Sensitivity analysis of unsaturated flow and contaminant transport with correlated parameters

summary This study conducts sensitivity and uncertainty analysis for predicting unsaturated flow and contaminant transport in a layered heterogeneous system. The objectives of this work are to: (1) examine the effects of parameter correlations on the sensitivity of unsaturated flow and contaminant transport and (2) assess the relative contributions of parameter uncertainties to the uncertainties of flow and transport at each hydrogeologic layer. Using the unsaturated zone (UZ) of Yucca Mountain (YM) in Nevada, USA, as an example, the study considers cases of independent and correlated parameters. A sampling-based regression method is used, when the model input parameters are independent, and a decomposition method is used for the correlated case. When the parameters are independent, the uncertainty in permeability has the largest contribution to the uncertainties in simulated percolation flux and mass of the reactive tracer arriving at the water table. For the percolation flux, the second largest contribution is from the van Genuchten a; the sorption coefficient of the reactive tracer is the second most important parameter for the tracer mass arrival uncertainty. The sensitivity to the sorption coefficient is larger in the layers of devitrified and zeolitic tuffs than in the layers of vitric tuff. Contributions of the uncertainties in van Genuchten n and porosity to the percolation flux and tracer transport uncertainties are larger in the case of correlated parameters compared with the case of independent parameters due to the correlations of n and porosity with the van Genuchten a and permeability, respectively. These results illustrate the significant effects of parameter correlations on the sensitivity and uncertainty of unsaturated flow and transport. The findings are of significance in facilitating future characterizations to reduce the parameter uncertainties and associated predictive uncertainties of flow and contaminant transport in unsaturated fractured porous media.

[1]  Karsten Pruess,et al.  Software qualification of selected TOUGH2 modules , 1996 .

[2]  L. Flint.  Physical and hydraulic properties of volcanic rocks from Yucca Mountain, Nevada , 2003 .

[3]  C. Fortuin,et al.  Study of the sensitivity of coupled reaction systems to uncertainties in rate coefficients. I Theory , 1973 .

[4]  Diane M. McKnight,et al.  Transport and cycling of iron and hydrogen peroxide in a freshwater stream: Influence of organic acids , 2003 .

[5]  Saltelli Andrea,et al.  Global Sensitivity Analysis: The Primer , 2008 .

[6]  A. Saltelli,et al.  A quantitative model-independent method for global sensitivity analysis of model output , 1999 .

[7]  Ming Ye,et al.  Assessment of radionuclide transport uncertainty in the unsaturated zone of Yucca Mountain , 2007 .

[8]  Jon C. Helton,et al.  Uncertainty and sensitivity analysis of chronic exposure results with the MACCS reactor accident consequence model , 1995 .

[9]  Jon C. Helton,et al.  Survey of sampling-based methods for uncertainty and sensitivity analysis , 2006, Reliab. Eng. Syst. Saf..

[10]  I. Sobol,et al.  About the use of rank transformation in sensitivity analysis of model output , 1995 .

[11]  L. Flint.  Characterization of hydrogeologic units using matrix properties, Yucca Mountain, Nevada , 1998 .

[12]  Samuel Boateng.  Probabilistic Unsaturated Flow along the Textural Interface in Three Capillary Barrier Models , 2007 .

[13]  Srikanta Mishra,et al.  Application of classification trees in the sensitivity analysis of probabilistic model results , 2003, Reliab. Eng. Syst. Saf..

[14]  Sensitivity of Solute Advective Travel Time to Porosities of Hydrogeologic Units , 2010, Ground water.

[15]  Gudmundur S. Bodvarsson,et al.  A Mountain‐Scale Model for Characterizing Unsaturated Flow and Transport in Fractured Tuffs of Yucca Mountain , 2004, Vadose Zone Journal.

[16]  Max D. Morris,et al.  Factorial sampling plans for preliminary computational experiments , 1991 .

[17]  I. Sobol.  Global sensitivity indices for nonlinear mathematical models and their Monte Carlo estimates , 2001 .

[18]  Gemma Manache,et al.  Identification of reliable regression- and correlation-based sensitivity measures for importance ranking of water-quality model parameters , 2008, Environ. Model. Softw..

[19]  H. H. Liu,et al.  Analysis of Hydrologic Properties Data , 2001 .

[20]  Jon C. Helton,et al.  A comparison of uncertainty and sensitivity analysis results obtained with random and Latin hypercube sampling , 2005, Reliab. Eng. Syst. Saf..

[21]  Yu-Shu Wu,et al.  Sensitivity analysis of hydrological parameters in modeling flow and transport in the unsaturated zone of Yucca Mountain, Nevada, USA , 2006 .

[22]  Ahmed E. Hassan,et al.  Modeling density-driven flow and radionuclide transport at an underground nuclear test: Uncertainty analysis and effect of parameter correlation , 2002 .

[23]  Daniel M. Tartakovsky,et al.  Multivariate sensitivity analysis of saturated flow through simulated highly heterogeneous groundwater aquifers , 2005, J. Comput. Phys..

[24]  Rafael Muñoz-Carpena,et al.  Parameter importance and uncertainty in predicting runoff pesticide reduction with filter strips. , 2010, Journal of environmental quality.

[25]  W. E. Wilson,et al.  Conceptual hydrologic model of flow in the unsaturated zone, Yucca Mountain, Nevada , 1984 .

[26]  Y.-T. Wu,et al.  CDF sensitivity analysis technique for ranking influential parameters in the performance assessment of the proposed high-level waste repository at Yucca Mountain, Nevada, USA , 2001, Reliab. Eng. Syst. Saf..

[27]  Van Genuchten,et al.  A closed-form equation for predicting the hydraulic conductivity of unsaturated soils , 1980 .

[28]  K. Shuler,et al.  Nonlinear sensitivity analysis of multiparameter model systems , 1977 .

[29]  Srikanta Mishra,et al.  Uncertainty and sensitivity analysis techniques for hydrologic modeling. , 2009 .

[30]  George Z. Gertner,et al.  Uncertainty and sensitivity analysis for models with correlated parameters , 2008, Reliab. Eng. Syst. Saf..

[31]  K. Pruess,et al.  TOUGH2 User's Guide Version 2 , 1999 .

[32]  J. Lang,et al.  Influence of hydraulic property correlation on predicted dense nonaqueous phase liquid source zone architecture, mass recovery and contaminant flux , 2004 .

[33]  Shoufan Fang,et al.  Estimation of sensitivity coefficients of nonlinear model input parameters which have a multinormal distribution , 2004 .

[34]  Alain Dassargues,et al.  Sensitivity analysis of prior model probabilities and the value of prior knowledge in the assessment of conceptual model uncertainty in groundwater modelling , 2009 .

[35]  Ming Ye,et al.  Incorporating layer- and local-scale heterogeneities in numerical simulation of unsaturated flow and tracer transport. , 2009, Journal of contaminant hydrology.

[36]  Sitakanta Mohanty,et al.  Sensitivity analysis of a complex, proposed geologic waste disposal system using the Fourier Amplitude Sensitivity Test method , 2001, Reliab. Eng. Syst. Saf..

[37]  F. J. Davis,et al.  Illustration of Sampling‐Based Methods for Uncertainty and Sensitivity Analysis , 2002, Risk analysis : an official publication of the Society for Risk Analysis.

[38]  Gudmundur S. Bodvarsson,et al.  Analyzing unsaturated flow patterns in fractured rock using an integrated modeling approach , 2007 .

[39]  Quanlin Zhou,et al.  Flow and transport in unsaturated fractured rock: effects of multiscale heterogeneity of hydrogeologic properties. , 2003, Journal of contaminant hydrology.

[40]  Ilya M. Sobol,et al.  Sensitivity Estimates for Nonlinear Mathematical Models , 1993 .

[41]  Joseph A. C. Delaney.  Sensitivity analysis , 2018, The African Continental Free Trade Area: Economic and Distributional Effects.

[42]  Rafael Muñoz-Carpena,et al.  GLOBAL SENSITIVITY AND UNCERTAINTY ANALYSES OF THE WATER QUALITY MODEL VFSMOD-W , 2007 .

[43]  Radionuclide Transport Models Under Ambient Conditions , 2001 .

[44]  Two‐Dimensional Sensitivity Analysis of Contaminant Transport in the Unsaturated Zone , 1999 .

[45]  Michael D. McKay,et al.  Nonparametric variance-based methods of assessing uncertainty importance , 1997 .

[46]  Jon C. Helton,et al.  Uncertainty and sensitivity analysis techniques for use in performance assessment for radioactive waste disposal , 1993 .

[47]  Walter A. Illman,et al.  Stochastic simulations of steady state unsaturated flow in a three-layer, heterogeneous, dual continuum model of fractured rock , 2005 .

[48]  T. Yeh,et al.  Sensitivity and moment analyses of head in variably saturated regimes , 1998 .

[49]  A. Saltelli,et al.  Non-parametric statistics in sensitivity analysis for model output: A comparison of selected techniques , 1990 .

[50]  Karsten Pruess,et al.  Numerical simulation of non-isothermal multiphase tracer transport in heterogeneous fractured porous media , 2000 .

[51]  Ming Ye,et al.  Numerical Evaluation of Uncertainty in Water Retention Parameters and Effect on Predictive Uncertainty , 2009 .

[52]  Yu-Shu Wu.  UZ Flow Models and Submodels , 2004 .

[53]  Stefano Tarantola,et al.  Sensitivity analysis practices: Strategies for model-based inference , 2006, Reliab. Eng. Syst. Saf..

[54]  Julien Jacques,et al.  Sensitivity analysis in presence of model uncertainty and correlated inputs , 2006, Reliab. Eng. Syst. Saf..

[55]  L. Pan.  Analysis of Hydrologic Properties Data , 2004 .

[56]  Garey A. Fox,et al.  Influence of flow concentration on parameter importance and prediction uncertainty of pesticide trapping by vegetative filter strips , 2010 .

[57]  Andrea Saltelli,et al.  An effective screening design for sensitivity analysis of large models , 2007, Environ. Model. Softw..