Statistical analysis of spatial variability in unsaturated flow parameters

Russo, David; Bouton, Moshe

doi:10.1029/92wr00669

Cited by 221 publications

(190 citation statements)

References 55 publications

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“…Because a large number of tests were conducted during construction, geometric means are reported for K s and  and arithmetic means are reported for n,  s , and  r . Geometric means are reported for K s and  because they are log-normally distributed, whereas arithmetic means are reported for n,  s , and  r because they are normally distributed (Russo and Bouton 1992, Hills et al 1992, Benson 1993, Gurdal et al 2003. Standard deviations () are also reported in Table 2, with standard deviations of lnK s and ln reported for K s and to correspond with the geometric means.…”

Section: Results and Analysismentioning

confidence: 99%

Postconstruction Changes in the Hydraulic Properties of Water Balance Cover Soils

Benson

Sawangsuriya

Trzebiatowski

et al. 2007

J. Geotech. Geoenviron. Eng.

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Hydraulic properties of soils used for water balance covers measured at the time of construction and 1-4 yrs after construction are compared to assess how the hydraulic properties of cover soils change over time as a result of exposure to field conditions. Data are evaluated from ten field sites in the United States that represent a broad range of environmental conditions. The comparison shows that the saturated hydraulic conductivity (K s ) can increase by a factor of 10,000, saturated volumetric water content ( s ) by a factor of 2.0, van Genuchten's  parameter by a factor of 100, and van

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Section: Results and Analysismentioning

confidence: 99%

Postconstruction Changes in the Hydraulic Properties of Water Balance Cover Soils

Benson

Sawangsuriya

Trzebiatowski

et al. 2007

J. Geotech. Geoenviron. Eng.

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“…A correlation scale of 30 m in the horizontal directions and 2 m in the vertical were used to create a layered structure, typical sedimentary environment for a loosely consolidated unconfined aquifer. According to the analysis of field data by Russo and Bouton [1992], the variability of unsaturated parameters is usually smaller than that of the K S . The statistics of S S from previous studies is not readily available.…”

Section: Numerical Model Setupmentioning

confidence: 99%

“…m is related to the tortuosity of the soil and is assumed to be zero. We chose these models because the spatial variability of parameters in equations (3) and (4) in the field has been well documented [see Russo and Bouton, 1992].…”

Section: Equation For Variably Saturated Groundwater Flowmentioning

confidence: 99%

Joint interpretation of sequential pumping tests in unconfined aquifers

Mao

Yeh

Wan

et al. 2013

Water Resources Research

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[1] In this study, we developed a stochastic estimator for characterizing the hydraulic heterogeneity in both unsaturated and saturated zones of unconfined aquifers using transient drawdown data from sequential pumping tests. This estimator was built upon the successive linear estimator by Yeh et al. (1996), the simultaneous successive linear estimator by Xiang et al. (2009), and the 3-D finite element program for flow and transport through heterogeneous media by Srivastava and Yeh (1992). The estimator was tested afterward using simulated data sets of sequential pumping tests in a synthetic unconfined aquifer where saturated conductivity, specific storage, saturated water content, and pore-size distribution parameter vary spatially in three dimensions. Test results show that the estimator is able to produce parameter fields that capture the overall 3-D pattern of the true heterogeneous parameter fields. We subsequently validated the estimated parameter fields by assessing their ability to predict drawdowns during an independent pumping test, which was not used during the estimation phase. Results of the validation show that the predicted drawdowns based on the estimated heterogeneous parameter fields are in close agreement with the true drawdowns. In addition, predicted drawdowns based on the parameter fields from the joint interpretation are superior to those based on the parameters estimated from the homogeneous conceptual model. Lastly, while many field experiments are necessary to fully assess the robustness of this estimator and sequential pumping tests, results of this study suggest they are a promising characterization technique for unconfined aquifers.

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“…Since spatial variations in the parameters such as Ss, Os, Or, OIL, and Oi r are generally small [Russo and Bouton, 1992], the parameters are considered constant in space. Subsequently, we regard only the log-transformed saturated conductivity and the pore size distribution parameter (i.e., LnK s and Lnoi) as random fields, consisting of a mean and pertur- …”

Section: Equations Of Flow and Solute Transport In Variably Saturatedmentioning

confidence: 99%

Cokriging estimation of the conductivity field under variably saturated flow conditions

Yeh²

1999

Water Resources Research

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Abstract. A linear estimator, cokriging, was applied to estimate hydraulic conductivity, using pressure head, solute concentration, and solute arrival time measurements in a hypothetical, heterogeneous vadose zone under steady state infiltrations at different degrees of saturation. Covariances and cross-covariances required by the estimator were determined by a first-order approximation in which sensitivity matrices were calculated using an adjoint state method, The effectiveness of the pressure, concentration, and arrival time measurements for the estimator were then evaluated using two statistical criteria, L • and L 2 norms, i.e., the average absolute error and the mean square error of the estimated conductivity field. Results of our analysis showed that pressure head measurements at steady state flow provided the best estimation of hydraulic conductivity among the three types of measurements. In addition, head measurements of flow near saturation were found more useful for estimating conductivity than those at low saturations. The arrival time measurements do not have any significant advantage over concentration. Factors such as variability, linearity, and ergodicity were discussed to explain advantage and limitation of each type of data set. Finally, to take advantage of different types of data set (e.g., head and concentration), a computationally efficient estimation approach was developed to combine them sequentially to estimate the hydraulic conductivity field. The conductivity field estimated by using this sequential approach proves to be better than all the previous estimates, using one type of data set alone. IntroductionDuring the past decades, the cokriging technique has been applied extensively to many studies of subsurface hydrology. timates of the heterogeneous conductivity field. On the other hand, Yeh et al. [1995, 1996] proposed iterative cokriging techniques for nonlinear systems in which the requirement of unbiasedness and minimum variance were imposed during each iteration. By incorporating the nonlinear relationship between head and conductivity in groundwater flow systems, the estimated conductivity field revealed more detailed heterogeneity than using the linear model and more closely resembled the true field. This iterative approach was further extended to unsaturated flow by Zhang and Yeh [1997] to estimate parameters for unsaturated hydraulic conductivity in the vadose zone. Similarly, a quasi-linear geostatistical approach was presented by Kitanidis [1995] in an attempt to incorporate the nonlinear relationship between the parameter and secondary information of the subsurface flow system.In spite of the advance in parameter estimation techniques, a practical question remains regarding what kind of measurements (e.g., head, concentration, or other variables) are most useful for estimating the hydrological parameters. Several attempts to address this issue were carried out in the past. For example, Yeh and Zhang [1996] found that pressure head measurements can improve estimates of s...

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Statistical analysis of spatial variability in unsaturated flow parameters

Cited by 221 publications

References 55 publications

Postconstruction Changes in the Hydraulic Properties of Water Balance Cover Soils

Postconstruction Changes in the Hydraulic Properties of Water Balance Cover Soils

Joint interpretation of sequential pumping tests in unconfined aquifers

Cokriging estimation of the conductivity field under variably saturated flow conditions

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