Has a U.S. River Run Backwards Before?

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The ongoing drought conditions wreaking havoc across large swaths of the country have driven the water in Lake Michigan an inch below its previous record low, and aren’t stopping. Last month, the U.S. Army Corps of Engineers announced that, if this continues and the lake water drops below the level of the Chicago River, the river could reverse course and begin flowing back towards its source. (Thankfully, there’s a series of locks separating the two, which will help prevent the less-than-clean river from flowing into the lake and the city’s source of drinking water.) Has an American river ever done an about-face like this before?

Right Back Where it Started From

Oh yeah. In fact, the Chicago has done it before. If the river does reverse course, it won’t be running backwards so much as running forwards again.

When Europeans first settled in the Chicago area, the river drained into Lake Michigan, which was fine—except that settlers used the river to dump waste, and used the lake for drinking water. As the city grew, there were numerous outbreaks of typhoid and cholera because of contaminated drinking water, and something had to be done.

In the late 1800s, the city decided to solve their problem with an ambitious engineering feat: They would reverse the flow of the river and send it away from the lake and towards the Mississippi River. The so-called “Chicago Diversion” worked: It not only diverted contaminated water away from the city’s drinking water, but also connected the Great Lakes and Mississippi River water systems and opened up the possibility of commercial travel and trade between them.

It hasn't been just barges and haulers that could cross from one system to the other, though. Invasive Asian carp, introduced decades ago to southern fish farms as pond cleaners, have gradually made their way north, threatening native species and altering food webs as they go. With the fish nearing the Great Lakes, the idea of un-reversing (re-reversing?) the Chicago River has been kicked around, but now it looks like the river could take care of the problem itself. 

All Shook Up

The most famous of American Rivers, the mighty Mississippi, also might have gone backwards more than once. In 1811 and 1812, three earthquakes—the most powerful to ever hit the eastern U.S.—struck what was then a sparsely populated area of the Louisiana Territory. 

Eyewitness accounts from the quake read like Michael Bay scripts: The ground rippled and quivered; chasms opened up and swallowed livestock and wagons; sand and dirt exploded from the ground like volcanic eruptions and blotted out the sun; the Mississippi shook with such violence that the water ran backwards and boats were dragged upstream.

One boatman, wanting to get away from the trees falling over on the river banks, put his boat out into the middle of the river and soon found, he claimed, that “the current changed, and the boat hurried up, for about the space of a minute, with the velocity of the swiftest horse,” fast enough that he had to hold on to his hat to keep it on his head. 

Gradually, the man said, the river returned to its normal course. Exactly how long that took is unclear, and various firsthand accounts have the river going backwards for anywhere from a few hours to a few days. Whether the river even reversed itself at all is questionable, and the United States Geological Survey says that ground uplifts and waves moving upstream may have just created the illusion that the water was moving backwards. 

What’s more certain is that the Mississippi reversed course for about 24 hours when Hurricane Isaac struck last year, and when Hurricane Katrina hit in 2005.