Abstract

Flow data collected from over twenty metered sites in Detroit, Michigan are used to determine the source of flows from districts tributary to the Detroit Water & Sewerage Department (DWSD) collection system through a flow balance analysis. Criteria developed for selecting data include precipitation, snowmelt, and basin dewatering. The Greater Detroit Regional Sewer System (GDRSS) model, a hydraulic and hydrologic model of Detroit's sewer collection system, was used to refine the rainfall-based criteria. Specifically, it was used to determine the time required for the system to return to dry weather flow (DWF) conditions after one or a series of rainfall events. As a result of model simulations, relationships were developed to represent time-to-dry as a function of the rainfall amount of single- or multiple-day rainfall events. These relationships are a key component of the overall data selection for the flow balance, and provide an objective approach to characterizing DWF in the DWSD collection system.

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