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Three-Dimensional Modeling of the Hydrodynamics and Transport in Narragansett Bay
Citation:
Abdelrhman, M. Three-Dimensional Modeling of the Hydrodynamics and Transport in Narragansett Bay. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-15/152, 2015.
Impact/Purpose:
The main objective of this work is to develop the methodology to generate the hydrodynamics needed to predict the transport of constituents and properties that govern water quality and ecology in estuarine and coastal systems. Results from the developed methods can be used to derive water quality and ecology models to predict future conditions of estuarine and coastal systems. Decision makers can use such predictions to mitigate adverse effects due to atmospheric and demographic changes.
Description:
The work presented here addresses the specific needs of physical information required by tasks within the two SSWR projects: SSWR 2.3.A (Nutrient management for sustainability of upland and coastal ecosystems: Building a locally applicable management tool box for application across the US); and SSWR 6.1 (A systems analysis of Narragansett Bay, its watershed, and its stressors: The cumulative effects of previous management decisions on current ecosystem integrity). The main objective of this work is to develop the methodology to generate the hydrodynamics needed to predict the transport of constituents and properties that govern water quality and ecology in estuarine and coastal systems. The specific objective is to apply the developed methods to identify hydrodynamics and transport mechanisms in the Narragansett Bay, RI, to serve as a prototype for future implementation on other systems. This report presents the methodology to apply, calibrate, and validate a three-dimensional hydrodynamic model to provide the advection and dispersion mechanisms required by water quality and ecological models. The methodology is applied to Narragansett Bay, RI to generate sample predictions of hydrodynamics and transport for the year 2009. The same methodology can be applied to other years and periods of interest. The EPA-recommended Environmental Fluid Dynamics Code (EFDC) is chosen for this work.The approach presented here attempts to structure the model horizontal and vertical grid resolution to resolve the hydrodynamic, water quality, and ecological needs without any spatial or temporal aggregation. The temporally resolved sub-daily variations are intended to adequately address water quality needs (e.g., for temperature, light, oxygen, and phytoplankton growth). The process of calibration and validation of model results did not include any field monitoring programs; existing historical data were utilized. The generated hydrodynamics would be used with the water quality modules in the EPA’s Water Quality Analysis Simulation Program (WASP) to provide predictions for present and future scenarios of interest. The quality of the hydrodynamic predictions provided to WASP was maintained by a thorough calibration, validation, and performance evaluation of the hydrodynamic model. These data were internally calculated by EFDC and they included volume of segment, depth of segment, velocity through segment, flow along each flow path between segments, and dispersion along each flow path between segments.The report includes sections with detailed information, tables, and figures related to the physical setting and available data, model equations, and model configuration for Narragansett Bay, model calibration and validation, a summary of the skill parameters used to evaluate model performance, and a sample of model results. The summary and conclusion includes a brief discussion of the use of the hydrodynamic model results with the WASP water quality model and some suggestions to conduct hydrodynamic simulations of future scenarios.