The main purpose of this study is to design, construct, and operate a physical hydraulic model of the Chicago River to analyze the occurrence of density currents in the Chicago River.
In November 1999, a noticeable difference in the color of the water between Lake Michigan and the Chicago River was observed by the Illinois Department of Natural Resources and later confirmed by the Metropolitan Water Reclamation District of Greater Chicago. This observation was supported by measurements performed by the USGS in 1998 that revealed a bi-directional flow in the Chicago River. This finding suggests that water of poorer quality might be flowing in the Chicago River that could have an adverse impact on Lake Michigan. Furthermore, the Chicago River has a higher use classification, thus high standards for water quality are required. A plausible explanation of this phenomenon is the potential occurrence of density currents during the winter months at the junction of the Chicago River with its North and South branches. This thesis is supported by the results from a three-dimensional hydrodynamic model (Bombardelli and Garcia, 2001).
The hydraulic model of the Chicago River will help us asses with more detail the conditions that lead to the development of density currents as well as their frequency and duration. Furthermore, preventive measures will be studied.
The physical model has a horizontal scale of 1 to 250 and a vertical scale of 1:20. This distortion is needed to have measurable flow depths in the laboratory. Scaling of flow and density gradients are achieved by maintaining the same densimetric Froude number in the model and prototype.
These movies show the evolution of a density current in the Chicago River from 1/7/2004 – 1/10/2004. The data is courtesy of the USGS Illinois Water Science Center.