PARAMETER-IDENTIFICATION FOR GROUNDWATER-FLOW AND SOLUTE TRANSPORT SIMULATION - A COMPARISON OF L(1) AND L(2) ESTIMATORS

This paper presents a comparison between an L2 estimator and an L1 est imator for solving parameter identification problems in groundwater fl ow and solute transport simulation. The L1 estimator is formulated usi ng a weighted L1-norm as the error measure between the vector of the o bserved hydraulic heads and solute concentrations and the vector of th e simulated heads and concentrations. The simulation model is comprise d of a finite element formulation for steady-state groundwater flow an d solute transport in a two-dimensional vertically averaged aquifer sy stem. The gradients of the state variables with respect to the paramet ers are computed using a state sensitivity method. Posterior statistic al inferences are conducted. The solutions to two sets of hypothetical groundwater parameter estimation problems illustrate that the L1 esti mator is more robust than the L2 estimator in handling observation dat a containing certain outliers.