Jul 2026· Soil Science Society of America Journal· 0 citations· 30 references
Abstract
The distribution of soil moisture, resulting from the movement of infiltrated water, plays a fundamental role in the hydrological dynamics of hillslopes and in the triggering of landslides. Although water flow in soils occurs in multiple directions due to combined vertical and lateral fluxes, one‐dimensional (1D) flow models are widely adopted as a simplifying assumption in slope‐scale studies, frequently without explicit verification of their validity by researchers. This study evaluates the applicability of the one‐dimensional flow hypothesis under different hydrological conditions and over time. Soil moisture dynamics were simulated using the Hydrus‐1D model, driven by observed precipitation data and calibrated and validated against in situ soil moisture measurements collected at different depths. The results suggest that, at temporal scales associated with rainfall events capable of triggering landslides, one‐dimensional modelling can adequately to represent soil moisture dynamics in slope environments when coupled with measured soil moisture data for the calibration of hydraulic parameters. In contrast, simulations using soil hydraulic parameters estimated from pedotransfer functions showed limited ability to represent the hydraulic behavior of the soils.
The soil water characteristic curve (SWCC) can quantitatively characterize and predict the retention, movement, and exploitability of soil water in drylands. It holds key scientific significance for optimizing water management, guiding agricultural production, and promoting ecological restoration. In the present research, soil specimens were collected from apricot (
Prunus armeniaca
L.) groves in the hilly regions of southern Ningxia to examine how varying ages of apricot trees influence the SWCC. The accuracy and variability of SWCC measurements in apricot orchards of different ages were assessed using the one‐dimensional horizontal infiltration method. Additionally, unsaturated hydraulic conductivity (
K
θ
), unsaturated diffusion coefficient (
D
), and related hydrological parameters were estimated. The feasibility and accuracy of the one‐dimensional horizontal infiltration method were evaluated using the in situ continuous evaporation method with a tensiometer. The results indicated that, compared with CK (farmland corn field), it took 78.89% longer for the wetting front to reach a depth of 40.0 cm in the 35‐year‐old stand, and sorptivity (
S
) decreased by 36.36%. A comparative analysis of the low matric potential range SWCC, obtained using both the one‐dimensional horizontal infiltration technique and the tensiometer technique, revealed that the
R
2
value was greater than 0.765, while the root mean square error (RMSE) and mean absolute error (MAE) were both less than 0.1 cm
3
/cm
3
. This demonstrates that the one‐dimensional horizontal infiltration method has high precision in measuring the SWCC of forest soil. A comparison of the estimation results from two SWCC models, namely, the van Genuchten model as well as the Brooks–Corey model, showed that the van Genuchten model had a higher
R
2
value and lower RMSE and MAE compared to the Brooks–Corey model. This indicates that the van Genuchten model is more effective at predicting the SWCC of forest soil. Under the same moisture content conditions, both the
K
θ
and the
D
diminished as stand age increased. The study concluded that hydraulic permeability progressively waned with the escalation of forest age. It also substantiated that the one‐dimensional horizontal infiltration technique is an expeditious and dependable means for gauging the SWCC and pivotal hydrodynamic parameters of forest soil in arid zones.
Gang Wang, Youqi Wang, Changyu Gu et al.· Soil Science Society of Amer...· 0 citations
Abstract. Soil freezing is a major cold region process that influences hydrological response of northern catchments, in particular during winter rainfall and snowmelt events. In land surface models, frozen soil infiltration is difficult to represent because soil structure and hydropedological processes vary at scales finer than the model grid. This is particularly true in operational modeling, where physical process integration must balance performance improvements against computational efficiency and complexity. In this study, we propose a new configuration of the Soil, Vegetation, and Snow (SVS) model used within the operational prediction systems of Environment and Climate Change Canada (ECCC) that enhances frozen soil infiltration by reducing both surface runoff and sub-surface lateral flow. We assessed the effects of this new configuration (Fr-Inf) on streamflow simulations at more than 580 hydrometric stations located in the Great-Lakes and Saint-Lawrence domain over a five-year period. Fr-Inf significantly improves the Kling-Gupta Efficiency (KGE) compared to the default soil freezing configuration (Fr; ΔKGE = 0.28) but slightly underperforms the configuration of SVS without frozen soil (noFr; ΔKGE = −0.07). Strong degradations relative to the no freezing configuration (ΔKGE < −0.5) are observed only at 4 stations with Fr-Inf (< 1 %) as opposed to 172 stations under the Fr configuration (33 %), highlighting the robustness of the approach. To ensure that the proposed change is also acceptable in the context of operational numerical weather prediction, an evaluation of its impact on soil freezing depth as well as screen-level temperature and dew point temperature predictions is performed against in-situ observations. These results support the potential operational implementation of soil freezing at ECCC for numerical weather and streamflow prediction.
B. Bouchard, Vincent Vionnet, É. Gaborit et al.· Hydrology and Earth System S...· 0 citations
(English) The top layer of soil on a slope is highly dynamic, influenced by atmospheric forces and the presence of vegetation. The vegetation condition plays a crucial role in determining the amount of water transpiration and evaporation from the slope surface, thus affecting slope performance by altering temperature, water content, and pore water pressure within the soil mass. Many numerical models often neglect the vegetation impact on soil performance. To capture these effects, this study employs a finite element model in CODE_BRIGHT that integrates vegetation and climate-driven interactions, aiming to bridge the gap between reality and simulation. A specialized boundary condition is developed to simulate soil–vegetation–atmosphere (SVA) processes with hydraulic hysteresis, linking canopy resistance to solar radiation, vapor pressure deficit, and soil saturation. Model validation using three years of field data from the Agropolis slope in Barcelona shows strong agreement, confirming its ability to reproduce vegetation effects on slope hydrothermal behavior. Results reveal pronounced daily temperature variations in the root zone, higher temperatures on south-facing slopes, and stronger drying under vegetation during hot, dry periods.
Parametric analysis identifies leaf area index (LAI), root density, and vegetation fraction as key factors influencing soil moisture. Root density and LAI most strongly affect water retention, dense roots lower summer saturation by up to 40%, while high LAI reduces surface drying by 30%. Vegetation fraction enhances winter storage but intensifies summer drying.
To better represent unsaturated soils, a hysteretic soil–water retention model is implemented in CODE_BRIGHT, coupling suction and void ratio changes to improve accuracy in scenarios such as rainfall-induced landslides.
Finally, an enhanced Barcelona Basic Model (BBM-VEG) is formulated within a thermo-hydro-mechanical (THM) framework. The model introduces a strain-dependent reinforcement factor (Rpveg), correlated with root mass fraction and activation strain, allowing soil stiffness and strength to evolve dynamically. Validated with triaxial and tensile tests, it accurately captures the mechanical response of rooted soils. Slope simulations under hydraulic (infiltration rates of 0.001–0.003 and 0.0005 kg/s) and thermal (15–60 °C) cycles show that vegetation limits infiltration, enhances evapotranspiration, expands the unsaturated zone, and reduces deformation by up to 70% compared to bare slopes.
(Català) La capa superior del sòl en un talús és altament dinàmica, influïda per les forces atmosfèriques i la presència de vegetació. L’estat de la vegetació té un paper crucial en la determinació de la quantitat de transpiració i evaporació d’aigua des de la superfície del talús, afectant així el seu comportament mitjançant l’alteració de la temperatura, el contingut d’aigua i la pressió intersticial dins de la massa de sòl. Molts models numèrics sovint descuiden l’impacte de la vegetació en el comportament del sòl. Per capturar aquests efectes, aquest estudi utilitza un model d’elements finits a CODE_BRIGHT que integra les interaccions impulsades per la vegetació i el clima, amb l’objectiu de reduir la bretxa entre la realitat i la simulació. Es desenvolupa una condició de contorn especialitzada per simular els processos sòl–vegetació–atmosfera (SVA) amb histèresi hidràulica, vinculant la resistència del dosser amb la radiació solar, el dèficit de pressió de vapor i la saturació del sòl. La validació del model amb tres anys de dades de camp del talús d’Agropolis a Barcelona mostra una forta concordança, confirmant la seva capacitat per reproduir els efectes de la vegetació en el comportament hidrotermal del talús. Els resultats revelen variacions diàries pronunciades de temperatura a la zona radicular, temperatures més elevades als talussos orientats al sud i un assecat més intens sota vegetació durant períodes càlids i secs.
L’anàlisi paramètrica identifica l’índex d’àrea foliar (LAI), la densitat radicular i la fracció de vegetació com a factors clau que influeixen en la humitat del sòl. La densitat radicular i el LAI afecten amb més intensitat la retenció d’aigua: arrels denses poden reduir la saturació estival fins a un 40%, mentre que un LAI elevat disminueix l’assecat superficial en un 30%. La fracció de vegetació millora l’emmagatzematge hivernal, però intensifica l’assecat estival.
Per representar millor els sòls no saturats, s’implementa a CODE_BRIGHT un model histèric de retenció sòl–aigua que acobla la succió i els canvis en el volum de buits per millorar la precisió en escenaris com ara esllavissades induïdes per la pluja.
Finalment, es formula un Model Bàsic de Barcelona millorat (BBM-VEG) dins d’un marc termo-hidro-mecànic (THM). El model introdueix un factor de reforç dependent de la deformació (Rpveg), correlacionat amb la fracció de massa radicular i la deformació d’activació, permetent que la rigidesa i la resistència del sòl evolucionin dinàmicament. Validat mitjançant assaigs triaxials i de tracció, el model captura amb precisió la resposta mecànica dels sòls amb arrels. Les simulacions de talussos sota cicles hidràulics (taxes d’infiltració de 0,001–0,003 i 0,0005 kg/s) i tèrmics (15–60 °C) mostren que la vegetació limita la infiltració, potencia l’evapotranspiració, amplia la zona no saturada i redueix la deformació fins a un 70% en comparació amb talussos nus.
(Español) La capa superior del suelo en una ladera es altamente dinámica y está influenciada por las fuerzas atmosféricas y la presencia de vegetación. El estado de la vegetación desempeña un papel crucial en la determinación de la cantidad de agua transpirada y evaporada desde la superficie de la ladera, afectando así su comportamiento al modificar la temperatura, el contenido de agua y la presión de poros dentro de la masa del suelo. Muchos modelos numéricos suelen pasar por alto el impacto de la vegetación en el desempeño del suelo. Para capturar estos efectos, este estudio emplea un modelo de elementos finitos en CODE_BRIGHT que integra las interacciones impulsadas por la vegetación y el clima, con el objetivo de reducir la brecha entre la realidad y la simulación. Se desarrolla una condición de contorno especializada para simular los procesos suelo–vegetación–atmósfera (SVA) con histéresis hidráulica, vinculando la resistencia del dosel a la radiación solar, el déficit de presión de vapor y la saturación del suelo.
La validación del modelo con tres años de datos de campo del talud de Agropolis en Barcelona muestra una fuerte concordancia, confirmando su capacidad para reproducir los efectos de la vegetación en el comportamiento hidrotermal de la ladera. Los resultados revelan variaciones diarias pronunciadas de temperatura en la zona radicular, temperaturas más altas en laderas orientadas al sur y una mayor desecación bajo vegetación durante periodos cálidos y secos.
El análisis paramétrico identifica el índice de área foliar (LAI), la densidad radicular y la fracción de vegetación como los principales factores que influyen en la humedad del suelo. La densidad de raíces y el LAI afectan más intensamente la retención de agua: las raíces densas reducen la saturación estival hasta en un 40%, mientras que un LAI elevado disminuye la desecación superficial en un 30%. La fracción de vegetación aumenta el almacenamiento invernal, pero intensifica la desecación durante el verano.
Para representar mejor los suelos no saturados, se implementa en CODE_BRIGHT un modelo histerético de retención agua–suelo, acoplando los cambios de succión y relación de vacíos para mejorar la precisión en escenarios como los deslizamientos inducidos por lluvia.
Finalmente, se formula un Modelo Básico de Barcelona mejorado (BBM-VEG) dentro de un marco termo-hidro-mecánico (THM). El modelo introduce un factor de refuerzo dependiente de la deformación (Rpveg), correlacionado con la fracción de masa radicular y la deformación de activación, lo que permite que la rigidez y la resistencia del suelo evolucionen dinámicamente. Validado con ensayos triaxiales y de tracción, el modelo reproduce con precisión la respuesta mecánica de los suelos con raíces. Las simulaciones de laderas bajo ciclos hidráulicos (tasas de infiltración de 0.001–0.003 y 0.0005 kg/s) y térmicos (15–60 °C) muestran que la vegetación limita la infiltración, mejora la evapotranspiración, amplía la zona no saturada y reduce la deformación hasta en un 70% en comparación con laderas desnudas.
In Earth system models, three‐dimensional prognostic subsurface hydrodynamics, including groundwater flow, are currently missing at the global scale. In order to prepare Earth system models for kilometer‐scale simulations with integrated continental hydrology, the ParFlow hydrological model has been coupled to the land model of the ICON modeling framework. Global simulations of atmosphere and land were conducted with a two‐way coupling between ParFlow and the soil hydrological scheme of ICON‐Land over the pan‐European region. In this first implementation, ParFlow and ICON‐Land exchange surface moisture fluxes and soil water. The extended summer months of five consecutive years were simulated with 20 km horizontal grid spacing. The explicit treatment of surface and subsurface water in ParFlow has multiple effects. Some notable impacts are presented related to soil moisture variability and lateral redistribution of moisture. Correlations with surface latent heat flux and precipitation show regionally stronger land‐atmosphere coupling. This affects the seasonal change in soil water content in Central Europe during the summer. In addition, the lateral flow of near‐surface groundwater, which is intrinsically linked to the formation of river networks, is shown to influence the evolution of the atmosphere.
Jan Weinkaemmerer, R. Schnur, Klaus Goergen et al.· Journal of Advances in Model...· 0 citations
Soil hydraulic properties govern the movement and storage of water in soils and are essential inputs for hydrological and land surface models, influencing water‐holding capacity, matter and energy transport, erosion susceptibility and plant water availability. However, direct measurement of these properties is labour‐intensive and thus often limited in spatial coverage. Therefore, pedotransfer functions (PTFs) are widely used to estimate soil hydraulic properties from readily available soil characteristics. We present a spatial dataset of soil hydraulic properties for Europe at 0–20 cm depth, developed using harmonised soil property maps derived from the LUCAS dataset and the improved PTFs (EUPTFv2) proposed by Szabó et al., which are developed on the European Hydropedological Data Inventory. The derived dataset includes water content at saturation, field capacity (at −10 and −33 kPa), wilting point (−1500 kPa), saturated hydraulic conductivity and their associated uncertainty maps. In addition, we derived available water capacity and air capacity (air‐filled porosity) from the predicted properties. The input datasets (LUCAS‐based soil maps) used in this study are derived from harmonised data in terms of measurement methods and spatial consistency. This is expected to improve the reliability of the resulting maps compared with existing products. The generated dataset is freely available and can therefore support a wide range of environmental and modelling applications.
Surya Gupta, C. Alewell, C. Ballabio et al.· Hydrological Processes· 0 citations
Soil moisture is a key indicator of agricultural and hydrological drought, but its meteorological controls vary across temporal scales. Using ESA CCI soil moisture products from 2010 to 2022, this study investigated soil moisture variability in the Yangtze River Basin at weekly, monthly, and annual scales. The product was first validated using ground observations and ERA5 reanalysis data, and a generalized additive model (GAM) was then applied to quantify the relative contributions of precipitation, temperature, wind speed, and VPD under normal conditions and during three extreme drought events. The validation showed that ESA CCI soil moisture captured basin-scale variations well, with mean absolute deviations of 0.0460, 0.0434, and 0.0072 m3/m3 in the upper, middle, and lower reaches, respectively, and a basin-wide RMSE of 0.0127 m3/m3 against ERA5. The attribution results revealed a clear scale-dependent shift in soil moisture controls. At the weekly scale, VPD dominated soil moisture variability, with a basin-wide average contribution of 47.04% and a maximum contribution of 55.92% in the lower reaches, indicating that short-term soil drying is mainly driven by VPD. At the monthly scale, precipitation became the primary control, with a basin-wide average contribution of 36.62% and a maximum contribution of 44.65% in the upper reaches, reflecting the role of accumulated rainfall recharge in maintaining soil moisture storage. During extreme drought events, the monthly-scale dominance of precipitation weakened, and precipitation, VPD, temperature, and wind speed each contributed approximately 20–30%, suggesting that drought development results from the combined effects of reduced water input and enhanced atmospheric water loss. These findings indicate that precipitation-based drought monitoring may underestimate rapid soil drying risks, whereas incorporating atmospheric demand indicators such as VPD can improve drought early warning and water resource management under a warming climate.
Yucheng Liu, Ran Huo, Bowen Zhu et al.· Atmosphere· 0 citations