USGS Michigan Water Science Center
Augmenting Two-Dimensional Hydrodynamic Simulations with Measured Velocity Data
to Identify Flow Paths as a Function of Depth on Upper St. Clair River in the Great
Lakes Basin
In cooperation with the American Water Works Association Research Foundation
By: D.J. Holtschlag and J.A. Koschik
US Geological Survey Scientific Investigations Report 2005-5081
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Abstract
Upper St. Clair River, which receives outflow from Lake Huron, is characterized by flow velocities that exceed 7 feet per second and significant channel curvature that creates complex flow patterns downstream from the Blue Water Bridge in the Port Huron, Michigan, and Sarnia, Ontario, area. Discrepancies were detected between depth-averaged velocities previously simulated by a two-dimensional (2D) hydrodynamic model and surface velocities determined from drifting buoy deployments. A detailed ADCP (acoustic Doppler current profiler) survey was done on Upper St. Clair River during July 1-3, 2003, to help resolve these discrepancies.
As part of this study, a refined finite-element mesh of the hydrodynamic model used to identify source areas to public water intakes was developed for Upper St. Clair River. In addition, a numerical procedure was used to account for radial accelerations, which cause secondary flow patterns near channel bends. The refined model was recalibrated to better reproduce local velocities measured in the ADCP survey. ADCP data also were used to help resolve the remaining discrepancies between simulated and measured velocities and to describe variations in velocity with depth.
Velocity data from ADCP surveys have significant local variability, and statistical processing is needed to compute reliable point estimates. In this study, velocity innovations were computed for seven depth layers posited within the river as the differences between measured and simulated velocities. For each layer, the spatial correlation of velocity innovations was characterized by use of variogram analysis. Results were used with kriging to compute expected innovations within each layer at applicable model nodes. Expected innovations were added to simulated velocities to form integrated velocities, which were used with reverse particle tracking to identify the expected flow path near a sewage outfall as a function of flow depth.
Expected particle paths generated by use of the integrated velocities showed that surface velocities in the upper layers tended to originate nearer the Canadian shoreline than velocities near the channel bottom in the lower layers. Therefore, flow paths to U.S. public water intakes located on the river bottom are more likely to be in the United States than withdrawals near the water surface. Integrated velocities in the upper layers are generally consistent with the surface velocities indicated by drifting-buoy deployments. Information in the 2D hydrodynamic model and the ADCP measurements was insufficient to describe the vertical flow component. This limitation resulted in the inability to account for vertical movements on expected flow paths through Upper St. Clair River. A three dimensional hydrodynamic model would be needed to account for these effects.
Citation:
Holtschlag,
D.J., and Koschik, J.A., 2005, Augmenting two-dimensional hydrodynamic simulations
with measured velocity data to identify flow paths as a function of depth on Upper
St. Clair River in the Great Lakes Basin: Date Posted: June 15, 2005, U.S. Geological
Survey Scientific-Investigations Report 2005-5081. [https://pubs.water.usgs.gov/sir2005-5081/]
Contents
Abstract
Introduction
Purpose and Scope
Location
Previous Studies
Approach
Velocity Measurements in Upper St. Clair River
Hydrodynamic Simulation of Upper St. Clair River
Integration of Velocity Measurements With Flow Simulations
Results
Velocity Survey
Model Enhancements
Mesh Refinement
Bendway Correction
Peclet Number
Integration of Velocity Information with Hydrodynamic Simulations
Identification of Flow Path as a Function of Flow Depth
Summary and Conclusions
Acknowledgments
References Cited
Appendix 1 Summary of acoustic Doppler current profiler velocity data for transects on the
Upper St. Clair River
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For further information, contact:
Jim Nicholas, Director
U.S. Geological Survey
Michigan Water Science Center
6520 Mercantile Way, Suite 5
Lansing, MI 48911-5991
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