The Simplified Evaporation Method (SEM) is widely used to simultaneously determine the water retention curve (WRC) and hydraulic conductivity curve (HCC) of soils. However, its application is traditionally restricted to the suction range measurable by tensiometers. To overcome this limitation, we incorporated humidity sensors into the setup of the SEM, enabling measurements of soil water potential in the hygroscopic range. This advancement allows for the measurement of a quasi-continuous time series of soil water suction from full saturation to air dryness, which allows to determine the WRC across this range and the HCC from field capacity to air dryness. We term this approach the eXtended Simplified Evaporation Method (XSEM).
We tested the XSEM on three soil types—silt loam, sandy loam, and sand—and compared its results with those from the dew point method (DPM) and inverse modeling, observing strong agreement among the methods. Key advantages of the XSEM include (i) simultaneous determination of both hydraulic functions using a single experimental setup and straightforward calculations, (ii) reduced effort for WRC determination at suctions above 10⁴ cm compared to the DPM, (iii) high-resolution outputs, and (iv) a fully automated protocol. In particular, XSEM provides a realistic assessment of film and vapor flow contributions to the HCC, which dominate water flux in porous media at low water content. These advancements improve the modeling of soil water dynamics and actual evaporation rates in dry soil.
How to cite: Bosse, J., Durner, W., Iden, S. C., Sut-Lohmann, M., and Peters, A.: Determination of soil hydraulic functions across the full moisture range by extending the simplified evaporation method using humidity sensors, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18091, https://doi.org/10.5194/egusphere-egu25-18091, 2025.
Pressure infiltrometer (PI) experiments are commonly applied for determination of field-saturated soil hydraulic conductivity, Ks, by the analysis of steady-state infiltration rate from within a single ring. Basically, two approaches can be used for determining Ks: the One-Ponding-Depth (OPD) approach, that uses a single depth of ponding and requires an a priori estimate of the α* parameter, and the Two-Ponding-Depth (TPD) approach, that allows simultaneous estimation of Ks and α*, the ratio between Ks and matric flux potential. Recently, SATURO infiltrometer (METER Group, Inc., USA) was developed as an automated version of the PI method. SATURO automatically calculates Ks by the TPD equations but its functioning presents some specific peculiarities. In particular, the higher pressure head on the soil surface is established before the lower one, and the steady-state infiltration rates required for TPD calculation are sampled after a soaking phase and one or more pressure cycles.
A field test of SATURO infiltrometer was conducted on two sandy-loam soils at Acerra (ACE) and Villabate (VIL) and a clay soil at Monreale (MON). A total of 55 automated SATURO experiments (12 at ACE, 25 at MON and 18 at VIL sites) were conducted and the results compared with those obtained from manual PI tests under comparable conditions in terms of ring diameter and depth of insertion and pressure head values.
Independently of the device (PI or SATURO), the TPD approach yielded Ks values that were not statistically different from those obtained by applying the OPD approach with site-specific α* values of 16, 5.2 and 9.6 m-1 for ACE, MON and VIL, respectively. When a first approximation literature value of α* = 12 m-1 was used, Ks calculated by the OPD approach was overestimated on average by 43.9% at MON site but much lower discrepancies were observed at the other two sites, thus confirming that this choice is not expected to introduce large uncertainties in the calculated Ks values.
At ACE, SATURO yielded a mean Ks value numerically similar (D = 4%) and not significantly different from the PI. At MON, the mean of Ks obtained with the PI was larger by 68% than that obtained with SATURO and the differences were statistically significant. At VIL, the mean of Ks obtained with the PI was significantly larger than that obtained with SATURO and the two means differed by 80%. According to the similarity criterion by Elrick and Reynolds (1992), this investigation suggested an acceptable agreement between the two methods given the means of Ks were statistically similar or differed by no more than 1.8 times.
Acknowledgement: This study was carried out within the RETURN Extended Partnership and received funding from the European Union Next-GenerationEU (National Recovery and Resilience Plan – NRRP, Mission 4, Component 2, Investment 1.3 – D.D. 1243 2/8/2022, PE0000005) and the Ministero dell’Università e della Ricerca of Italy, project PRIN 2022 "Smart technologies and remote Sensing methods to support the sustainable agriculture WAter Management of Mediterranean woody Crops (SWAM4Crops)" CUP B53D23018040001.
How to cite: Autovino, D., Vincenzo, B., Basile, A., Caltabellotta, G., De Mascellis, R., Fusco, M., and Iovino, M.: Evaluation of Saturo infiltrometer for determining field-saturated soil hydraulic conductivity , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9008, https://doi.org/10.5194/egusphere-egu25-9008, 2025.
Permafrost thawing is a common natural phenomenon in cold regions, where it has significant impacts on ecosystem stability and the sustainability of human society. This study elucidates the melting process of frozen soil and the importance of water content during the thawing process at the pore scale based on nuclear magnetic resonance (NMR) investigations. Additionally, thermodynamic theory is applied to interpret the link between the pore ice melting process and the NMR T2 relaxation signals. The NMR signal intensity has been used to estimate the thawing degree of frozen soil, however, the mechanism underlying the shift in the T2 signal peak has not been revealed. In this study, a pre-freezing thawing experimental platform was established to capture pore-scale characteristic thawing (temp gradient -30oC, -20oC, -15oC, -10oC, -5oC, -3oC, -2oC, -1oC, 0oC, 1oC, 5oC, 15oC) of four different loess soil samples with various saturation levels ranging from 25% to 100%. The results show that the T2 distribution clearly demonstrates three distinct thawing mechanisms in frozen soil thawing: (1) surface water melting corresponds to an increase in the T2 peak amplitude; (2) bulk water melting corresponds to a broadening of the T2 peak; (3) pore water migration from large pores to small pores corresponds to a shift in the T2 peak. Furthermore, measurements from unsaturated samples (25%, 50%, 85% saturation) provide insights into the importance of water content in the thawing process. Collectively, our method for interpreting thawing behaviors of soil provides a non-invasive and high-resolution method to understanding the dynamic soil-water behaviors in cold regions and can further help establish advanced freeze-thaw induced landslides monitoring framework.
Keywords frozen soil; pore ice; melting mechanism; nuclear magnetic resonance; loess
How to cite: Wang, Z., Zhang, C., Zhang, Y., and Li, B.: Thawing mechanism of frozen loess soil based on a nuclear magnetic resonance study, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1038, https://doi.org/10.5194/egusphere-egu25-1038, 2025.
Soil hydraulic properties, SHP, are crucial to simulate water movement in agro-environmental systems. However, directly measuring SHP at large scales is time-consuming and costly. As an alternative to direct measurements, pedotransfer functions, PTF, can estimate SHP from other easily-measurable soil physical properties. Many PTFs were developed in the literature but the majority are empirical and rely on the textural information to obtain the hydraulic properties without accounting for the soil structure, which plays a significant role in the hydraulic conductivity. Recently, a new physically-based PTF was developed, called bimAP. It is a bimodal extension to the unimodal physically-based Arya-Paris PTF, unimAP, by explicitly accounting for the aggregate-size distributions to predict the bimodal SHP, improving the ability to reproduce the spatial variability of SHP. Saturated hydraulic conductivity, K0, is then calculated by applying Kozeny-Carman model, whose parameters are estimated from the upper part of the water retention curve, WRC, near saturation. To practically apply the bimAP PTF, a dynamic Excel spreadsheet is presented along with the instructions to use it. When introduced with the soil physical parameters and the scaling parameter, αAP, the spreadsheet can carry out the calculations to obtain the ratios of the macropores and the matrix to overall porosity, and hence, the bimodal WRC. The spreadsheet also includes the calibration of the αAP when the user introduces measured soil hydraulic parameters; using the Excel solver, the sum of square differences between the measured and estimated soil water contents can be minimized to calibrate αAP. Excel solver can then be used to fit the upper part of the resulting bimAP WRC by optimizing the Brooks-Corey water retention parameters, which are then used to calculate K0 by applying Kozeny-Carman model. Eventually, the entire bimAP WRC can be fitted by optimizing Durner water retention parameters also using the Excel solver. Estimating αAP, in the absence of measured SHP, is also possible from the soil physical parameters: particle-size distribution, aggregate-size distribution, dry bulk density, single-aggregate bulk density and the ratio of macropores to the overall porosity, by means of multiple linear regression.
How to cite: Hassan, S. B. M., Comegna, A., Dragonetti, G., and Coppola, A.: Application of a bimodal physically-based pedotransfer function with a user-friendly spreadsheet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8945, https://doi.org/10.5194/egusphere-egu25-8945, 2025.
The sensitivity of infiltration rate to antecedent moisture content (AMC) in wettable soils is well-established with a low AMC promoting a higher initial infiltration rate. For water repellent soils, such as those found on fire-affected landscapes, we know little about how AMC may affect infiltration. Here we seek to understand how AMC affects infiltration for sub-critically water repellent soils (soils for which water forms a contact angle <90°). We conducted laboratory experiments using uniform #40-70 quartz sand with different degrees of water repellency from which we development a process-based model for simulating sorptivity and infiltration rate as a function of AMC. The experiments exhibited a highly non-linear relationship between contact angle and initial saturation degree (as a direct measure for AMC). We found the observed contact angle of water repellent sand was highest for air-dry conditions (as expected) but decreased rapidly with increasing initial saturation degree (AMC). Sorptivity of water repellent sand (which integrates wettability, pore sizes and AMC), exhibited a local minimum at the air-dry condition; a maximum for initial saturation degrees between 3% and 6%; then again a local minimum for initial saturation degree near 40%. Using the developed model along with measured contact angles and associated sorptivity values, maximum infiltrates were associated with an initial saturation degree around 5%. Thus, for water repellent soils, the maximum infiltration rates are associated with slightly moist rather than air-dry AMC. Model simulations also agreed well, qualitatively, with field-measured sorptivity data collected from a fire-affected, water repellent loam in Wyoming, USA. This research was supported by the U.S. National Science Foundation under Grant Nos EAR‐1324894 and OIA-2148788 as well by the US Army Corps of Engineers under Grant Numbers DACW42-03-2-0000 and W912HZ17C0037.
How to cite: Berli, M., Shillito, R. M., Or, D., Giovando, J., Pak, J., Pradhan, N., Floyd, I. E., and McKenna, S.: The influence of antecedent moisture content (AMC) on infiltration into water repellent soil: Laboratory experiments and model calculations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13946, https://doi.org/10.5194/egusphere-egu25-13946, 2025.
Soil moisture data from arrays of vertically-aligned sensors have been used in various ways to detect the occurrence of preferential flow (PF) in the unsaturated zone. Many such data are available at only a few depths, often 5 or fewer, and at fairly long time intervals, often 15 minutes or more. Some soil-moisture networks provide data of substantially greater resolution. One of these, the National Ecological Observatory Network (NEON) in the United States, provides soil moisture data at many locations over 18 ecoregions at 1-minute intervals, at as many as 8 depths, and as deep as 2 m. Evaluated with regard to soil moisture dynamics, such high-resolution data make it possible to go beyond the basic occurrence or nonoccurrence of PF to learn about its dynamic qualities: the magnitude and character of PF within distinct soil horizons, its transformation at layer boundaries, its interactions with soil matrix material, and the depth and duration of its influence. In some cases the rate of change of water content over small depth intervals can permit quantification of fluxes at various positions within the soil profile so that these fluxes can be evaluated with respect to the concurrent intensity and cumulative quantity of water input at land surface.
Investigation of these quantities and qualitative behaviors for identified storm periods at selected NEON locations confirms some of the prevailing expectations about PF, while also revealing new or unexpected features of potential importance. These results provide a strengthened basis for needed improvements in least two types of predictive hydrologic models: (1) for predicting the occurrence of PF in response to site characteristics and varying conditions of soil and weather, and (2) for realistically representing the PF component in general-purpose multi-domain models of flow in the unsaturated zone.
How to cite: Nimmo, J. R.: High-resolution soil moisture data reveal dynamics of preferential flow, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13982, https://doi.org/10.5194/egusphere-egu25-13982, 2025.
We tested three expressions for the unsaturated soil hydraulic conductivity curve (UHCC): Kosugi’s model (KGV), an additive model (ADV), and a junction model (JUV). KGV generalizes the Mualem-van Genuchten model and assumes that all liquid soil water flows through capillaries. ADV adds the hydraulic conductivity of water films adsorbed onto the solid surface to the conductivity of the capillaries. The recently introduced JUV has a junction matric potential at which a wet branch with a capillary conductivity function joins a dry branch with a film conductivity function. All models assume water vapor flow is driven by diffusion. We fitted the three models to hydraulic conductivity measurements for a sandy loam, a silt, and a loamy sand. Akaike’s Information Criterion suggested potential overparameterization in ADV, which has up to seven fitting parameters, whereas KGV and JUV have up to six. From the fitted curves, we generated look-up tables that were then used as input for the Hydrus-1D model for soil water flow.
We evaluated the functional performance of the three models by numerically modeling unsaturated flow in uniform vegetated columns of the three soils exposed to 10 years of generated weather records that represent three climates (monsoon, temperate, and semi-arid). The surface flux, transpiration, and bottom boundary flux were aggregated over 5-day, 10-day, and 30-day time windows, and their extremes and seasonal fluctuations were evaluated. JUV and KGV converged for all nine combinations of soil and climate, while ADV crashed three times, particularly for the sandy loam. In addition to the robustness of the three UHCC models, the presentation will highlight how the calculated fluxes and water balances agree or differ between the models.
How to cite: Nambiar, A. and de Rooij, G. H.: Evaluating Unsaturated Hydraulic Conductivity Models for Diverse Soils and Climates: A Functional Comparison of Additive, Junction, and Kosugi Parameterizations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4286, https://doi.org/10.5194/egusphere-egu25-4286, 2025.
Water availability, quality and security are major constraints on the long-term sustainable production of irrigated crops. The quality of native and imported water resources is declining in many regions which will potentially have severe adverse impact on irrigated agriculture including vineyards. We estimated water demand for irrigated vineyards in the Barossa (rainfall 440 mm) and Eden valleys (rainfall 599 mm) using the FAO-56 dual crop coefficient approach for six common soil types (sand over clay, shallow soil on rock, cracking clays, hard red brown, calcareous and gradational soil, and acid and shallow soil on rock) under the current (2000-2023) and future climate projections (2023-2051, RCP 4.5). A multi-component major ion chemistry model (UNSATCHEM) was used to investigate the long-term impact of various irrigation water sources (river, recycled, groundwater and their blends) on the four soil quality indicators (pH, EC, SAR and ESP) in different soils and the relative yield reduction in response to rootzone salinity. The model was equilibrated with the measured soil solution and exchange parameters for 72 years (1951-2023) to achieve a quasi-equilibrium state for each of the soil types. Management options such as leaching irrigation and gypsum use were also explored to mitigate the adverse impacts of the irrigation sources.
The modelled grapevine irrigation requirement varied with climate and soil types; and water demand increased significantly (10-45%) across the soil types under future climate projections. This drove an increase in regional water demand (28-32%) under future climate projections. A long-term risk assessment with the poorest quality water showed a grapevine yield reduction of 3-12 and 11-23%, with recycled and groundwater irrigation, respectively. These water sources increased the EC > 10dS/m, after 5-10 years of irrigation in the Barossa valley but maintained the soil salinity below the tolerance threshold for grapevines in the Eden valley, demonstrating the importance of higher rainfall for leaching salts.
Even irrigation with high quality river water can have the potential to increase exchangeable sodium percentage (ESP) above the threshold level (6%) for degradation of some soil types. Maximum levels of average rootzone SAR (6.5-18mmol/L1/2) and ESP (14-52%) were observed under groundwater irrigation of cracking clay soils. The acid soil over rocks showed lower sodicity hazard than sand over clay, calcareous and gradational and hard red brown soils. Model simulations suggested that an annual leaching irrigation of 30mm in spring with good quality water and subsequent irrigaiton with recycled water (1.8dS/m) or groundwater (3.3dS/m) reduced the salinity below the grapevine tolerance level. However, leaching irrigation alone was not sufficient to ameliorate the irrigation induced high sodicity hazard. A soil ameliorant such as gypsum along with leaching irigation are needed to reduce the sodicity hazard.
Modelling predictions demonstrated that availability and quality of water resources has the potential to impact grapevine yield and soil quality indicators. Management options such as leaching irrigation and gypsum application are crucial for enhancing the long term sustainability of vineyards; but maintaining a secure source of good quality water is also important to support the wine industry in the study region.
How to cite: Phogat, V. and Petrie, P. R.: The sustainability of irrigation water sources for vineyards in the Barossa Valley, South Australia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14602, https://doi.org/10.5194/egusphere-egu25-14602, 2025.
The Yellow River Delta, with shallow groundwater levels, is a vital land reserve in Eastern China. However, high groundwater salinity limits soil remediation and crop growth, necessitating effective management. While shallow groundwater contributes significantly to global vegetation transpiration (~23%), its role in saline areas remains unclear. This study introduces the Groundwater Advantage Zone (GWAZ) concept to optimize groundwater use. Through field monitoring, lab experiments, model simulations, and water isotope analysis, the research aims to: 1) Identify critical water table depths by examining spatial and temporal patterns influenced by soil, climate, and regional factors; 2) Study water and salt stress on crops, focusing on root water uptake under salinity stress and groundwater subsidence; 3) Simulate soil water and salt dynamics to quantify the GWAZ as a new index; and 4) Use the GWAZ index to optimize water tables for salinity control and groundwater use. The findings offer strategies for sustainable soil and water management, supporting agricultural development in the Yellow River Delta and similar regions.
How to cite: Zhao, Y.: Mechanisms and Synergetic Technologies for Groundwater Advantage Zone in Saline Farmland of the Yellow River Delta, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2608, https://doi.org/10.5194/egusphere-egu25-2608, 2025.
Groundwater recharge in mountainous regions is predominantly driven by snowmelt. However, shifting precipitation patterns and changes in freeze-thaw cycles due to climate change alter hydrological processes. To better understand the influence of ice dynamics in seasonally frozen soils on groundwater recharge, we evaluate two numerical models that include ice formation and melting within the soil. Specifically, we aim to quantify the partitioning of rain- and meltwater into lateral runoff and vertical infiltration.
We focus on the models PermaFOAM and PFLOTRAN, which both solve the Richards equation for unsaturated flow coupled to heat transfer equations, while using different approaches to account for ice buildup in the pore space. We apply the two models to a simplified two-dimensional hillslope cross-section, analyzing how these formulations influence hydraulic conductivity and lateral flow generation in seasonally frozen soils.
As a next step, we plan to integrate a snowpack as a porous medium into the vadose-zone model framework, enabling a comprehensive analysis of the interplay between snowmelt, soil freezing, and preferential water flow. Our goal is to improve the understanding of water flow dynamics under transient freeze-thaw conditions in soils and overlying snowpacks. By integrating snowmelt processes into hydrological models, we aim to improve the accuracy of groundwater recharge projections in mountainous regions.
How to cite: Hermann, A., Drews, R., and Cirpka, O.: Effects of Melting and Refreezing Ice in Unsaturated Soils on Groundwater Recharge, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3211, https://doi.org/10.5194/egusphere-egu25-3211, 2025.
Soil moisture plays a critical role in the growth process of rice, directly influencing crop growth and yield. This study focuses on how meteorological factors (net radiation, air temperature, and potential evapotranspiration) and plant factors (crop coefficient) impact the daily depletion of soil moisture across different growth periods of rice. The research is based on observational data from the second rice cropping season, 2023, in Guanyin District, Taoyuan City, Taiwan. A multiple linear regression model was developed to incorporate plant and meteorological factors and their influences on soil moisture at various depths. Additionally, a one-dimensional heat conduction model was utilized to analyze the interactions within the soil-plant-atmosphere continuum (SPAC) system. The results indicate that rice roots significantly impact the daily depletion of soil moisture at a depth of 20 cm. In comparison, the influence of meteorological factors stabilizes at depths of 30 to 40 cm. By integrating soil moisture data with meteorological and plant factors, this study compared the estimated thermal diffusivity and damping depth using a multiple linear regression model with values derived from in-situ soil temperature observations. The results show consistency, further validating the model's accuracy in assessing the influence of meteorological factors at various depths. This conceptual model improves the understanding of soil moisture, plant, and atmosphere interactions in rice growth. It also provides a robust scientific basis for estimating the daily depletion of soil moisture using plant and meteorological factors, which informs the optimization of water resource management and irrigation strategies customized to different growth periods. This research aims to enhance irrigation water use efficiency by providing dynamic changes in soil moisture, contributing to better water resource management and sustainability in rice agriculture.
Keywords : Soil Moisture; Multiple Linear Regression Models; One-Dimensional Heat Conduction Model; Depth Effects; Rice Growth
How to cite: Chang, Y.-T., Chen, P.-Y., and Chen, C.-C.: Establishing a Multiple Linear Regression Model Relating the Meteorological and Plant Factors to Soil Moisture at Various Depths, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5317, https://doi.org/10.5194/egusphere-egu25-5317, 2025.
Various studies have investigated the effects of grazing on soil hydraulic properties (SHPs) under different soil and environmental conditions, and grazing management practices, across different regions of the world. However, despite a relatively large body of research on this topic, the overall influence of grazing on SHPs across diverse contexts remains ambiguous due to the complex interplay of factors that moderate these effects. This study adopts a multi-level meta-analytic model to systematically collate and analyse global field data, obtained from the literature (comprising 74 papers), to investigate the magnitude of changes in SHP as influenced by grazing, moderated by 17 factors relating to management (grazing intensity, duration, strategy, livestock type, rooting depth), climate, and intrinsic soil physical properties (texture, clay content, clay type fraction and related mechanical properties). The moderating factors were obtained from details reported in the publications, as well as from independent globally distributed databases (the clay property database by Ito and Wagai (2017), with clay mechanical properties derived from equations provided in Lehmann et al. (2021)); the WorldClim 2.1 dataset (Fick and Hijmans, 2017) for mean annual rainfall and temperatures; germplasm databases for individual species listed in the publications to obtain rooting depth). Our findings showed that grazing significantly affects soil structure, causing decreased saturated hydraulic conductivity, Ksat (56%), mean infiltration rates, MIR (38%), and macroporosity, MP (10%), and an increase in bulk density, BD (28%). The meta-analysis reveals that the impact of grazing on SHPs is significantly greater under heavy grazing (for MIR, BD), long-term grazing (Ksat, BD), in areas dominated by shallow-rooted pasture compared to mixed or deep-rooted systems (BD, MP), and in cattle dominated grazing systems as opposed to sheep or mixed grazing systems (Ksat, BD, MP). Additionally, the negative effects of grazing increase with increases in mean annual precipitation (all SHP) and temperature (all, but not BD). It is also notable that clay type properties, specifically derived mechanical properties, also showed significant relationships with grazing effects, across all SHPs. The findings suggest that future research should be focused on the long-term effects of cattle grazing on soils with large fractions of active to moderately active clay types in climates with high precipitation to help develop grazing management and planting strategies that support sustainable grazing while mitigating negative soil hydrological impacts.
Fick and Hijmans (2017), DOI: 10.1002/joc.5086; Ito and Wagai (2017), DOI: 10.1038/sdata.2017.103; Lehmann et al. (2021), DOI: 10.1029/2021GL095311
How to cite: Wang, Y., Bishop, J., Verhoef, A., and Hammond, J.: A multi-level meta-analysis on the effects of grazing on soil hydraulic properties under variable grazing management, climate and clay properties, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6222, https://doi.org/10.5194/egusphere-egu25-6222, 2025.
Soil hydraulic properties (SHP) are among the indicators of the diversity and health of an
ecosystem and are commonly measured by two criteria: infiltration and water retention capacity.
This may be seen as an “Ecological Alteration,” resulting from the sum biological and non
biological processes which modify the structure of the soil, including bioturbation and the
accumulation of organic matter. These changes in soil structure drive the changes in SHP.
Central Chile has seen an abrupt and extensive land use/land cover transition from several
hundred years of wheat cultivation (annually tilled) to short rotation (~25-30 yr) silviculture.
This allows for neighboring assessment of soil impacts of transitioning from cultivated to
uncultivated production as a function of time. Further, the region’s climate geography (a North
South primary axis) allows us to view the soil health impacts of this change in planting along a
precipitation gradient (850 – 1700 mm/yr) to help tease-out the impact of climate on temporal
dynamics of soil properties.
We measured infiltration in five recently transitioned first rotation locations along this
precipitation gradient. Sampling plots were established for continuous wheat, early-, mid-, and
late-stage pine plantations, and Chilean Native Forest. We sampled in both the dry summer
months and again in the wet winter months. In the dry sampling period, we found transitions
from wheat to silviculture saw an initial decrease in infiltration; however, over time (~30 years)
infiltration in the plantations approached that of the Native Forest (increasing approximately by
an order of magnitude in 30 years). In the wet sampling period, the results were more
inconclusive. Some plots did not show an increase in infiltration capacity while others showed a
gradual increase over the same 30-year period.
How to cite: Tippett-Vannini, M. and Selker, J.: Ecologically Driven Alteration of Soil Hydraulic Properties through mono-culture Reforestation in Central Chile, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7340, https://doi.org/10.5194/egusphere-egu25-7340, 2025.
Soil evaporation is an essential component of the hydrological cycle. Within soil science, the fundamental mechanisms involved in soil evaporation are well-documented. However, within the realm of land surface modelling, the coarse spatial resolution and limited available computational resources result in a simplified representation of this highly non-linear process.
Here, we evaluated the current representation of soil evaporation within the RMI evapotranspiration and surface turbulent fluxes (ET-STF) model applied in the frame of the EUMETSAT Satellite Applications Facility on support to Land Surface Analysis (LSA SAF, http://lsa-saf.eumetsat.int/). We highlighted the discrepancies between the simplified representation of soil evaporation and the soil physical solution. To achieve this, synthetic experiments were performed using Hydrus as a reference for comparison with the LSA SAF ET-STF model. Additionally, a comparison was made with formulations in other land surface models (Surfex, ECLand & GLEAM), the resulting texture-dependent bias was demonstrated and impact of sub-grid heterogeneity was shown. Finally, an updated formulation was presented and evaluated using in situ observations.
Though widely recognised as one of the fundamental processes in the hydrological cycle, the perspective on soil evaporation is very different in soil physics compared to land surface modelling. Here, we attempted to harmonize both approaches in a pragmatic manner.
How to cite: De Pue, J., Barrios, J. M., Moutier, W., and Gellens-Meulenberghs, F.: Contrasting perspectives on soil evaporation in soil science and land surface modelling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11756, https://doi.org/10.5194/egusphere-egu25-11756, 2025.
Mulching and incorporation of crop residues (CR) into soils is a common strategy to sustain soil carbon stocks and to regulate water losses via bare soil evaporation. To date, implementing the effect of mulching strategies into soil-plant- atmosphere models remain challenging due to limited information about their effect on hydraulic properties (HP), namely the water retention and unsaturated hydraulic conductivity curve and the temporal dynamics of the process.
In this laboratory study, we measured the HP of a loamy soil mixed with maize CR to different contents (0, 2, and 5 weight-%) and a mulch layer (100 weight-% CR) from saturation to oven dryness. We differentiated between leaves and roots CR and adapted the simplified evaporation method to measure the hydraulic properties of 100 % CR layer. The experiments run as triplicates and were repeated after three weeks of incubation under optimum condition (30 °C, 90 % RH) to simulate organic matter degradation after harvest. Comparing the HP before and after incubation provided information about the temporal effect of CR on soil HP.
Compared to the control, water retention was systematically increasing about 2 to 5 vol.-% for the CR-soil mixtures and up to 50 vol.-% for the 100 % CR samples over a broad suction range from pF 0 to pF 3. The effect was most pronounced for leaves. The unsaturated hydraulic conductivity of all CR-soil mixtures was not affected. In contrast, the 100 % CR samples provided measurements of unsaturated hydraulic conductivity around pF 1 which were by an order of magnitude lower compared to the CR-soil mixtures. Incubation of the samples significantly reduced the carbon content of the samples and changed the structure of the CR but surprisingly, a positive effect on the soil water retention curve was still measurable.
The study shows that the beneficial effect of CR incorporation on the soil HP of a loamy soil increases with the amount of CR and that the effect lasts for a period of at least one month after harvest. This period is crucial to define the starting condition of the following crop. In addition, the lower unsaturated hydraulic conductivity of a 100 % CR layer confirmed field observations where a mulch layer reduces water losses through bare soil evaporation.
How to cite: Leuther, F., Langanki, A., and Diamantopoulos, E.: A lab study to quantify the effect of fresh and degraded crop residues on soil hydraulic properties, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12090, https://doi.org/10.5194/egusphere-egu25-12090, 2025.
Understanding the mechanisms governing the infiltration of precipitation into soil is crucial in eco-hydrological processes. However, the effect of vegetation types on the wetting front depth and velocity is poorly understood. Here, we analyzed 1234 infiltration events based on a large-scale long-term in-situ soil moisture monitoring network in arid mountainous area of northwest China. Our results show that the proportion of preferential flow was the largest in shrub (52.38%), followed by alpine meadow (36.55%), grassland (11.51%), and barren (0.70%). The wetting front velocity was consistent with the order of the proportion of preferential flow, with values of 11.42, 4.96, 2.32, and 1.16 cm/h, respectively. The mean velocity of preferential flow events was 2.05 times (0.06–71 times) higher in the shallow soil layer and 3.86 times (0.3–68 times) higher in the deep soil layer compared to matrix flow events. The wetting front depth was shallowest in alpine meadow (14.31 cm), followed by barren (15.70 cm), grassland (18.95 cm), and shrub (39.81 cm). Moreover, the wetting front depth and velocity reach their peak values in summer, primarily influenced by precipitation. Random Forests analysis results demonstrate that preferential flow is the primary factors influencing the profile wetting front depth, with control factors varying across different soil depths, soil water characteristic curve in shallow soil layers, and vegetation in deep soil layers, respectively. Meanwhile, soil organic carbon emerged as the most important factor impacting wetting front velocity. These findings contribute to a deeper understanding of infiltration processes in arid mountainous areas and offer a theoretical foundation for refining and enhancing mountain hydrological models.
How to cite: Xue, D., Tian, J., Zhang, B., Kang, W., Zhou, Y., and He, C.: Effects of vegetation type on soil wetting pattern and preferential flow in arid mountainous areas of northwest China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15683, https://doi.org/10.5194/egusphere-egu25-15683, 2025.
Progressive climate change, historical drainage practices, and low precipitation levels in the district of Neustadt a. d. Aisch-Bad Windsheim (Northern Bavaria) necessitate innovative strategies to improve the regional landscape water balance. Within the GrüneGräben+ project, the Ansbach Water Management Authority integrated overflow weirs into existing drainage channels in the study areas Buchholzgraben, Langenwasengraben, and Bodenfeldgraben. These structures are designed to manage floodwaters in a controlled manner while simultaneously promoting infiltration of surface water into the soil. The infiltrated water can either be utilized as plant-available moisture or contribute to stabilizing groundwater levels by percolation.
Each location has been equipped with extensive measurement instrumentation, including rain gauges, surface water sensors, temperature sensors, and soil moisture sensors. In addition, comprehensive field surveys were carried out, where soil samples taken from the immediate vicinity of the channels were analyzed in the laboratory for their soil physical properties. Further measurements included soil moisture assessments via time domain reflectometry (TDR), infiltration tests using double-ring infiltrometers, and topographic data obtained from drone photogrammetry and GPS surveys. These data provide a detailed basis for characterizing runoff and infiltration processes, as well as microtopography, which are used to calibrate and validate hydrological model output.
To evaluate the effectiveness of the measures, hydrological models are employed across multiple spatial scales, primarily using the physically-based numerical models HydroGeoSphere (HGS) and SWAT+. Modeling first takes place at the plot scale (PE), where HGS simulates the interactions between surface water and the porous medium surrounding the trench while factoring macropores, surface crusting, and crop rotation. This complex water flow is represented by the three-dimensional Richards equation in the porous media domain, and the two-dimensional shallow water equation in the surface domain. By using the corresponding Van Genuchten parameters derived from laboratory experimentation, the impact and changes in borders of capillary fringe, field capacity, and wilting point are studied.
Moreover, HGS is also applied at the catchment scale to generate the boundary conditions required by the smaller plot-scale model. At the catchment level, scenarios such as using a series of weirs to improve the water balance on a broader scale are simulated. The SWAT+ model is likewise employed to investigate additional scenarios regarding the effectiveness of these measures across the catchment. The results provide a scalable foundation for transferring the effects of these interventions to larger landscape units, thereby enhancing the region’s resilience to water stress brought on by climate change.
How to cite: El Hajjar, S. and Keßel, N.: From Plot to Catchment: Multi-Scale Modeling of Overflow Weirs to Strengthen Regional Water Resilience in Northern Bavaria, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17573, https://doi.org/10.5194/egusphere-egu25-17573, 2025.
Soil moisture is a cornerstone variable in the interaction between the land and the atmosphere, controlling hydrological and vegetation processes. Soil moisture variations in space and time are a key input for various applications in hydrology, geomorphology, agriculture and soil sciences. The direct monitoring of soil moisture and upscaling to large areas is challenging, while satellite remote sensing is only possible for the top few centimetres of the soil column with considerable uncertainties. In this study, we present a new soil moisture reanalysis for the entire Switzerland, consisting of daily resolution soil moisture maps at six depths (from 0 to 2 m) at a horizontal resolution of 250 m during 2016-2023. The maps are generated as a part of a detailed numerical simulation of the hydrological cycle of Switzerland using the mechanistic eco-hydrological model Tethys-Chloris (T&C).
T&C represents essential components of the hydrological and carbon cycles, resolving exchanges of energy, water, and CO2 between the land surface and the atmosphere. Soil moisture dynamics in saturated and unsaturated soils are solved using the one-dimensional Richards equation for vertical flow and the kinematic wave equation for lateral subsurface flow. The model was forced by hourly meteorological data from the SwissMetNet weather station network and a gridded precipitation product, alongside state-of-the-art land cover and soil characteristics. Results of T&C align well with independent in-situ and remote observations of soil moisture, as well as other eco-hydrological variables such as streamflow, snow depth, LAI, and fluxes of CO2, water and energy which lend credibility to the soil moisture reanalysis.
The study period (2016-2023) includes two recent years of severe spring-summer droughts (2018 and 2022), which are used to showcase how soil moisture anomalies have been developing throughout these dry periods. Preliminary analyses show that during the spring and summer of 2018, which were preceded by a relatively wet winter, soil moisture anomalies were small except in the eastern areas of the Central Plateau where they reached approximately -35% compared to the 2016-2023 seasonal average. In contrast, the spring and summer of 2022, which were preceded by a dry winter, exhibited more widespread anomalies ranging from -15% to -35%, affecting the Jura Mountains, the Central Plateau, and the lower elevations of the Southern Alps. In general, results reveal a large spatial and temporal variability across the six biogeographical regions of Switzerland (Jura Mountains, Central Plateau, Northern Alps, Eastern Alps, Western Alps, and Southern Alps). The soil moisture reanalysis presented in this study is the first of its type, and can be used as a reference dataset and as input for studies looking at floods, landslides, crop productivity, tree water stress, wildfire risk and other applications, where knowledge of soil moisture is essential.
How to cite: Buri, P., Ayala, Á., McCarthy, M., Fatichi, S., Brun, P., Karger, D., Chen, L., and Pellicciotti, F.: High-resolution soil moisture reanalysis of Switzerland (2016-2023), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18836, https://doi.org/10.5194/egusphere-egu25-18836, 2025.
Global warming is particularly pronounced in mountainous alpine regions like the Swiss Alps, with consequences on local to global ecosystems. Within alpine regions, the climatically sensitive treeline ecotone is situated between the timberline, where the forest canopy is connected, and the unvegetated alpine zone. This ecotone is comprised mostly of shrubs and grasses, with smaller trees. The treeline ecotone is thus characterized by marked small-scale spatial variability in landform, rock, soil, and vegetation, making it challenging for generalizing and modelling landscape changes. In this regard, highly resolved spatial and temporal landscape assessment is of utmost importance in assessing the response of such sensitive, yet, dynamic ecotones to global warming.
Here, we investigate how the amount of solar radiation and temporal extent of snow cover influence soil temperature and moisture at two topographical positions: (i) depression and (ii) ridge. We hypothesized that topographical features, as well as soil composition are key factors influencing soil moisture dynamics, and thermal exchange. These two sites were selected within a single landform on a glacially shaped alpine meadow to minimize the effect of other ecosystem factors that were not of interest to this study. Geophysical measurements were used to characterize the subsurface structure of the landform between the two sites. A soil profile up to a depth of 80 cm at the depression and 50 cm at the ridge was opened, described and sampled. Each profile was further equipped with microclimate sensors for in-situ measurements of soil temperature, moisture, and matric potential over a period of one and a half years. The profile soil samples were analyzed for texture, porosity, and organic matter content.
The results indicated that the extent of snow cover shapes the dynamics of soil temperature and moisture. The duration of snow cover was substantially influenced by local topography, as observed in snow persisting for four weeks longer in the depression compared to the ridge during summer. This, in turn, affected soil thermal behavior and contributed to a longer growing season on the ridge than in the depression. Temperature and moisture variability were more pronounced on the ridge, with soil temperature interquartile ranges of 0.2°C to 2.4°C in the depression and 0.3°C to 5.4°C on the ridge, highlighting greater temperature variability on the ridge. Similarly, soil moisture content showed unexpected patterns, with a median of 0.38 m³ m⁻³ in the depression and 0.46 m³ m⁻³ on the ridge. This result contrasts with expectations based on the higher clay and silt content in the depression, which typically promotes moisture retention, and merits further examination.
Our findings highlight the critical influence of snow cover and topography on soil temperature and moisture dynamics within the alpine treeline ecotone. Unexpectedly higher moisture levels on the ridge location and pronounced thermal variability emphasize the need to account for localized soil and microclimatic interactions. These results underscore the challenges in generalizing ecosystem responses to climate change and the importance of small-scale assessments in sensitive alpine landscapes.
How to cite: Diederich, K., Asabere, S. B., Klinge, M., Schwindt, D., Guggenberger, G., and Sauer, D.: Local landscape morphology controls soil temperature and moisture dynamics at an alpine treeline ecotone, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18894, https://doi.org/10.5194/egusphere-egu25-18894, 2025.
Accurate numerical weather prediction (NWP) and climate modelling depend critically on high-fidelity simulation of land surface processes and their interactions with the atmosphere. These interactions are governed by land surface state variables (LSSVs) such as soil moisture, soil temperature, and land surface (skin) temperature, which regulate the energy, water, and carbon fluxes at the land-atmosphere interface. LSSVs strongly influence near-surface atmospheric state variables, including air temperature and relative humidity, which are key to reliable NWP and climate forecasts. To enhance the representation of soil and vegetation processes in land surface models (LSMs), focussing on ECLand in first instance, we are developing a unified hydro-thermal framework for improved coupling of soil moisture and heat transport, and related land-atmosphere coupling. It integrates soil hydraulic and thermal properties, which are typically modelled independently, to improve the simulation of energy and water fluxes. For ECLand, we introduced two key modifications. First, the van Genuchten (1980) soil water retention curve (SWRC) was replaced with a formulation which explicitly accounts for adsorbed and capillary water content (e.g., Lu, 2016). This modification allows for a more physically realistic representation of soil hydraulic properties, particularly under dry conditions. Secondly, the thermal conductivity function of Peters-Lidard et al. (1998), currently used in ECLand, was replaced with an equation which directly links thermal conductivity to the SWRC parameters (Lu & McCartney, 2024), ensuring consistent coupling between soil hydraulic and thermal properties. This new set of equations is being developed to improve the representation of the below-ground part of the skin conductivity, a key parameter for predicting skin temperature, which is critical for accurate energy balance predictions at the land surface, including skin heat flux. While ECLand currently uses a lumped approach, whereby the skin conductivity controls heat flow through topsoil and vegetation combined, the JULES model explicitly separates the contributions of soil and vegetation. We plan to adopt equations from the JULES model for the above-ground part of skin conductivity and integrate them into the updated ECLand model, with the aim to enhance the physical representation of surface heat flux dynamics. The updated model will be tested at multiple sites, including Cabauw, to evaluate its performance. We aim to demonstrate significant improvements in the simulation of soil moisture, soil temperature, and energy fluxes, showcasing the potential of this new framework. However, broader validation across a range of climatic and soil conditions will be required to ensure robustness and scalability. Future work will focus on developing a global soil hydro-thermal parameter set tailored to the new equations, enabling global application of the framework in the IFS. Once thoroughly tested and calibrated, this advancement is expected to improve the predictability of both land surface and atmospheric state variables, ultimately enhancing the reliability of ECMWF’s seasonal to sub-seasonal forecasts.
How to cite: Kandala, R., Verhoef, A., Boussetta, S., Rosnay, P. D., Zeng, Y., and Black, E.: A unified hydro-thermal framework for improved skin conductivity and skin temperature in the ECLand model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16289, https://doi.org/10.5194/egusphere-egu25-16289, 2025.
Soil structure is nearly as important as soil texture in determining the soil hydraulic properties at the core scale. Soil structure was also shown to significantly affect runoff and drainage at ecosystem scale (Fatichi et al., 2020; Bonetti et al., 2021). However, its effect on vadose zone hydrology at 100 km scale — at which climate and land surface models are often run — remains unclear. Seminal works (Fatichi et al., 2020; Bonetti et al., 2021) found a small effect of soil structure at these large scales, but this has been linked to the nature of the subgrid parametrization of precipitation (or of soil hydraulic conductivity) in the employed models. Here, we evaluate the effect of soil structure on vadose zone hydrology in the ORCHIDEE land surface model, which models infiltration using a unique subgrid parametrization of soil hydraulic conductivity (Vereecken et al., 2019). In ORCHIDEE, we find a larger effect of soil structure on the water cycle than reported for OLAM (Fatichi et al., 2020). We link this to the subgrid variability of hydraulic conductivity in ORCHIDEE, which ensures that the structural modifications of soil hydraulic properties are activated at all rainfall rates. Finally, we discuss the perspectives for parametrizing the structural modifications of soil hydraulic properties at large scales using soil moisture observations.
Bonetti, S., Wei, Z., & Or, D. (2021). A framework for quantifying hydrologic effects of soil structure across scales. Communications Earth & Environment, 2 (1), 1–10. https://doi.org/10.1038/s43247-021-00180-0
Fatichi, S., Or, D., Walko, R., Vereecken, H., Young, M. H., Ghezzehei, T. A., Hengl, T., Kollet, S., Agam, N., & Avissar, R. (2020). Soil structure is an important omission in Earth System Models. Nature Communications, 11 (1), 522. https://doi.org/10.1038/s41467-020-14411-z
Vereecken, H., Weihermüller, L., Assouline, S., Šimůnek, J., Verhoef, A., Herbst, M., Archer, N., Mohanty, B., Montzka, C., Vanderborght, J., Balsamo, G., Bechtold, M., Boone, A., Chadburn, S., Cuntz, M., Decharme, B., Ducharne, A., Ek, M., Garrigues, S., … Xue, Y. (2019). Infiltration from the Pedon to Global Grid Scales: An Overview and Outlook for Land Surface Modeling. Vadose Zone Journal, 18 (1), 180191. https://doi.org/10.2136/vzj2018.10.0191
How to cite: Kiałka, F., Flores, O., Naudts, K., Luyssaert, S., and Guenet, B.: Effect of soil structure on vadose zone hydrology in the ORCHIDEE land surface model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19175, https://doi.org/10.5194/egusphere-egu25-19175, 2025.
Modeling soil hydraulic processes requires robust and stable numerical solutions, also when computational resources are limited. Different challenging problems like sudden changes of pressure or fluxes at the boundary of the model domain or very dry initial conditions are challenges for standard numerical solution methods such low-order finite difference and finite element methods. The Method of Lines approach is proven to achieve numerical robustness and stability while allowing the handling of different complex soil hydraulic models for one-dimensional problems. To be applicable in a wide range of scenarios the method should also be easily extensible. Here the Method Of Lines approach is shown to enable the handling of different complex soil hydraulic models, the modification of Richards' equation to consider non-equilibrium effects and the extension with a lateral flow model to form a combined 1.5D hillslope model.
A slightly modified Method of Lines approach is used to solve the pressure based 1D Richards' equation. A finite differencing scheme is applied to the spatial derivative and the resulting system of ordinary differential equations is reformulated as differential-algebraic system of equations. The open-source code IDAS from the Sundials suite is used to solve the DAE system. To show the broad applicability of the method, several successful use cases are presented. These range from the inclusion of more complex soil hydraulic models to be able to consider hystersis effects and dual-permeability flow over the extension of Richards' equation to model non-equilibrium unsaturated flow to linking the Richards' equation with the Boussinesq lateral flow equation to form an efficient 1.5-D hillslope model.
The results show that the Method of Lines approach for solving Richards' equation satisfies the required conditions of numerical robustness and stability and allows for easily including new processes and a wider set of applications.
How to cite: Mietrach, R., Schütze, N., and Wöhling, T.: A robust solution to Richards' equation with use cases in complex soil hydraulic models, non-equilibrium unsaturated flow in soil and model coupling using the Method Of Lines, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19458, https://doi.org/10.5194/egusphere-egu25-19458, 2025.
Posters virtual: Mon, 28 Apr, 14:00–15:45 | vPoster spot A
EGU25-15178 | ECS | Posters virtual | VPS8
Evaluating a rapid approach for estimating soil hydraulic conductivity function from near-surface infiltration measurementsMon, 28 Apr, 14:00–15:45 (CEST) | vPA.18
Accurate estimation of the soil hydraulic conductivity function (SHCF), which describes the relationship between hydraulic conductivity and matric suction in soil, is essential for modeling flow and transport processes in the vadose zone. Traditional steady-state methods for directly determining SHCF are often laborious, time-consuming, and sometimes inadequate for capturing transient-state flow conditions. This study aims to propose a simple, quick, and accurate method for estimating SHCF that facilitates transient-state flow analysis during vadose zone modeling. The proposed method involves inverse numerical modeling using cumulative infiltration and final moisture content data from surface infiltration tests conducted with a handy mini disc infiltrometer (MDI). To validate this approach, the MDI-inverse modeling results were compared with SHCF results from another transient-state method, the instantaneous profile method (IPM), under similar initial soil conditions. The MDI infiltration tests were performed in homogeneously packed soil columns for two soils (identified as loam and silty clay loam textures) collected from nearby field sites. For each soil, separate IPM tests were conducted in soil columns equipped with soil moisture and matric suction sensors at various depths to facilitate calculation of reference SHCF. A comparison between the MDI and reference IPM results revealed a good agreement, with a low normalized RMSE (under 15%) for the estimated SHCFs and a low relative error (under 35%) for the optimized van Genuchten parameters α and n. The findings indicate that MDI-based cumulative infiltration measurements can reliably estimate SHCF via inverse simulation, providing a practical solution for field applications where traditional sensor deployment is challenging. Moreover, the results also establish MDI as a rapid, convenient, and non-invasive tool for determining SHCF for transient-state flow scenarios.
How to cite: Naik, A. P. and Pekkat, S.: Evaluating a rapid approach for estimating soil hydraulic conductivity function from near-surface infiltration measurements , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15178, https://doi.org/10.5194/egusphere-egu25-15178, 2025.
