Figure 1: Lake Michigan circulation as simulated by the Princeton Ocean Model for the month of July, 1995. Note the strong near-shore currents. (Click on the image for a large version.)



Figure 2: Evolution of an initial contaminant field (circle)
over a 2 month period. Note the complex distribution
due to current structure.
(Click on the image for a large version.)


Figure 3: Different paths that contaminants can take
during the course of the year yet still arrive at the
Chicago city water intake.

Project Summary:
The Great Lakes represent the single most important source of fresh water to the contiguous United States. Given their large size, biological or chemical threat detection presents an enormous challenge.

Understanding transport within the Great Lake system is of vital importance to any threat detection scheme. In this pilot study, a version of the Princeton Ocean Model has been customized to simulate Lake Michigan’s three dimensional structure and circulation at a resolution of 4 by 4 Km in the horizontal and 100 m in the vertical (Figure 1).

In addition to these simulations we have performed studies modeling the spread of localized contaminants forward in time within the lake system (Figure 2), as well as the seasonal paths that contaminants could take to arrive at various important locations (Figure 3). These simulations reveal the complexity of contaminant transport in the lake.

At the same time the simulations identify locations in the lake from which contaminants will spread more effectively. These results can be used as a guide in designing a network of water quality sensors for early warnings on possible spreading of harmful contaminants introduced in the lake.

An extension of this study to include atmospheric forcings (by coupling the lake model with a mesoscale atmospheric model) will further improve the accuracy of our simulations.