Groundwater flow pattern identification using the adjoint method in a particle model for pollutant transport

In this paper, a groundwater flow pattern identification algorithm using contamination measurements is developed for particle models modelling transport of pollutants in groundwater. The parameter estimation problem is formulated as an optimization problem and is solved with a gradient based algorithm. For each generated particle track, the adjoint track is determined. These adjoint tracks are used to efficiently compute the gradient of the objective function. The approach of estimating the velocity fields is discussed and is illustrated with hypothetical applications. Furthermore, the performance of the algorithm is tested with different number of particles and more parameters.