Philadelphia’s Tidal Delaware River Receiving Water Models: Integrating Collection System Modeling, Wastewater Management, and Water Supply

Abstract Submission: Philadelphia Water Department (PWD) developed three-dimensional hydrodynamic and water quality models of the tidal Delaware River to better understand and manage Philadelphia’s water resources. These grid-based receiving water models were initially developed for PWD’s combined sewer overflow (CSO) long-term control plan using the US EPA Environmental Fluid Dynamics Code (EFDC) model to meet regulatory requirements. They are continuously updated and expanded to increase understanding of hydrodynamic and water quality characteristics and complex processes in Philadelphia’s receiving waters. Extensive monitoring surveys inform model validation. While bacteria and dissolved oxygen models were initially developed to evaluate water quality impacts of CSO, PWD later developed a salinity model to understand how watershed conditions impact river salinity for water supply planning. These models have become critical tools for evaluating regulatory compliance and management strategies impacting regional water resources.
This presentation will provide an overview of the tidal Delaware River models and describe how they are used to address PWD’s current and future needs, emphasizing the advantages of using models as tools for understanding, planning, and reacting to emerging water quality issues for a utility managing wastewater, stormwater, and drinking water resources. Planning for the future of Philadelphia’s water resources includes anticipating variable conditions from climate change, sea level rise, and changes to water quality regulations regarding CSO control and wastewater effluent limits. PWD has stayed ahead of these concerns through improved understanding of receiving water impacts due to its early and continuous investment in monitoring and modeling.

Learning Objectives/Expected Outcome (Optional) : Understanding of the advantages of using receiving water models for watershed planning.