Think you know a lot about the Mississippi River?

Think again.

Even after 183 years of working on the Mississippi River, the U.S. Army Corps of Engineers are still busy compiling data and making observations — especially during this significant moment in the river’s history.

With something as big and as powerful as the Mississippi River, the corps still wants to know more.

Inching ever closer to the second-highest recorded flood in Natchez, crews from the Vidalia office of the Corps of Engineers are venturing out into the river on almost a daily basis taking as many measurements as possible.

“During a historic flood like this it helps us to know more and more about the river,” Joe McFarland, head of operations and maintenance at the Vidalia office, said during a recent discussion about the flood.

“There is nothing set in stone about nature,” McFarland said. “As you know, information is power.”

So if the people who deal with the river on a daily basis are still trying to gain as much information as possible, the amount of misinformation spreading in the public must come as little surprise to McFarland and others whose careers are committed to the river.

On a normal day, few residents pause to think about the river unless they are enjoying a walk along the riverfront and bluffs.

When the waters start to rise all eyes turn to the river — and to the river gauge.

But what does that number you hear on your local radio station or see on the lit sign along the Vidalia riverfront mean?

Well, if you are like most residents, it is probably not what you think.

First, the river gauge does not indicate the depth of the river.

McFarland said this is probably the biggest misconception about the river.

The number on the river gauge actually has little to do with the depth of the river.

Zero on the gauge is not located on the riverbed.

Because the bottom of the river constantly changes over the course of time, the corps has set zero as a constant point in the river.

This is so that this year’s flood can be directly compared to the flood in 1927 and 1937 and any other daily measurement, even though the topography of the riverbed has changed.

So you might wonder then where zero is on the river gauge.

Zero on the river gauge is not set at sea level. In fact, zero on the river gauge in Natchez is not the same as the zero point in Vicksburg or even the zero point in St.Louis.

This one fact, leads to probably the second biggest misconception of the river.

The floor elevation of a building or road is not directly comparable to the river gauge level.

Zero on the Natchez river gauge is set at 17.28 feet above sea level.

So, to figure out how high the river is above sea level add 17.28. Thursday the river stood at 56.37 on the river gauge — which equals to 73.65 feet above sea level.

Earlier this week, I met a local at one of the Vidalia Riverfront’s businesses. As the waters were lapping onto the grass outside the back door, this local businesswoman expressed little concern about the flood. Her business sat at 78 feet above sea level. The river, she said was at 56 feet — nowhere close to reaching the building.

And while she probably has little to worry about, if she did the numbers she would discover that river was much closer than she thought.

Not enough to pack up her things yet.

But as McFarland said, “As you know, information is power.”

Ben Hillyer is the web editor of The Natchez Democrat. He can be reached at 601-445-3540 or by e-mail at ben.hillyer@natchezdemocrat.com