Site and size optimization of contaminant sources in surface water systems

A numerical method is developed to minimize the environmental impact of one or multiple contaminant point sources in a vertically mixed river or estuary. The algorithm is based on a finite-element solution of the adjoint to the fate and transport equation that permits efficient selection of optimal locations and mass loadings of outfalls in the presence of tidal action, secondary currents, river branches, and other two-dimensional factors. The evaluation is based on the cumulative effects of contaminants in one or more arbitrary target points in the system. The model is validated by comparison to repeated trial solutions and is shown to yield information comparable to that resulting from a large number of hypothetical simulations. Practical applications are presented for the Fox River and the upper Potomac Estuary verifying the method's applicability to rivers of arbitrary geometry and bathymetry.