Presentation Abstract

3-D Hydrodynamic Modelling of Lower Fraser River Shaheli Masoom and Li Gu Environmental Management and Quality Control Division, Liquid Waste Services Department, Metro Vancouver, Burnaby B.C., Canada Email: shaheli.masoom@metrovancouver.org; li.gu@metrovancouver.org Abstract Lower Fraser River, the largest fresh water inflow into the Salish Sea, receives discharges from the urban area of the Metro Vancouver region, along with treated effluent from three of Metro Vancouver Regional District’s (MVRD) wastewater treatment plants. The complex dynamics of this estuarine river plays a crucial role in the fate and effect of these liquid discharges. In particular, the mixing of fresh river water with dense saline ocean water results in flow stratification and a dynamic salt wedge, necessitating a three dimensional computational modeling approach to predict the fate and effect of treatment plant effluent and emergency sewer overflow discharges into the river. This paper describes the development of a three dimensional (3-D) hydrodynamic and transport model for the Lower Fraser River, using Danish Hydraulic Institute’s MIKE3 FM software. The domain extends from Mission to Sand Head with about 30,000 flexible mesh elements horizontally with refined meshes in zones of interest. A combination of sigma and z-layer is used for vertical discretization. The model was calibrated and validated successfully using measurements of water level, buoy measured current-salinity and river discharges from ADCP transects. For all the calibration and validation runs, the predicted flow split of 12-13% to North Arm located at Fraser bifurcation was well within the published values of 10-15%. The preliminary model results provide an improved understanding of the salt wedge dynamics with variable tide and river conditions. The prediction of tracer dye (Rhodamine) transport from Annacis Island Wastewater Treatment Plant indicates that the plume is well mixed vertically not far downstream from the edge of the initial dilution zone and has a tendency to move in a narrow band hugging the north shore of the river channel, consistent with previous field observations.

Session Title

Water Quality and Hydrodynamics

Keywords

Hydrodynamic model, Fraser river

Conference Track

SSE1: Habitat Restoration and Protection

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE1-489

Start Date

4-4-2018 1:30 PM

End Date

4-4-2018 1:45 PM

Type of Presentation

Oral

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type

text

Language

English

Format

application/pdf

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Apr 4th, 1:30 PM Apr 4th, 1:45 PM

3D hydrodynamic modeling of Lower Fraser River

3-D Hydrodynamic Modelling of Lower Fraser River Shaheli Masoom and Li Gu Environmental Management and Quality Control Division, Liquid Waste Services Department, Metro Vancouver, Burnaby B.C., Canada Email: shaheli.masoom@metrovancouver.org; li.gu@metrovancouver.org Abstract Lower Fraser River, the largest fresh water inflow into the Salish Sea, receives discharges from the urban area of the Metro Vancouver region, along with treated effluent from three of Metro Vancouver Regional District’s (MVRD) wastewater treatment plants. The complex dynamics of this estuarine river plays a crucial role in the fate and effect of these liquid discharges. In particular, the mixing of fresh river water with dense saline ocean water results in flow stratification and a dynamic salt wedge, necessitating a three dimensional computational modeling approach to predict the fate and effect of treatment plant effluent and emergency sewer overflow discharges into the river. This paper describes the development of a three dimensional (3-D) hydrodynamic and transport model for the Lower Fraser River, using Danish Hydraulic Institute’s MIKE3 FM software. The domain extends from Mission to Sand Head with about 30,000 flexible mesh elements horizontally with refined meshes in zones of interest. A combination of sigma and z-layer is used for vertical discretization. The model was calibrated and validated successfully using measurements of water level, buoy measured current-salinity and river discharges from ADCP transects. For all the calibration and validation runs, the predicted flow split of 12-13% to North Arm located at Fraser bifurcation was well within the published values of 10-15%. The preliminary model results provide an improved understanding of the salt wedge dynamics with variable tide and river conditions. The prediction of tracer dye (Rhodamine) transport from Annacis Island Wastewater Treatment Plant indicates that the plume is well mixed vertically not far downstream from the edge of the initial dilution zone and has a tendency to move in a narrow band hugging the north shore of the river channel, consistent with previous field observations.