| Summary: | 碩士 === 國立交通大學 === 環境工程所 === 89 === A method using extended Kalman filter (EKF) and cubic spline is proposed to identify the aquifer parameters in both confined and unconfined aquifer systems. The Theis solution combined with EKF, using the interpolated drawdown data produced by cubic spline, can optimally determine the parameters for confined aquifer through the recursive filtering process. In an unconfined system, Neuman’s model is employed by the same manner as the Theis solution to determine the aquifer parameters.
The proposed method can quickly identify the parameters, using only part of observed drawdown data and the obtained parameters are shown to achieve good accuracy. Thus, the lengthy pumping test can be shortened. In addition, the comparisons of analyzing results between using nonlinear least-squares combined with finite-difference Newton’s method (NLN) and EKF for various initial guess values are presented. The EKF is proven to have a wider range of initial guess values, though the accuracy of the result is not so good as that by using NLN. Finally, during the determination of aquifer parameters, specific yield almost maintains constant at the beginning of the identification process until the drawdown curve starts flattening. During the flat period, specific yield jumps initially and then approaches a certain value. This identification process reflects the effect of gravity drainage on the drawdown curve and conforms to the physical nature of the unconfined aquifer.
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