Use of Global Sensitivity Analysis to Help Assess Unsaturated Soil Hydraulic Parameters

Younès, Anis; Mara, Thierry A.; Fajraoui, Noura; Lehmann, François; Belfort, Benjamin; Beydoun, H.

doi:10.2136/vzj2011.0150

Cited by 32 publications

(31 citation statements)

References 58 publications

(67 reference statements)

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“…It demonstrates that the goodness of fitting of observed data is sensitive to α, n and K 0 , but insensitive to the parameters θ r and θ s . And the parameters θ r and θ s have higher uncertainties than those of α, n and K 0 , which is consistent with Shi et al (2015) and Younes et al (2013).…”

Section: Resultssupporting

confidence: 76%

Quantifying soil hydraulic properties and their uncertainties by modified GLUE method

Yan¹,

Liu²,

Zhang³

et al. 2017

International Agrophysics

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A b s t r a c t. Nonlinear least squares algorithm is commonly used to fit the evaporation experiment data and to obtain the 'optimal' soil hydraulic model parameters. But the major defects of nonlinear least squares algorithm include non-uniqueness of the solution to inverse problems and its inability to quantify uncertainties associated with the simulation model. In this study, it is clarified by applying retention curve and a modified generalised likelihood uncertainty estimation method to model calibration. Results show that nonlinear least squares gives good fits to soil water retention curve and unsaturated water conductivity based on data observed by Wind method. And meanwhile, the application of generalised likelihood uncertainty estimation clearly demonstrates that a much wider range of parameters can fit the observations well. Using the 'optimal' solution to predict soil water content and conductivity is very risky. Whereas, 95% confidence interval generated by generalised likelihood uncertainty estimation quantifies well the uncertainty of the observed data. With a decrease of water content, the maximum of nash and sutcliffe value generated by generalised likelihood uncertainty estimation performs better and better than the counterpart of nonlinear least squares. 95% confidence interval quantifies well the uncertainties and provides preliminary sensitivities of parameters.

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Section: Resultssupporting

confidence: 76%

Quantifying soil hydraulic properties and their uncertainties by modified GLUE method

Yan¹,

Liu²,

Zhang³

et al. 2017

International Agrophysics

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“…Therefore, the saturated hydraulic conductivity was estimated by model calibration of the outflow during drainage (Table 1), and the other flow parameters remained unchanged. The obtained hydraulic parameters were slightly different from one experiment to another (Table 1) and were consistent with previous works (Younes et al, 2013) as well as the value estimated using the Rosetta pedotransfer function (Schaap et al, 2001) calculation (0.016 cm/s). Due to the boundary conditions of the experiment (prescribed flux at the top, prescribed pressure at the bottom), the differences in hydraulic conductivity led to different pressure distributions over the column and therefore different water content and water velocity profiles (Fig.…”

Section: Water Content Profilessupporting

confidence: 89%

Modeling the effects of water content on TiO2 nanoparticles transport in porous media

Toloni

Lehmann

Ackerer

2016

Journal of Contaminant Hydrology

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The transport of manufactured titanium dioxide (TiO2, rutile) nanoparticles (NP) in porous media was investigated by metric scale column experiments under different water saturation and ionic strength (IS) conditions. The NP breakthrough curves showed that TiO2 NP retention on the interface between air and water (AWI) and the interface between the solid and the fluid (SWI) is insignificant for an IS equal to or smaller than 3mM KCl. For larger IS, the retention is depending on the water content and the fluid velocity. The experiments, conducted with an IS of 5mM KCl, showed a significantly higher retention of NP than that observed under saturated conditions and very similar experimental conditions. Water flow was simulated using the standard Richards equation. The hydrodynamic model parameters for unsaturated flow were estimated through independent drainage experiments. A new mathematical model was developed to describe TiO2 NP transport and retention on SWI and AWI. The model accounts for the variation of water content and water velocity as a function of depth and takes into account the presence of the AWI and its role as a NP collector. Comparisons with experimental data showed that the suggested modeled processes can be used to quantify the NPs retentions at the AWI and SWI. The suggested model can be used for both saturated and unsaturated conditions and for a rather large range of velocities.

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“…In which regions of the parameter range is the sensitivity the largest? These questions can be answered with univariate effects, originally introduced by Younes, Mara, Fajraoui, Lehmann, Belfort, and Beydoun (2013). Univariate effects can be defined as the conditional expectation of a quantity of interest as a function of a single parameter, where expectations are taken over all other parameters:…”

Section: Pc Expansion-basedmentioning

confidence: 99%

Uncertainty quantification and global sensitivity analysis for economic models

Harenberg¹,

Marelli²,

Sudret³

et al. 2019

Quantitative Economics

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We present a global sensitivity analysis that quantifies the impact of parameter uncertainty on model outcomes. Specifically, we propose variance-decomposition-based Sobol' indices to establish an importance ranking of parameters and univariate effects to determine the direction of their impact. We employ the stateof-the-art approach of constructing a polynomial chaos expansion of the model, from which Sobol' indices and univariate effects are then obtained analytically, using only a limited number of model evaluations. We apply this analysis to several quantities of interest of a standard real-business-cycle model and compare it to traditional local sensitivity analysis approaches. The results show that local sensitivity analysis can be very misleading, whereas the proposed method accurately and efficiently ranks all parameters according to importance, identifying interactions and nonlinearities.

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Use of Global Sensitivity Analysis to Help Assess Unsaturated Soil Hydraulic Parameters

Abstract: International audienc

Cited by 32 publications

References 58 publications

Quantifying soil hydraulic properties and their uncertainties by modified GLUE method

Quantifying soil hydraulic properties and their uncertainties by modified GLUE method

Modeling the effects of water content on TiO2 nanoparticles transport in porous media

Uncertainty quantification and global sensitivity analysis for economic models

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