A wetland model incorporating overland and channel flow, solute transport and surface/ground water interactions

The crucial role played by surface water/ground water interactions in water resources and hydrologic applications has only recently been recognized. The interaction with ground water occurs with all types of surface waters such as streams, lakes, and wetlands. Modeling the interactions between ground water and surface water necessitates a detailed understanding of flood wave propagation, including conceptual models for its prediction, governing differential equations and their numerical solution. For example, explicit and implicit finite difference numerical methods are developed as part of this thesis to solve kinematic and diffusion waves for both overland and open channel flows. Furthermore, an analytical solution was derived for diffusion waves specifically applied to overland flow problems. Comparison of results on synthetic examples shows that numerical and analytical solutions are in good agreement. A comprehensive wetland model WETland Solute TrANsport Dynamics (WETSAND) was developed which has both flow and solute transport components, incorporates surface/ground water interactions, and accounts for upstream contributions from urbanized areas. The effect of wetlands on storm water runoff was investigated by routing the overland flow through the wetland area, collecting the runoff within the stream and transporting it to the receiving water. The computed velocity profiles were used to predict the distribution of pollutant concentrations in the wetland areas. The water quality component solves the advection-dispersion equation for several nitrogen and phosphorus constituents. In addition, output from the newest version of the EPA Storm Water Management Model (SWMM5) was incorporated into this wetland model to simulate the runoff quantity and quality time series flowing into the wetland from upstream urban areas. An application of the model to the Duke University West Campus and the Duke University constructed wetland area in the Sandy Creek watershed is presented. Finally, a mathematical model was developed to show the effect of interactions between streams and ground water on stream solute transport. This model represents the movement of water through the hyporheic zone in order to explain the physics of water exchange between the surface water and the porous media in a mechanistic manner. This new model was verified with measured data from the Uvas Creek experiment conducted by Bencala and Walters.