A new model of Lake Erie being developed by Ohio Sea Grant researcher Dr. Ethan Kubatko, Assistant Professor in the Department of Civil and Environmental Engineering and Geodetic Science at Ohio State University, may make it possible to one day predict water levels, water velocities, and other physical changes in the lake with greater accuracy.
Previous computer-based models used a structured grid made of equally sized squares that were so large-5 kilometers, or approximately the size of 55 football fields-they simply couldn’t accurately report shoreline details. Kubatko’s finite element grid employs a series of triangles that can vary in shape and size, effectively hugging the coast. Having higher resolution triangles as small as half a football field at the shore and larger ones in the deep water allows for more exact results.
"As you approach the coast, you start to encounter things like bays, inlets, man-made channels, and small tributaries, the geometry of which simply can’t be represented using elements that are as big as kilometers," Kubatko explains. "Smaller triangles also allow us to report more detailed flow patterns near the shore. Those currents are different than the middle of the lake, where the water flows more freely."
Kubatko started with the shoreline data and the topography of the lake bottom, each presented as a series of dots that must be connected by hand before the grid is then laid horizontally over the surface. Each corner of a grid triangle has a depth value attached to it, and the computer estimates the values of all the points in the middle and the way water behaves, whether it’s sloshing back and forth or raising and lowering.
The resulting map is a colorful illustration of Lake Erie, but there is still more work to be done. The next step is to take existing data from a small part of the lake, likely the Maumee Bay, and perform simulations to verify that the model is accurate. Such "reality checks" will allow Kubatko to compare data points and make adjustments if necessary, which should ultimately lead to a well-honed representation.
"The mapping of the lake is really the first component we need to predict not only large-scale water circulation patterns, but also to perform smaller, region-scale studies or even track the flow of pollutants in Lake Erie," Kubatko says.
To read more about this Ohio Sea Grant-funded research, visit http://ohioseagrant.osu.edu/_documents/twineline/v31i2.pdf