Flux-based contaminant transport in a GIS environment

A computationally efficient method for predicting contaminant mass flux to a specified boundary is presented. The method combines streamlines calculated using the analytic element method with a first-passage-time (residence time) approach to calculating mass flux. Computations exploit convolution in Laplace space with numerical inversion. The technique is carried out in a geographic information system (GIS) that takes full advantage of widely available digital hydrologic data. The flux-based estimations allow efficient coupling of contaminant mass across hydrologic interfaces. This combined approach is useful for rapid but approximate transport computations either at the local or regional scale. We demonstrate the approach by considering nitrogen-loading to surface water due to surface application of animal feedlot waste. Nitrogen is predicted to migrate through ground-water, resulting in a long-term loading to nearby streams. The object-oriented implementation of this modeling approach improves integration between the GIS and the transport modeling, allowing transport results to be returned to the database.