10-Year Water-Cycle Trend Identified in Wisconsin Lakes

A 10-year water-level cycle has been identified in Wisconsin's lakes, and researchers there were surprised to find that even the smallest lakes followed the same trend as gigantic lakes like Michigan and Huron.

"There was absolutely no reason for us to expect that our little lakes and lakes Michigan and Huron would act the same way, but they did," said Carl Watras, a research scientist with the Wisconsin Department of Natural Resources.

Wataras was part of a team of researchers the documented the 10-year water-level cycle in the region's lakes. The results are published in the journal Geophysical Research Letters.

The learned that, for at least the last 70 years, water levels in lakes would peak, then spend about 10 years on a downward trend before abruptly spiking again, only to repeat the decade-long decline again.

Though intriguingly, Watras said, the area's lakes seem to have recently broken from the script.

"The lakes [in our study] fell from 1998 all the way to 2010, meaning there was a roughly 12-year decline. And that should have been enough time for the oscillation to go through an up and a down, but it's just been down," he said in a statement from the University of Wisconsin-Madison.

Some lakes in northern Wisconsin, Watras learned, have dropped more than a meter and literally redefined the meaning of "waterfront property" for the many cottages on lake shores there.

A number of theories are in place as to why the water level in the area's lakes is bucking the trend and continuing to decline.

One is that the dredging of the St. Clair River increased the amount of water flowing out of Lake Huron and into Lake Erie. But Watras is suspicious of that theory.

"It's not what's causing low water," he said. "Low water is a region-wide, all-inclusive phenomenon. Like the jet stream, it's one of these atmospheric patterns that wiggles around."

A phenomenon called circumglobal teleconnection (CGT) is used to measure the pattern.

In the past 12 years, the GCT didn't wiggle much, which equated to less rainfall to fill the lakes. And warmer winters of late have led to less ice cover on the lakes , which further drove water levels down, the researcher explained.

"This may be a hiccup," Watras said. "Maybe it'll all go back up. Or maybe we'll go down and eventually reach a lower average water level. Or, maybe this oscillation changes and we get higher highs and lower lows. Frankly, our crystal ball doesn't let us look that far."

A lot of time and money has been spent on monitoring the Great Lakes' water levels, Watras said. But he noted that it costs far less to keep tabs on smaller bodies of water and, since the same hydrological cycle is affecting lakes both large and small, it might make more sense to spend less on monitoring small lakes and get the same results.

"[Our study] sure does speak well for long-term monitoring of small systems," Watras said.