scholarly journals Bayesian inverse modelling of in situ soil water dynamics: using prior information about the soil hydraulic properties

2011 ◽  
Vol 8 (1) ◽  
pp. 2019-2063 ◽  
Author(s):  
B. Scharnagl ◽  
J. A. Vrugt ◽  
H. Vereecken ◽  
M. Herbst
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Vadose Zone ◽  
Hydraulic Properties ◽  
Prior Information ◽  
Hydraulic Parameters ◽  
Soil Hydraulic Properties ◽  
Soil Hydraulic Parameters ◽  
Soil Hydraulic

Abstract. In situ observations of soil water state variables under natural boundary conditions are often used to estimate field-scale soil hydraulic properties. However, many contributions to the soil hydrological literature have demonstrated that the information content of such data is insufficient to reliably estimate all the soil hydraulic parameters. In this case study, we tested whether prior information about the soil hydraulic properties could help improve the identifiability of the van Genuchten-Mualem (VGM) parameters. Three different prior distributions with increasing complexity were formulated using the ROSETTA pedotransfer function (PTF) with input data that constitutes basic soil information and is readily available in most vadose zone studies. The inverse problem was posed in a formal Bayesian framework and solved using Markov chain Monte Carlo (MCMC) simulation with the DiffeRential Evolution Adaptive Metropolis (DREAM) algorithm. Synthetic and real-world soil water content data were used to illustrate our approach. The results of this study corroborate and explicate findings previously reported in the literature. Indeed, soil water content data alone contained insufficient information to reasonably constrain all VGM parameters. The identifiability of these soil hydraulic parameters was substantially improved when an informative prior distribution was used with detailed knowledge of the correlation structure among the respective VGM parameters. A biased prior did not distort the results, which inspires confidence in the robustness and effectiveness of the presented method. The Bayesian framework presented in this study can be applied to a wide range of vadose zone studies and provides a blueprint for the use of prior information in inverse modelling of soil hydraulic properties at various spatial scales.

scholarly journals Inverse modelling of in situ soil water dynamics: investigating the effect of different prior distributions of the soil hydraulic parameters

2011 ◽  
Vol 15 (10) ◽  
pp. 3043-3059 ◽  
Author(s):  
B. Scharnagl ◽  
J. A. Vrugt ◽  
H. Vereecken ◽  
M. Herbst
Keyword(s):  
Soil Water ◽  
Prior Information ◽  
Water Dynamics ◽  
Hydraulic Parameters ◽  
Natural Boundary ◽  
Soil Water Dynamics ◽  
Soil Hydraulic Parameters ◽  
Soil Hydraulic ◽  
Natural Boundary Conditions

Abstract. In situ observations of soil water state variables under natural boundary conditions are often used to estimate the soil hydraulic properties. However, many contributions to the soil hydrological literature have demonstrated that the information content of such data is insufficient to accurately and precisely estimate all the soil hydraulic parameters. In this case study, we explored to which degree prior information about the soil hydraulic parameters can help improve parameter identifiability in inverse modelling of in situ soil water dynamics under natural boundary conditions. We used percentages of sand, silt, and clay as input variables to the ROSETTA pedotransfer function that predicts the parameters in the van Genuchten-Mualem (VGM) model of the soil hydraulic functions. To derive additional information about the correlation structure of the predicted parameters, which is not readily provided by ROSETTA, we employed a Monte Carlo approach. We formulated three prior distributions that incorporate to different extents the prior information about the VGM parameters derived with ROSETTA. The inverse problem was posed in a formal Bayesian framework and solved using Markov chain Monte Carlo (MCMC) simulation with the DiffeRential Evolution Adaptive Metropolis (DREAM) algorithm. Synthetic and real-world soil water content data were used to illustrate the approach. The results of this study demonstrated that prior information about the soil hydraulic parameters significantly improved parameter identifiability and that this approach was effective and robust, even in case of biased prior information. To be effective and robust, however, it was essential to use a prior distribution that incorporates information about parameter correlation.

Root effects on soil water and hydraulic properties

Biologia ◽  
2007 ◽  
Vol 62 (5) ◽  
Author(s):  
Horst Gerke ◽  
Rolf Kuchenbuch
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Water Content ◽  
Bulk Density ◽  
Soil Water ◽  
Soil Water Content ◽  
Hydraulic Properties ◽  
Soil Hydraulic Properties ◽  
Soil Hydraulic ◽  
Root Effects

AbstractPlants can affect soil moisture and the soil hydraulic properties both directly by root water uptake and indirectly by modifying the soil structure. Furthermore, water in plant roots is mostly neglected when studying soil hydraulic properties. In this contribution, we analyze effects of the moisture content inside roots as compared to bulk soil moisture contents and speculate on implications of non-capillary-bound root water for determination of soil moisture and calibration of soil hydraulic properties.In a field crop of maize (Zea mays) of 75 cm row spacing, we sampled the total soil volumes of 0.7 m × 0.4 m and 0.3 m deep plots at the time of tasseling. For each of the 84 soil cubes of 10 cm edge length, root mass and length as well as moisture content and soil bulk density were determined. Roots were separated in 3 size classes for which a mean root porosity of 0.82 was obtained from the relation between root dry mass density and root bulk density using pycnometers. The spatially distributed fractions of root water contents were compared with those of the water in capillary pores of the soil matrix.Water inside roots was mostly below 2–5% of total soil water content; however, locally near the plant rows it was up to 20%. The results suggest that soil moisture in roots should be separately considered. Upon drying, the relation between the soil and root water may change towards water remaining in roots. Relations depend especially on soil water retention properties, growth stages, and root distributions. Gravimetric soil water content measurement could be misleading and TDR probes providing an integrated signal are difficult to interpret. Root effects should be more intensively studied for improved field soil water balance calculations.

Soil Properties and Water Movement

1999 ◽  
Author(s):  
J.-Y. Parlance ◽  
T. S. Steenhuis
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Hydraulic Properties ◽  
Volumetric Water Content ◽  
Richards Equation ◽  
Field Scale ◽  
Soil Hydraulic Parameters ◽  
Soil Hydraulic ◽  
Definition Of

For all spatial scales, from pore through local and field, to a watershed, interaction of the land surface with the atmosphere will be one of the crucial topics in hydrology and environmental sciences over the forthcoming years. The recent lack of water in many parts of the world shows that there is an urgent need to assess our knowledge on the soil moisture dynamics. The difficulty of parameterization of soil hydrological processes lies not only in the nonlinearity of the unsaturated flow equation but also in the mismatch between the scales of measurements and the scale of model predictions. Most standard measurements of soil physical parameters provide information only at the local scale and highlight the underlying variability in soil hydrological characteristics. The efficiency of soil characteristic parameterization for the field scale depends on the clear definition of the functional relationships and parameters to be measured, and on the development of possible methods for the determination of soil characteristics with a realistic use time and effort. The soil’s hydraulic properties that affect the flow behavior can be expressed by a soil water retention curve that describes the relation between volumetric water content, θ(L3L3), and soil water pressure, h(L), plus the relation between volumetric water content and hydraulic conductivity, K(L/T). In the next section, the determination of soil hydraulic parameters is first discussed for local and field scale. Then, we show how the pore-scale processes can be linked to soil hydraulic properties. These properties are then used in some of the modern methods that use integral and superposition solutions of Richards’ equation for infiltration and water flow problems for both stable and preferential types of flows. Finally, some practical aspects for watersheds are discussed to highlight the difficulties encountered when large-scale predictions are needed.

The relevance of in-situ and laboratory characterization of sandy soil hydraulic properties for soil water simulations

2016 ◽  
Vol 534 ◽  
pp. 251-265 ◽  
Author(s):  
Meisam Rezaei ◽  
Piet Seuntjens ◽  
Reihaneh Shahidi ◽  
Ingeborg Joris ◽  
Wesley Boënne ◽  
...  
Keyword(s):  
Soil Water ◽  
Sandy Soil ◽  
Hydraulic Properties ◽  
Soil Hydraulic Properties ◽  
Laboratory Characterization ◽  
Soil Hydraulic
Sign in / Sign up

Export Citation Format

Share Document