The Bonnet Carre Spillway is already turning parts of Lake Pontchartrain brown

(WVUE) - It did not take long for the rising Mississippi River to change the look of Lake Pontchartrain.

The U.S. Army Corps of Engineers began operating the Bonnet Carre Spillway Thursday, opening a handful of the structure's 350 bays.

Hours later, river water created mini waterfalls and whitewater rapids in parts of the 5.8 mile long spillway that runs between the river and the lake.

From the air, the big, muddy river moved into the brackish lake, mixing chocolate-colored, sediment-laden water with blue hues from the lake and the greens of vegetation.

However, it should be noted that for a couple of weeks river water has been pouring through gaps between the spillway pins, the large creosote timbers the Corps uses to close the bays.  Those flows had already flooded a portion of the spillway.

Nearly a century ago, engineers designed the gaps to relieve pressure from the river pushing up against the structure as it rises.

Many fishermen dread the opening of the spillway, which often damages crabs and other species.  Fertilizers in the river could lead to algae blooms in coming weeks, creating temporary dead zones in the lake.

The spillway's operation will prevent the Mississippi from rising above 17 feet at the Carrollton gauge in New Orleans, the technical flood stage.  Levees protect the city to 20 feet.