from three years of soil water storage observations across depths and scales at an agricultural research site  in North-East Germany, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-91, https://doi.org/10.5194/egusphere-gc8-hydro-91, 2023.

10:30–10:40
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GC8-Hydro-73
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Session 1
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Sascha E. Oswald, Sebastian Rothermel, Gabriele Baroni, Anna Balenzano, Henrik Kjeldsen, Martin Schrön, and Miroslav Zboril

One of the key environmental variables and essential climate variable is soil moisture, with its high relevance for applications such as agriculture, forestry, water management including hydrometeorological extreme events or hydrological modelling. Yet accurate measurement of soil moisture is limited by its high natural spatiotemporal variability, given spatially (vertically and horizontally) variable hydraulic properties of soil, and events that are highly variable themselves (in time, extension and intensity).

One geophysical method to close the gap between point-scale measurements and satellite-based remote sensing is Cosmic Ray Neutron Sensing (CRNS). Its integration area of about 0.1 km² is above the coverage of wireless sensor networks and at least when combined to CRNS clusters can cover several pixels of high resolution satellite remote sensing, e.g. by the ESA Sentinel-1 Earth Observation mission. We combine these three methods to bridge the scales in monitoring of soil moisture, and this within a novel metrological framework on validation and standardization.

The basis for that is an EU-wide collaboration project of 18 institutions called SoMMet[1]. Its approach is to thoroughly establish CRNS as a bridging method at intermediate scale by linking it to point-scale soil moisture sensors with certification according to newly established metrological standards while testing a range of CRNS detector designs in facilities for neutron metrology. The aim is to achieve an improved comparability and reliable estimates of uncertainty and provide recommendations on network design and validation practices, which shall result in a more widespread transfer into remote sensing applications and hydrological modelling.

A central component is to conduct field comparison and testing campaigns covering the different scales at three high-level field sites across Europe. One of the candidate sites is located close to Potsdam, Northern Germany. Having evolved from temporary soil moisture field campaigns it hosts the sole long-term CRNS cluster (currently 15 CRNS probes) that covers a conjoined area. This is somewhat similar to wireless in-situ sensor networks, but working non-invasively, with partially overlapping footprints and last not least on larger scale, here about 0.6 km² altogether. We will present examples of SoMMet field test sites, and especially first results of this CRNS cluster from 2023 in its recently extended coverage set-up that now brings it further up to satellite remote sensing resolution.


[1] Acknowledgment: The project 21GRD08 SoMMet has received funding from the European Partnership on Metrology, co-financed from the European Union’s Horizon Europe Research and Innovation Programme and by the Participating States.

How to cite: Oswald, S. E., Rothermel, S., Baroni, G., Balenzano, A., Kjeldsen, H., Schrön, M., and Zboril, M.: A novel combined approach for bridging scales in spatiotemporal soil moisture monitoring applying metrological principles, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-73, https://doi.org/10.5194/egusphere-gc8-hydro-73, 2023.

10:40–10:50
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GC8-Hydro-90
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Session 1
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ECS
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Markus Köhli, Patrick Stowell, Jannis Weimar, Patrizia Ney, Felix Nieberding, Ulrich Schmidt, Heye Bogena, and Klaus Görgen

Accurate soil moisture (SM) measurements are key in hydrological observations and subsequent applications as it can greatly improve our understanding of soil processes. Recently, Cosmic-Ray Neutron Sensors (CRNS) have been recognized as a promising tool in SM monitoring due to its large footprint of several hectares and half a meter in depth. The key characteristic feature of the method is the exceptionally high moderation strength of hydrogen, which makes it nearly independent of the soil chemistry. CRNS has a great potential for irrigation and monitoring applications as to the non-invasive nature of the method and the low-maintenance, independently operating sensors. From the initial focus on hydrological research. CRNS are increasingly used in agriculture, e.g. irrigation management and soil moisture mapping, and have been integrated LoRa or NB-IoT networks for fast data transmission. Two projects are discussed which advance CRNS technologies into monitoring networks.

COSMIC-SWAMP aims to provide an open-source water monitoring platform that integrates cosmic ray sensing data with FiWare Smart Application compliant analysis routines. Extending the existing Smart Water Management Platform (swamp-project.org), COSMIC-SWAMP supports dynamic processing of multiple co-located cosmic ray sensor streams to support automated and continuous growth forecasting using Wageningen/WOFOST crop models.

ADAPTER involves the development and provision of innovative simulation-based information products. Addressing weather- and climate-resilient agriculture, daily and comprehensive long-term weather and soil information are made available to the agricultural community and all interested parties as easy-to-use analyses, data products, and information interfaces (adapter-projekt.org). The hydrological model ParFlow coupled to its Common Land Model (CLM) module provides a nationwide water balance prediction with 600 m spatial resolution. The data assimilation within the product platform is supported by an independent network of CRNS stations (12 agricultural locations in North Rhine-Westphalia).

This contribution provides an overview about the current state of the art in CRNS methodological integration, neutron detection technology and development of IoT interfaces with measurements and forecasts focusing on the water balance, including groundwater.

How to cite: Köhli, M., Stowell, P., Weimar, J., Ney, P., Nieberding, F., Schmidt, U., Bogena, H., and Görgen, K.: CRNS-based monitoring technologies as solutions for climate-resilient agriculture, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-90, https://doi.org/10.5194/egusphere-gc8-hydro-90, 2023.

Poster: Mon, 12 Jun, 10:50–11:30, 16:15–17:15 | Poster area

P1
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GC8-Hydro-26
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Session 1
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Isabelle Braud and Jérôme Gaillardet

The OZCAR (Critical Zone Observatories network) Research Infrastructure (RI) brings together several observatories documenting the critical zone, the thin pellicle on the Earth's surface between the non-weathered rocks and the lower atmosphere, which is the living environment of living beings. These long-term observatories were historically created in France to answer specific scientific questions such as the impact of rainfall acidification on forests, the genesis of extreme floods or the understanding of nitrate pollution. They monitor different compartments of the critical zone (atmosphere, soil, surface water, groundwater, cryosphere, wetlands, biosphere, etc.) through the measurement of a large number of meteorological, hydrological, hydrogeological, geochemical, surface fluxes and vegetation dynamics variables.

The aims of OZCAR RI are:

  • i) To foster data sharing with the scientific community through the development of a common data portal;
  • ii) To promote the use of the collected data in models;
  • ii) To allow the development and deployment of new measurement techniques, taking advantages of large projects funded by the French government such as the CRITEX project (Innovative equipment for the critical zone, 2011-2022) and the TERRA FORMA project (Designing and testing a smart observatory of socioecological systems in the Anthropocene, 2021-2029), that aim at deploying innovative measurements to document the critical zone and design new observatories in the Anthropocene;
  • iv) To favor interdisciplinary researches through dedicated calls.

The observatories, and their counterparts at the European scale gathered in eLTER RI, are highly instrumented sites where new measurement techniques can be tested and deployed, where hydrological functioning hypotheses can be assessed through the exploitation of data and models. These observatories are also good places to addressing some of the 23 unsolved problems in hydrology. The presentation will illustrate the value of a network of critical zone and hydrological observatories through examples of researches conducted in the OZCAR RI network.

https://www.ozcar-ri.org/

https://www.critex.fr/critex-3/observatories/

https://terra-forma.cnrs.fr/

https://elter-projects.org/

How to cite: Braud, I. and Gaillardet, J.: The OZCAR Critical Zone Observatory Network: an opportunity to enhance hydrological research through sites, data and model sharing, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-26, https://doi.org/10.5194/egusphere-gc8-hydro-26, 2023.

P2
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GC8-Hydro-28
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Session 1
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Robert Horton, Tusheng Ren, Joshua Heitman, Yili Lu, and Yongwei Fu

Recent advancements in fine-scale thermo-TDR measurements of soil thermal and electrical properties provide opportunities to measure state variables in soil (temperature, water content, ice content, and air-filled porosity), soil properties (bulk density, thermal diffusivity, volumetric heat capacity, thermal conductivity, and bulk electrical conductivity) and energy and mass fluxes in soil (sensible heat, latent heat for evaporation or freezing, infiltrating liquid water, and upward moving liquid water).  It is also possible to estimate soil hydraulic properties from thermo-TDR thermal property and electrical property measurements. This presentation will include laboratory and field investigations that demonstrate the usefulness of thermo-TDR measurements to characterize heat and mass transfer properties and fluxes in soil.

How to cite: Horton, R., Ren, T., Heitman, J., Lu, Y., and Fu, Y.: Measuring Soil Properties and Processes with Thermo-Time Domain Reflectometry Sensors, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-28, https://doi.org/10.5194/egusphere-gc8-hydro-28, 2023.

P3
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GC8-Hydro-36
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Session 1
Gabriele Baroni, Stefano Gianessi, Riccardo Mazzoleni, Cinzia Alessandrini, Claudio Gandolfi, Orietta Cazzuli, Francesca Ragazzi, Stefano Ferraris, Davide Canone, Christian Ronchi, Roberto Cremonini, and Secondo Barbero

Over the last decades, several new observation systems have been developed, tested, and implemented in dedicated experimental sites by research groups in many countries all around the World. The data collected at these high-level test sites have boosted research and collaborations providing the basis for new hypothesis testing, better process understanding and model improvements. In contrast, national and more operational ground monitoring networks are still largely based on traditional instruments. Moreover, the different networks and the data are not always well integrated, even at the regional level. For these reasons, the capability to monitor the main components of the hydrological cycle over large areas is still limited and the observation systems to support the management of the water resources and for environmental protections can be improved. By using soil moisture and snow water equivalent monitoring as examples, in this contribution we present and discuss challenges, results and opportunities in upgrading national weather stations and improving the service provided by the public environmental agencies. Specifically, the difficulties of implementing ground monitoring networks are first discussed. The opportunities provided by the development of new non invasive sensors based on cosmic-ray neutrons detection are then presented. The activities and the results conducted during the last years to move this technology further from research to operation are shown. The current uptake from a number of Italian environmental agencies is reported. The key components and current challenges for a successful implementation are finally discussed.

How to cite: Baroni, G., Gianessi, S., Mazzoleni, R., Alessandrini, C., Gandolfi, C., Cazzuli, O., Ragazzi, F., Ferraris, S., Canone, D., Ronchi, C., Cremonini, R., and Barbero, S.: Upgrading standard weather station with cosmic ray neutron sensors in Italy: challenges, results, and opportunities., A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-36, https://doi.org/10.5194/egusphere-gc8-hydro-36, 2023.

P4
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GC8-Hydro-47
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Session 1
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ECS
Victor Gauthier, Anna Leuteritz, and Ilja van Meerveld

Overland and subsurface flow are major runoff processes but remain poorly understood for pre-Alpine catchments with low permeability soils. The connectivity of these near-surface flow pathways leads to quick changes in streamflow during events. However, their occurrence is highly variable in both space and time, and depends on the geomorphological setting and event characteristics. Therefore, the aim of the TopFlow project is to investigate the generation and connectivity of overland flow and shallow subsurface flow in a Swiss pre-Alpine catchment.

We installed runoff plots at 14 locations inside a 20-ha catchment to measure overland flow and shallow (up to ~40 cm) subsurface flow during two summers: 2021 and 2022. In addition, we used homemade electrical resistance sensors to detect near-surface flow and saturation and we measured groundwater levels and soil moisture. The plots are located at different topographic locations and under different vegetation. In this presentation, we will present our first results on the occurrence of the overland flow and shallow subsurface flow and relate them to the topographic position and rainfall- and antecedent wetness conditions.

How to cite: Gauthier, V., Leuteritz, A., and van Meerveld, I.: When does near-surface flow occur in a pre-Alpine headwater catchment?, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-47, https://doi.org/10.5194/egusphere-gc8-hydro-47, 2023.

P5
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GC8-Hydro-51
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Session 1
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ECS
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Cosimo Brogi, Heye Reemt Bogena, Vassilios Pisinaras, Markus Köhli, Olga Dombrowski, Harrie-Jan Hendricks Franssen, Andreas Panagopoulos, Johan Alexander Huisman, Konstantinos Babakos, and Anna Chatzi

Given the expected increase of droughts related to climate change, soil moisture (SM) monitoring will likely become essential for farmers as it helps to reduce water consumption while mitigating crop losses. Cosmic-Ray Neutron Sensing (CRNS) is a promising SM monitoring method that is based on the negative correlation between fast neutrons originating from cosmic radiation and SM content. As CRNS integrates SM over a large radius of ~130-210 m with a penetration depth of ~15-85 cm, it has advantages over point-scale and remote-sensing methods. However, it is yet unclear how well CRNS can monitor areas with complex SM heterogeneity, such as small irrigated fields. In this study, two CRNS equipped with a novel gadolinium oxide thermal shielding were installed in two small (~1.2 ha) irrigated apple orchards located in the Pinios Hydrologic Observatory (Greece). Each CRNS was supported by an Atmos41 all-in-one climate station, by water meters measuring irrigation timing and amounts, and by a network of 12 wireless SM measurement nodes (SoilNet) that monitored SM at 5, 20 and 50 cm depth. The results showed that the CRNS was sensitive to the weekly irrigation events, but that it showed a general underestimation of the magnitude of SM fluctuations caused by the irrigation, which resulted in a RMSE of 0.058 cm3 cm-3. To better understand these results, we used the URANOS model to simulate neutron transport for a CRNS placed in the centre of a square irrigated field of varying dimensions (0.5 to 8 ha). The simulation results showed that CRNS can be used to monitor irrigation in fields as small as 0.5 ha in certain SM conditions and that a gadolinium-based thermal shielding provides the best monitoring results due to the much-reduced detection of thermal neutrons. Nonetheless, a considerable number of detected neutrons (above 60%) can originate outside the target field if the irrigated field is small, and in such cases a CRNS may not be able to clearly distinguish irrigation from SM variations in the surroundings. In an attempt to correct for such SM variations not related to irrigation, an additional SoilNet node was installed outside one of the two irrigated apple orchards in September 2021. By combining the results of neutron transport simulations with the information provided by this additional SoilNet node, a correction of CRNS-derived SM was developed that better captures both timing and magnitude of SM changes (RMSE reduced to 0.031 cm3 cm-3). These results show that the combination of real-world studies with neutron transport simulations can help to establish CRNS as a reliable tool in irrigation management.

How to cite: Brogi, C., Bogena, H. R., Pisinaras, V., Köhli, M., Dombrowski, O., Hendricks Franssen, H.-J., Panagopoulos, A., Huisman, J. A., Babakos, K., and Chatzi, A.: Potential and limitations of cosmic-ray neutron sensors for irrigation management in small fields, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-51, https://doi.org/10.5194/egusphere-gc8-hydro-51, 2023.

P6
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GC8-Hydro-67
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Session 1
Daniel Altdorff, Ségolène Dega, Hendrik Paasche, and Martin Schrön

Upscaling of soil water content (SWC) information towards the large-scale (>10 km) is highly desired to address the increasing demand on SWC products at various sectors. Random forest (RF) regression has been suggested as suitable method to generate large SWC maps from a limited amount of observations. RF deals with multiple prediction variables (predictors) to derive the missing values of a desired variable (e.g. SWC) based on their internal relationship. Cosmic ray neutron sensing (CRNS) is an alternative method for passive SWC mapping and monitoring, either by stationary CRNS sensors or by mobile CRNS roving. CRNS has a certain advantage over most classical hydrogeophysical approaches because of its footprint at the hectares-scale and beyond, particularly true for roving data, which qualifies CRNS data as suitable input for RF regressions. However, commonly CRNS roving data contain a high amount of noise and outlier values, related to the statistical distribution of neutron counting, which hinders the signal interpretation and could lower the quality of the RF regression performance. There are so far two ways to overcome the noise problem and to achieve a higher data stability; i) increasing of the aggregation time, which decreases the signal uncertainty but also reduces the spatial resolution and ii) applying smoothing algorithms, e.g. interpolation or moving averages, which results in more stable values, but it does not solve the outlier problem.

We used SWC data from CRNS roving along the Selketal catchment at the Harz mountain, Germany, to test the performance of a score criteria for an adaptive removal of potential outliers. The score criteria are internal test parameters, providing an indication about the probability of values that might be an outlier or not. Therefore, each observation was subject to a group of queries, asking its conformity to the surrounding values by selected statistical parameters. Based on the total score of the queries, the potentially unreliable observations were removed using various thresholds and used as input for the RF regression. RF regression was performed using static (e.g. topographical indices, soil properties) and dynamic (precipitation) predictors generating SWC maps from an area of ~2700 km². SWC input data were split into training (~2/3) and validation sets (~1/3).

Preliminary results showed that the application of the score criteria resulted in more stable spatial pattern and improved the R² from 0.099 to 0.196, 0.266 and 0.308 for score 6, 4 and 3, respectably. Achieved root mean squared error also decreased with stronger filtering, ranging from 0.14 for the original datasets to 0.078 for score 3. However, by using the score 3 threshold, 22.4% of the data were omitted. Hence, an optimization between the amount of excluded data and the resulting improvement of prediction needs to be developed and tested. The implementation of the spatial relationship in-between the observations and a weighting of the score values according to their importance should further increase the performance. Due to its easy application and its adjustable criteria selection, the proposed filtering approach has the potential to become more popular in CRNS roving studies.

How to cite: Altdorff, D., Dega, S., Paasche, H., and Schrön, M.: Improvement of soil moisture regionalization based on random forest regression by applying score criteria for mobile cosmic-ray neutron sensing data, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-67, https://doi.org/10.5194/egusphere-gc8-hydro-67, 2023.

P7
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GC8-Hydro-85
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Session 1
Jonathan Evans, John Bloomfield, Gemma Coxon, Simon Teagle, Wouter Buytaert, Matt Fry, Lucy Ball, Ali Rudd, James Sorensen, Nick Chappell, Thorsten Wagener, and Gareth Old

Here we present the UK vision for new world-leading hydrological observation networks and sensor innovation test beds that will provide the long-term datasets needed to enable the mitigation of the impacts of hydrological extremes. Plans are underway for a Floods and Droughts Research Infrastructure (FDRI). This represents a major capital investment expected to be funded by the UK Research and Innovation Infrastructure Fund and delivered through the Natural Environment Research Council (NERC) at an estimated cost of £38m. FDRI is urgently needed to make the UK more adaptable and resilient to floods and droughts. It will include major new hydrological catchment instrumentation, with innovative technology to provide observations of key components of the terrestrial water cycle, and in-field facilities for trialling and developing new sensing technologies. Extensive community consultation and reviews have identified key science questions that are being used to inform infrastructure design. Successful impact will be enabled through strong investment in digital infrastructure to achieve a hydrological data commons. Integrated near real-time datasets will be publicly accessible, consolidated and inter-operable, ready for application specific analysis and modelling. As FDRI planning develops, there are opportunities to design-in the latest thinking on catchment monitoring strategies with innovative sensing, and to ensure that long-term hydrological datasets will be able to answer a wide variety of future research questions.

How to cite: Evans, J., Bloomfield, J., Coxon, G., Teagle, S., Buytaert, W., Fry, M., Ball, L., Rudd, A., Sorensen, J., Chappell, N., Wagener, T., and Old, G.: A Vision for Transformative Hydrological Monitoring – Planning for the UK Floods and Droughts Research Infrastructure (FDRI), A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-85, https://doi.org/10.5194/egusphere-gc8-hydro-85, 2023.

P8
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GC8-Hydro-89
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Session 1
Paolo Nasta, Heye Bogena, Alexander Huisman, Benedetto Sica, Carolina Allocca, Ugo Lazzaro, Caterina Mazzitelli, Harry Vereecken, and Nunzio Romano

In the Upper Alento River Catchment (UARC; southern Italy), two test sites, having different physiographic and soil features, were instrumented with SoilNet wireless sensor networks controlling GS3 (METER Group, Inc. USA) capacitance sensors deployed at soil depths of 15 and 30 cm at twenty locations to monitor soil permittivity, soil temperature, and apparent electrical conductivity. The conversion of soil permittivity into soil water content is challenging given the high clay content of the soil. Therefore, the both factory and Topp’s calibration functions are compromising soil water content dynamics with underestimated dynamics during dry periods and overestimations in the wet season. In addition, the soil moisture measurements is influenced by the very strong soil temperature variations. In this study we combined a laboratory calibration with in-situ intensive validation campaigns. The laboratory calibration of GS3 electromagnetic sensors was carried out on repacked soil samples by simultaneously measuring soil permittivity and soil water content at prescribed temperature steps within the range observed in the field (from 4.5 °C and 31.9 °C). A new empirical regression-based calibration law was developed for the two study areas to relax the impact of soil temperature on the measurement of soil permittivity. The temperature-corrected approach was validated in the field by taking thermo-gravimetric measurements of soil water content using a stainless steel soil core sampler over five field campaigns at soil depths of 15 and 30 cm. Our results demonstrated that the proposed site-specific calibrations properly reflect the seasonal dynamics of observed soil water content and outperform both factory and Topp’s calibration functions.

How to cite: Nasta, P., Bogena, H., Huisman, A., Sica, B., Allocca, C., Lazzaro, U., Mazzitelli, C., Vereecken, H., and Romano, N.: Temperature-corrected calibration of GS3 dielectric sensors, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-89, https://doi.org/10.5194/egusphere-gc8-hydro-89, 2023.

P9
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GC8-Hydro-99
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Session 1
Paolo Castiglione and Gaylon Campbell

Dielectric sensors have been used for decades to monitor soil water content. While such measurements are straightforward for insulations, they may be challenging for electrically conductive materials. As a result, the performance of soil moisture sensors based on capacitance technology rapidly decreases with soil salinity. In alternative, dielectric permittivity and electrical conductivity may be estimated at once and very accurately by measuring the complex impedance of the sample. We present a new method for measuring the complex impedance, which can be implemented with very inexpensive circuitry. The resulting dielectric measurements are shown to be accurate for conductivity up to 20 dS/m. We will present preliminary results in soilless material and discuss the benefits of accurate dielectric measurements in greenhouse applications. 

How to cite: Castiglione, P. and Campbell, G.: Complex dielectric measurements permit accurate estimate of soil water content in saline environments., A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-99, https://doi.org/10.5194/egusphere-gc8-hydro-99, 2023.

P10
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GC8-Hydro-105
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Session 1
Enrico Gazzola, Luca Stevanato, Luca Morselli, and Paul Arnaud

It is of the utmost importance to know the water content in a soil, or soil moisture, for its role in triggering destructive events. In recent years, soil moisture has been recognized as a key information to improve wildfire predictions, proving more reliable than predictions based on weather data. Accumulation of water in slopes can reduce cohesion and friction thus triggering landslides and mudslides, while indeed the water quantity in the form of snow (SWE – Snow Water Equivalent) is responsible for avalanches.

Cosmic Ray Neutron Sensing (CRNS) technology provides unique capabilities to determine water content in soil, snow, and biomass by filling the gap left by current methods in term of scale and depth. A single, autonomous probe placed over the ground, requiring little maintenance, is able to provide real-time data on a large scale (hectares), in deep (tens of cm in soil, meters in snow).

The new generation of CRNS probes allows the contextual detection of muons, which provides detailed information about variations of the local flux of incoming cosmic rays. Previous probes rely on a public network of reference stations to monitor flux variations, with the closest station possibly being hundreds of km away from the site and the data availability being reliant on an external entity. On situ monitoring of the incoming flux is therefore a key improvement of the method reliability.

In 2022 ANAS, the Italian company responsible for road infrastructures, funded a Proof-of-concept project called MY-LAND, with the aim of verifying on field the capability of CRNS probes to support risk assessment. In the framework of this project, FINAPP installed two CRNS probes for large-scale soil moisture measurement along the Longarone - Belluno Smart Road, obtaining data that were used together with hydrological models of the area to assess the risk of landslides or flash floods. The first probe was installed in Acquabona (Cortina d’Ampezzo), where a high risk of debris flows is expected, and the second in Perarolo di Cadore, where a landslide is considered a threat to the town.

Two significant landslide events were observed in the sites during the experiment. Results show how CRNS technology, when supported by the knowledge of specific hydrological models of the land and weather forecast, is able to provide a valuable contribution to risk assessments and decisional processes.

How to cite: Gazzola, E., Stevanato, L., Morselli, L., and Arnaud, P.: Improving the prediction of extreme events with new-generation CRNS probes, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-105, https://doi.org/10.5194/egusphere-gc8-hydro-105, 2023.

P11
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GC8-Hydro-108
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Session 1
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ECS
Giuseppe Francesco Cesare Lama and Mariano Crimaldi

The proper analysis and prediction of the hydrodynamic interaction between water flow and vegetation covering natural and manmade vegetated rivers are among the main objectives of Ecohydraulics. Riverine and riparian plants have a paramount impact on flow resistance and water quality associated with vegetated water bodies. Also, the presence of vegetation considerably affects the mean and turbulent flow fields with important implications on oxygen production and nutrient transport within vegetated open channels. In this perspective, the use of advanced field and remote sensing techniques to measure the most relevant features of plants constitutes a stimulating open research window. The interplay between riparian vegetation and water flow in vegetated water bodies has a key role in the dynamic evolution of aquatic and terrestrial ecosystems in wetlands and lowlands. The present study analyzes the effects of the spatial distribution of reed (Phragmites australis (Cav.) Trin. ex Steud.) beds, an invasive riparian species extremely widespread in wetland and lowlands worldwide, on the main hydraulic and hydrodynamic properties of an abandoned vegetated reclamation channel located in southern Italy. A field campaign was carried out to obtain Leaf Area Index (LAI) and Normalized Difference Vegetation Index (NDVI) of reed beds through both ground-based and Unmanned Aerial Vehicle (UAV) methodologies, and to correlate them to the channel’s flow dynamic and water quality main features. Hydrodynamic simulations of the vegetated reclamation channel were performed and validated based on the experimental measurements of the hydraulic and vegetational parameters acquired in the field to build up a robust model to be employed also in future Ecohydraulic research. The evidence of this study constitutes useful insights into the quantitative analysis of the correlation between the spatial distribution of riparian vegetation stands in natural and manmade vegetated water bodies and their hydrodynamic and water quality main features. The outcomes of the present work can be seen as stimulating new viewpoints to be taken into account for the proper management of biomass belonging to riparian and riverine vegetation developing within vegetated water streams.

 

How to cite: Lama, G. F. C. and Crimaldi, M.: On the Key Eco-hydrodyanmic Features of Vegetated Rivers: a Case Study in southern Italy, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-108, https://doi.org/10.5194/egusphere-gc8-hydro-108, 2023.

P12
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GC8-Hydro-120
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Session 1
Majken Looms, Søren Julsgaard Kragh, Rena Meyer, Karsten Høgh Jensen, and Mie Andreasen

The cosmic-ray neutron (CRN) probe has successfully been used to estimate soil moisture time series at various soil and land cover types across several climatic zones. Previous studies also demonstrate the value of mobile CRN campaigns (i.e. roving) for soil moisture mapping. However, the published study locations have mainly been homogeneous in terms of land cover and soil type. At such conditions, simple on-site calibration using small-scale soil samples can be sufficient. Nonetheless, soil sampling is typically time-consuming, is not always possible and/or is not necessarily representable of the true conditions. Furthermore, measured neutron intensities are dependent on all the hydrogen pools within the footprint, primarily soil moisture, but also litter layer and biomass. Thus, calibration using 100+ soil samples for each point along the survey route is necessary in highly heterogeneous agricultural landscapes. The requirement of such spatiotemporal calibration has hindered a full embracement of the CRN roving method. Neutron sensors with multiple energy sensitivities, here named dual-spectra CRN, can instead be combined to separate the influence of various hydrogen pools.

In this work, we used a dual-spectra CRN rover to collect data along a 34.5 Km NE-SW line in Denmark (approximately 176 line Km) at an average speed of 29 Km/h. The data was collected biweekly from December 2018 to May 2019 resulting in 12 campaigns in total. The dual-spectra averages of each campaign correlate to the SMAP soil moisture product, with a higher correlation for purer signals of thermal and epithermal neutron counts. Furthermore, the epithermal neutron intensity and thermal-to-epithermal ratio maps are dependent on the land cover type enabling the use of a simple and robust methodology to obtain spatiotemporal soil moisture maps using these multiple signals. The estimated spatiotemporal soil moisture values are within expected ranges and are not as the neutron signal dependent on land cover. Instead, the average soil moisture appears to be dependent on the estimated hydraulic conductivity map for the area.

How to cite: Looms, M., Kragh, S. J., Meyer, R., Jensen, K. H., and Andreasen, M.: Mapping spatiotemporal soil moisture in highly heterogeneous agricultural landscapes using mobile dual-spectra cosmic-ray neutron probes, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-120, https://doi.org/10.5194/egusphere-gc8-hydro-120, 2023.

P13
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GC8-Hydro-130
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Session 1
Roland Baatz, Patrick Davies, Heye Bogena, Emmanuel Quansah, and Leonard K. Amekudzi

Soil moisture is a critical hydrological variable affecting rainfall-runoff processes, regulating net ecosystem exchange, and an essential agricultural variable that constrains food production. Soil water deficiency results in water stress to plants, causing a reduction in biomass and yield production. Thus, assessing soil moisture conditions and estimating the effects of drought or water excess are relevant and important information associated with a decline in agricultural yield. This study analyses time series data of the Cosmic Ray Neutron Sensor (CRNS) to estimate soil moisture in three different climatic zones with distinct seasonal dynamics. The CRNS allows non-invasive and continuous monitoring of soil moisture by detecting the neutrons generated by cosmic rays that mainly interact with the hydrogen atoms in soil water. This study demonstrates an improved CRNS signal processing to enhance the temporal accuracy and overall signal-to-noise ratio by observing sub-daily soil moisture changes. In particular, this study investigates the effectiveness of the Moving Average (MA), Median filter (MF), Savitzky-Golay (SG) filter, and Kalman filter (KF) to minimize errors in soil moisture estimates at distinct points in time. We anticipate the improved signal-to-noise ratio to benefit CRNS applications such as the detection of rain events at the sub-daily resolution, provision of SM at the exact time of a satellite overpass, and irrigation applications.

How to cite: Baatz, R., Davies, P., Bogena, H., Quansah, E., and Amekudzi, L. K.: Improving Soil Moisture Monitoring from Cosmic Ray Neutron Sensors under Various Climate Conditions, A European vision for hydrological observations and experimentation, Naples, Italy, 12–15 Jun 2023, GC8-Hydro-130, https://doi.org/10.5194/egusphere-gc8-hydro-130, 2023.