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Element 5 - Demonstrating the model

To demonstrate the application of the GIS-based hydrologic model, we undertook a simulation using a synthetic storm period. The simulation began with baseflow conditions and no rainfall. This was followed by two distinct rainstorms punctuated by a period of no rain when the river network returned to baseflow conditions. The first rainstorm lasted for 32 hours and was of low intensity (maximum rainfall rate less than 1 in/hr), whereas the second rainstorm lasted 42 hours and was of much higher intensity (maximum rainfall rate greater than 1 in/hr). There are three sites within the east arm of the Little Calumet River where combined sewage overflows (CSOs) are known to occur -- (Elden Kuehl Pollution Control Facility, Chesterton Utilities Wastewater Treatment Plant, and Portage Municipal Wastewater Treatment Plant) -- and one site within the Trail Creek watershed -- (Michigan City Sanitary District). When the rainfall exceeded 1 in/hr during the second storm period, CSOs were imposed on reaches where those release points exist. The CSO was simulated by altering the mixing equation for the four stations to include an additional source term. The amount of bacteria released was adjusted until concentrations in the reaches achieved values that are known to be associated with CSOs.

The results of the demonstration simulations are presented in four Macromedia Flash applications. The first two applications are audio-visual presentations of the temporal and spatial variability of E. coli concentrations and streamflow during the entire simulation in each of the two study watersheds. The other two applications show hydrographs of streamflow and E. coli concentrations at sequences of locations within each watershed, moving downstream from the headwatersof each watershed to their outlets. The applications, each of which is about 8 Mb in size, are available upon request.

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