NEW ORLEANS – Recent heavy rains in the Midwest, combined with the last melting winter snows, will swell the Mississippi River to an expected crest at 16.5 feet in New Orleans by April 9, high enough to place local emergency officials on guard for potential river levee problems.

The crest will be about half a foot below the point designated as official flood stage at the Carrollton gauge in New Orleans, although a combination of levees and floodwalls protects the city to 20 feet at that location.

Hydrologists with the National Weather Service’s Lower Mississippi River Forecast Center in Slidell warned this week that, although no rain is forecast in the Mississippi and Ohio river valleys in the next few days, if heavy rains fall in that area during the next three weeks it could push the river even higher in New Orleans.

“Once it gets to 16 feet, we start getting a little worried,” said Bob Turner, regional executive director of the Southeast Louisiana Flood Protection Authority East.

The effects of high water actually begin when the river reaches 12.5 feet in New Orleans. That’s when water begins leaking between the wooden pins at the gate structure upriver at the Bonnet Carre Spillway, a channel between the Mississippi and Lake Pontchartrain that is opened to reduce pressure on levees downriver.

“The decision to open the Bonnet Carre Spillway is made at 17 feet,” said Turner, whose agency oversees levee operations in St. Bernard Parish, East Jefferson, and the east bank of Orleans Parish.

The forecast center expects the river to hit 15 feet at the Carrollton gauge on March 28.

“That’s assuming there’s no more bad weather, which could get us to that point sooner,” Turner said.