No abstract

Generally, event based rainfall-runoff model calibration and verification is a laborious and expensive activity. With the availability of long term continuous flow meter and rainfall data and faster computers and software, models can now be calibrated to a long term flow record spanning from few months to several years. The practice of model calibration for large and complex regional systems is evolving over the years away from the conventional event based two step calibration and verification process to a more efficient single step continuous calibration process. This paper describes and compares the event and continuous calibration methods. It also presents information and comparison of various statistical methods to objectively quantify the goodness-of-fit statistics for model calibration that can be used in continuous calibration. Examples are provided from the Metropolitan Sewer District of Greater Cincinnati (MSDGC) SWMM model which is one of the largest SWMM model in the world.

The Metropolitan Sewer District of Greater Cincinnati's (MSD) SWMM model is one of the largest SWMM models in the world. In developing this model, MSD advanced the state-of-the-art in collection system modeling in a number of areas including the size and scope of the model, the application of radar rainfall data, the use of water consumption data to estimate dry weather flows, and the use of GIS for model development. It provided MSD with an extraordinary tool to evaluate existing and projected conditions and to use a modeled problem with a modeled solution approach for consent decree compliance. This paper provides the history, features and applications of the MSD SWMM model. Modeling challenges and lessons learned are also discussed.

No abstract

Rainfall dependent inflow and infiltration (RDm into sanitary sewer systems has long been recognized as a source of operating problems in wastewater collection and treatment systems. RDll can cause sanitary sewer flows to increase during wet weather to rates that exceed the hydraulic capacity of the wastewater collection system in one or more locations. When this occurs, the hydraulic grade line is elevated to a level that can cause sanitary sewer overflows (SSOs), with the resulting surcharged flows entering basements, overflowing to the street surface through manholes, or discharging to nearby streams through constructed overflow outfalls. RDII also contnbutes to serious operating problems at wastewater treatment facilities, including hydraulic overloading and disruption of biological and other plant processes. Thus, the need to understand and control the RDll problem is crucial. Two very different hydrologic processes are involved in the sanitary and combined sewer systems in response to wet weather. The more straightforward and well-understood process is that of the combined sewer system, where surface runoff is the dominant response. However, hydrologic processes in the sanitary sewer system are not as well understood, nor are they as accurately modeled with reasonably available data. As a result, empirical data are used to estimate the hydrologic response in the sanitary sewer system, rather than detenninistically model the physical process. Attempts to simulate the sanitarysewerresponseusing algorithms and tools developed for simulating combined sewer response typically yield less reliable results and solutions.