Modeling the impacts of stormwater runoff on small streams, requires that the prediction model has the capability of simulating the behavior of the hydrologic and water quality components of the stream system. Development of such a model involves coupling the equations for pollutant transport during unsteady flow with the appropriate flood routing equations. The decision on which equations to choose requires a full understanding of the pollutant transport and hydrograph dispersion processes.
This research was undertaken to develop a rigorous theoretical evaluation of the pollutant transport and hydrograph dispersion processes during unsteady flow, and to recommend a suitable model for simulating the impact of stormwater on small streams. It was determined that the one dimensional convective - dispersive equation for tracers (pollutants) coupled with a form of the diffusive wave model for unsteady streamflow would provide the basis for a simulation model that is both simple and consistent with the principal transport processes. Evaluation of the dynamic terms in the momentum equation yielded general estimators to model parameters and established that the Muskingum routing model is consistent with the modified diffusive wave model developed during this research.
The coefficient for hydrograph dispersion was tested on tracer dispersion data and was found to be a reasonable prediction equation for channels with top widths less than 115 feet and bed slopes greater than 1.6 feet per mile. Most small streams satisfy these conditions.
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The work upon which this report is based was supported in part by funds provided by the Office of Water Research and Technology, United States Department of the Interior, Washington, D.C., as authorized by the Water Research and Development Act of 1978. Public Law 95-467.
Meadows, Michael E., "Mathematical Model for Water Quality in Streams Impacted by Point and Nonpoint Source Pollution" (1981). KWRRI Research Reports. 77.