High water on the Mississippi these days, owing to a very rainy winter and some relatively high temperatures up North keeping that precipitation from being of the frozen kind, and that water has to go somewhere.

So rather than it going into your back yard or your living room, the Army Corps of Engineers has decided to open the two major spillways on the lower end of the river it constructed years ago for just this purpose.

On Sunday, the Corps is opening the Bonnet Carre spillway in St. John The Baptist and St. Charles Parishes upriver from New Orleans. Doing so will insure that the river doesn’t flow more than 1.25 million cubic feet per second through the city, which keeps the levees along the river from taking too much pressure.

Opening Bonnet Carre will look like this – this is video from May 2011 when it was last opened…

And here’s another fairly interesting view from when it was last opened, this from passengers on a plane flying into Louis Armstrong International Airport while the spillway was open. You can see it makes for a wide spot in the river…

And on Tuesday, the Corps is set to open the Morganza Spillway in northern Point Coupee Parish, which unlike Bonnet Carre (this will be, if we’re not mistaken, the 10th time Bonnet Carre has been opened, which is uncommon but not completely rare) is almost never open. It was built in 1954 and has only been opened twice before.

But in May 2011, Morganza did open, and this is what it looked like…

And an aerial view from a helicopter…

Morganza is a bit more of a dicey thing than Bonnet Carre, because with the latter the water from the river just flows out into Lake Ponchartrain. That fact isn’t devoid of consequences, of course; fishing in the lake usually suffers from the influx of so much muddy fresh water. But insofar as it would affect human lives not involved in fishing, no so much. With Morganza it’s a different story…

But Col. Richard Hansen, head of the U.S. Army Corps of Engineers in New Orleans, cautioned St. Mary Parish residents that they could flood even if the spillway isn’t opened. Officials throughout Thursday said no final decision had been made whether or when to open the flood-control structure that diverts water from the Mississippi into the Atchafalaya River, but Hansen, during a night meeting in St. Martin Parish, said it could happen as early as Tuesday.

The Corps did announce that river levels would force the opening of the Bonnet Carre Spillway on Sunday, channeling the high water in the Mississippi into Lake Pontchartrain to relieve pressure on the levees in New Orleans.

Corps and parish officials said the Atchafalaya River, which flows between Morgan City and Berwick, could reach flood levels in a few weeks, especially if the Corps opens Morganza.

“Now is the time to take temporary flooding measures,” Hansen said before a crowd of more than 300 people at the Morgan City Auditorium, one of several flood-preparation meetings being held this week across south Louisiana.

The trigger for opening Morganza is that the river would be flowing at more than 1.5 million cubic feet per second. That is way too much water to ask the levees protecting Baton Rouge and parts downriver to hold back.

But the water flowing through Morganza goes into the Atchafalaya River, and there are folks living along its path. For example, Morgan City is near the Atchafalaya’s mouth, and when Morganza was last open here’s what that river looked like in Morgan City…

You’ll notice that the 2011 footage of the Morganza Spillway only showed a few bays open, rather than the whole thing, while Bonnet Carre had lots of bays open. That’s how the Corps regulates water flow – the more excess water that needs to be diverted, the more bays they open.

It’s a fascinating bit of civil engineering, and an interesting example of man’s triumph over the elements.