A COMPOSITE L1 PARAMETER ESTIMATOR FOR MODEL-FITTING IN GROUNDWATER-FLOW AND SOLUTE TRANSPORT SIMULATION

This paper proposes a composite L1 parameter estimator to solve the in verse problems in groundwater flow and solute transport modeling. The estimator is formulated using a weighted L1 norm as the error measure between the vector of the observed hydraulic heads and solute concentr ations and the corresponding vector of the heads and concentrations co mputed from a finite element model for steady state groundwater flow a nd solute transport in a two-dimensional areal confined aquifer system . The parameters currently considered are the hydraulic conductivities , the dispersivities, the porosities of the aquifer system, and the so lute source concentration(s). The gradients of the state variables wit h respect to the parameters are computed analytically using a formulat ion stemming from the finite element model for the state variables. Th e solutions to two hypothetical groundwater parameter estimation probl ems are presented to illustrate that the proposed estimator does have the property of being fairly accurate and, more significantly, being r obust in handling observation data containing certain outliers.