A Modular Framework for Modeling Unsaturated Soil Hydraulic Properties Over the Full Moisture Range

Weber, Tobias K. D.; Durner, Wolfgang; Streck, Thilo; Diamantopoulos, Efstathios

doi:10.1029/2018wr024584

Cited by 41 publications

(71 citation statements)

References 134 publications

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“…Despite the convenience of the assumption in applications, it is widely accepted that residual water exists in the form of water film adsorbed on the particle surface and is mobile. When the adsorptive water retention is considered, the water content can be written as (Weber et al, 2019)…”

Section: Model Descriptionmentioning

confidence: 99%

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An empirical soil water retention model based on probability laws for pore‐size distribution

Zheng

Shen

Wang

et al. 2020

Vadose Zone Journal

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Knowledge of the soil water retention curve (SWRC) is critical to mathematical modeling of soil water dynamics in the vadose zone. Traditional SWRC models were developed based on bundles of cylindrical capillaries (BCCs) using a residual water content, which fail to accurately describe the dry end of the curve. This study improved and expanded on the traditional BCC models. Specifically, the total water retention was treated as a weighed superposition of capillary and adsorptive components. We proposed a mathematical continuous expression for water retention from saturation to oven dryness, which also allowed for a partition of capillary and adsorptive retention. We further evaluated six capillary retention functions using different probability laws for pore-size distributionnamely, the log-logistic, Weibull, lognormal, two-parameter van Genuchten (VG), three-parameter VG (or Dagum), and Fredlund-Xing (FX) distributions. Model testing against 144 experimental data showed better agreement of the proposed model with experimental observations than the traditional approaches that use the residual water content. The Dagum and FX distributions, which have one more degree of freedom, provided better agreement with experimental data than the other four distributions. The log-logistic and lognormal distributions fitted the experimental data better than the Weibull and VG distribution for loam soils. In addition, the fitted weighting factor w using the log-logistic and lognormal distributions better correlated to soil clay content than the other four distributions. Our study suggests that the log-logistic and lognormal distributions are more suitable to model soils' pore-size distribution than other tested distributions.

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Section: Model Descriptionmentioning

confidence: 99%

“…The new model allows a partition of capillary and film components and is continuous over saturation to oven dryness. It does not introduce any additional parameters compared with Equations 2 or 3, incorporating Equation 6 by Peters (2013) or Equation 7 by Weber et al (2019).…”

Section: Adsorptive Water Retention Function S Filmmentioning

confidence: 99%

An empirical soil water retention model based on probability laws for pore‐size distribution

Zheng

Shen

Wang

et al. 2020

Vadose Zone Journal

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“…The CV of s is remarkably homogeneous in space (Figure 4d), with the exception of a few areas characterized by sandy soils, which tend to drain quickly and have smaller soil water storage capacity (difference between s at saturation and field capacity) and therefore have a shorter memory timescale, which may contribute to the higher variability. However, Weber, Durner, Streck, and Diamantopoulos (2019) argue that the Clapp and Hornberger (1978) parameterization for soil hydraulic properties used in LIS and several other land surface models is outdated, and newer, perhaps more accurate approaches to soil water storage modeling are currently being worked on but are not available at the time of this study. At the spatial resolution we examine here (i.e., 4-km grid resolution), and in regional studies in general, local variations in soil properties and LULC are averaged out, which inherently reduces CV.…”

Section: F I G U R Ementioning

confidence: 99%

Drivers of regional soil water storage memory and persistence

Jacobs

Bertassello

Rao

2020

Vadose Zone Journal

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Soil water storage dynamics link landscape and climate processes with consequent impacts on hydrologic and biogeochemical cycles, and on ecosystem functions. We explore regional-scale, spatiotemporal dynamics of root-zone soil water storage using spatially explicit, long-term simulations from a land data assimilation system over an area of ∼2 million km 2 in the U.S. Midwest. We synthesize the dataset to examine spatial patterns of hydroclimatic forcing and soil and vegetation properties to identify the key drivers of soil water storage across the region. To identify differences in temporal hydrologic variability between sites with different soil and vegetation characteristics, we focus on daily data from 10 locations, representative of three major land cover types in the region. We use the concepts of (a) soil water memory to evaluate differences in landscape buffering of rainfall and (b) persistence to evaluate the threshold-crossing properties of statistically defined "wet" and "dry" soil water conditions. Power spectral analyses of soil water storage reveal that regionally consistent patterns emerge in memory at multiple temporal scales. Threshold-crossing analyses reveal corresponding similarity in persistence between sites. The analyses show that stochastic rainfall is the key driver of landscape hydrologic dynamics, with rainfall frequency as the primary determinant of persistence across the region, whereas differences in land cover and soil properties across the region have second-order influence. The synthesis approach we present here is useful for ecological and agricultural risk assessments of climate change impacts, including increasing frequency of extreme events such as droughts and floods, but primarily points to the need for better understanding of future precipitation changes.

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“…However, a number of well-known shortcomings are summarized by Weber et al (2019), motivating the authors to present a model framework. In the Weber et al (2019) model, termed Brunswick (BW) model, the soil water retention curve (WRC) and the hydraulic conductivity curve (HCC) are ramified into a capillary and noncapillary pore space. This is achieved by introducing only one additional model parameter.…”

Section: Introductionmentioning

confidence: 99%

“…Some selected studies exist for other models, too (van Looy et al, 2017). Again, it has been demonstrated numerous times that VGM and VGM-type parameterizations of the SHP suffer from well-known problems (Peters, 2013;Weber et al, 2019). However, no readily available hyPTF predicting parameters of more physically comprehensive models such as the BW model exist.…”

Section: Introductionmentioning

confidence: 99%

Pedotransfer Function for the Brunswick Soil Hydraulic Property Model and Comparison to the van Genuchten‐Mualem Model

Weber

Finkel

Gonçalves

et al. 2020

Water Resources Research

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Modeling soil hydraulic properties requires an effective representation of capillary and noncapillary storage and conductivity. This is made possible by using physically comprehensive yet flexible soil hydraulic property models. Such a model (Brunswick [BW] model) was introduced by Weber et al. (2019, https://doi.org/10.1029/2018WR024584), and it overcomes some core deficiencies present in the widely used van Genuchten-Mualem (VGM) model. We first compared the performance of the BW model to that of the VGM model in its ability to describe water retention and hydraulic conductivity data on a set of measurements of 402 soil samples with textures covering the entire range of classes. Second, we developed a simple transfer function to predict BW parameters based on VGM parameters. Combined with our new function, any existing pedotransfer function for the prediction of the VGM parameters can be extended to predict BW model parameters. Based on information criteria, the smaller variance of the residuals, and a 40% reduction in mean absolute error in the hydraulic conductivity over all samples, the BW model clearly outperforms VGM. This is possible as the BW model explicitly accounts for hydraulic properties of dry soils. With the new pedotransfer function developed in this study, better descriptions of water retention and hydraulic conductivities are possible. We are convinced that this will strengthen the utility of the new model and enable improved field-scale simulations, climate change impact assessments on water, energy and nutrient fluxes, as well as crop productivity in agroecosystems by soil-crop and land-surface modeling. The models and the pedotransfer function are included in an R package spsh (https://cran.r-project.org/package¼spsh). Plain Language Summary Soil hydraulic property models are mathematical functions, which describe the relationship between the soil water pressure head and the state of soil water saturation, on the one hand, and the soil water pressure head and the unsaturated soil hydraulic conductivity, on the other. These types of mathematical functions are flexible by adjustable parameters. With one set of model equations, the hydraulic properties of soils which may have very different properties due to their vast natural variability can be described. The models treated in this work are (i) the van Genuchten-Mualem model, a model with well-known problems, but still frequently applied, and (ii) a relatively new physical comprehensive model, named the Brunswick model. First of all, in a data-based comparison of model performance, we demonstrate that the Brunswick model has systematic advantages. Second, knowledge about these above-mentioned parameters can be determined through other mathematical functions, so-called hydro-pedotransfer functions, which empirically relate these parameters to observed soil properties. The information about these soil properties can be measured in the laboratory and is also recorded in soil maps. We created a new pedotransfer function to facilitate the predictio...

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A Modular Framework for Modeling Unsaturated Soil Hydraulic Properties Over the Full Moisture Range

Cited by 41 publications

References 134 publications

An empirical soil water retention model based on probability laws for pore‐size distribution

An empirical soil water retention model based on probability laws for pore‐size distribution

Drivers of regional soil water storage memory and persistence

Pedotransfer Function for the Brunswick Soil Hydraulic Property Model and Comparison to the van Genuchten‐Mualem Model

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