A New Zonation Algorithm with Parameter Estimation Using Hydraulic Head and Subsidence Observations

Department of Geosciences, Virginia Tech, Blacksburg, VA 24061
Ground Water (Impact Factor: 2.31). 08/2013; 52(4). DOI: 10.1111/gwat.12102
Source: PubMed


Parameter estimation codes such as UCODE_2005 are becoming well-known tools in groundwater modeling investigations. These programs estimate important parameter values such as transmissivity (T) and aquifer storage values (Sa ) from known observations of hydraulic head, flow, or other physical quantities. One drawback inherent in these codes is that the parameter zones must be specified by the user. However, such knowledge is often unknown even if a detailed hydrogeological description is available. To overcome this deficiency, we present a discrete adjoint algorithm for identifying suitable zonations from hydraulic head and subsidence measurements, which are highly sensitive to both elastic (Sske ) and inelastic (Sskv ) skeletal specific storage coefficients. With the advent of interferometric synthetic aperture radar (InSAR), distributed spatial and temporal subsidence measurements can be obtained. A synthetic conceptual model containing seven transmissivity zones, one aquifer storage zone and three interbed zones for elastic and inelastic storage coefficients were developed to simulate drawdown and subsidence in an aquifer interbedded with clay that exhibits delayed drainage. Simulated delayed land subsidence and groundwater head data are assumed to be the observed measurements, to which the discrete adjoint algorithm is called to create approximate spatial zonations of T, Sske , and Sskv . UCODE-2005 is then used to obtain the final optimal parameter values. Calibration results indicate that the estimated zonations calculated from the discrete adjoint algorithm closely approximate the true parameter zonations. This automation algorithm reduces the bias established by the initial distribution of zones and provides a robust parameter zonation distribution.

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Available from: Thomas J. Burbey, Jan 07, 2014
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    ABSTRACT: Las Vegas Valley has had a long history of groundwater development and subsequent surface deformation. Much research has been done to estimate parameters within the Las Vegas basin, but this research represents the first effort to use parameter estimation techniques to inversely calibrate hydrogeologic aquifer parameters for the principle aquifer of the entire basin. Three different inversion strategies are invoked to determine the most accurate and computationally efficient method for estimating transmissivities (T) and elastic and inelastic skeletal storage coefficients (Ske and Skv) at the basin scale: the zonation method (ZM), the adaptive multi-scale method and the Differential Evolution Adaptive Metropolis Markov chain Monte Carlo scheme (DREAM MCMC). The three inversion methods are compared and contrasted based on quantitative measurements of model fit, computational efficiency and user flexibility. The results indicate that overall, the adaptive multi-scale method, which is able to efficiently reconstruct the T , Ske and Skv zones while providing more flexibility and accuracy than the other two methods, is the best strategy for calibrating optimal model parameters and providing a framework for developing an accurate hydrogeologic model for Las Vegas Valley.
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