Scientists may have just solved the mystery of Minnesota’s vanishing river.

Beyond Grand Marais, the Brule River splits at the Devil’s Kettle waterfall. Half of it tumbles down and continues on its way. The rest pours into a dark deep hole in the hill ... and disappears.

For years, people have tried to figure out where that water goes. Logs and Ping-Pong balls tossed into the churning cauldron seemed to simply vanish, fueling speculation that the lost branch of the river might flow for miles underground, carrying bobbing debris down to the distant shores of Lake Superior or off to some underground cavern.

Now, finally, a researcher from the Minnesota Department of Natural Resources (DNR) thinks he’s cracked the riddle of Devil’s Kettle.

“It’s a beautiful optical illusion,” said DNR mapping hydrologist Jeff Green, who first marveled at the wandering waterway during a family trip to Judge C.R. Magney State Park years ago.

The disappearing half of the river, it turns out, reappears pretty quickly downstream.

Green and a team of DNR hydrologists used stream gauging equipment to measure the volume of water flowing above the falls and below. The results were virtually identical, which meant half the river wasn’t dribbling into the center of the earth or flowing underground to rejoin Lake Superior.

Above the falls, the river flowed at 123 cubic feet per second. Several hundred feet below Devil’s Kettle, the flow was still 121 feet per second. In the world of stream gauging, Green explained, those readings are nearly identical. The river didn’t go anywhere.

“It made my day, when we found this,” said Green, who has spent his career studying and safeguarding water sources in southern Minnesota. “Science has been getting kind of a bad rap lately. … This is an example of applying science. It works, and that’s why we do it.”

Green and University of Minnesota researcher Calvin Alexander plan to test their findings by pouring vegetable-based dye into the pothole under the falls later this year, when the Brule is running low. The fluorescent, biodegradable dye is highly visible and won’t be easily diluted, even by a waterfall, so the hydrologists plan to use only a few quarts of the DayGlo dye.

So if the river didn’t stray far, why didn’t the Ping-Pong balls and other debris resurface downriver?

Alexander has a theory.

“The plunge pool below the Kettle is an unbelievably powerful system of recirculating currents, capable of disintegrating material and holding it under water until it resurfaces at some point downstream,” he said in a DNR statement.

But while the swirling waters might capture Ping-Pong balls and logs, thrashing them around like a washing machine, the dye molecules won’t be held in Devil’s Kettle and should be visible downriver to confirm Green’s theory.

No word on whether the DNR will tackle the mystery of Bigfoot next.