A Modified Gauss‐Newton Method for Aquifer Parameter Identification

The accuracy of parameter estimation procedures is evaluated for a modified Gauss‐Newton method applied to transient ground‐water flow. Three different approaches of evaluating the sensitivity coefficient matrix are examined, including influence coefficient, sensitivity equation, and variational approaches. The performance of each of the techniques is evaluated by applying a common synthetic data set. The latter two techniques are shown to perform with least sensitivity to starting parameters and extraneous sampling noise. Where either random or systematic noise is added to the time‐series data set, the resulting predictions become increasingly more sensitive to the form of the starting transmissivity vector. It is concluded that the modified Gauss‐Newton method is attractive because of its simplicity, high rate of convergence, and modest computational demands, especially when the number of the parameters to be identified is not large.