MORGANZA -- First it seeped, then it splashed, then it gurgled and now it sloshes -- the Mississippi River is pouring through one gate of the Morganza Spillway as it begins a destructive journey to the Gulf of Mexico via Morgan City miles to the south.

The Corps of Engineers about 3 p.m. Saturday raised the first gate of many that will eventually be opened to allow the swelling Mississippi to go where it really wants to go -- toward the Atchafalaya River and away from Baton Rouge and New Orleans.

Officials said gates of the spillway could be open for as long as three weeks as flood waters gathered from the nation's heartland make their way to Louisiana, which sits at the bottom of a massive funnel draining much of the nation.

In front of the stream coming through the spillway, wildlife will begin heading for higher ground, following human residents who have been preparing for more that a week for the flood, which could put as much as 25 feet of water in some parts of the spillway.

People remaining inside the spillway in south St. Landry Parish got mandatory evacuation notices Saturday afternoon.

This is only the second time the spillway has been put into use. The first was in 1973. Since then protective levees and seawalls have been raised in some places. Others remain at the water's mercy.

Before the stream reaches Morgan City it will test the mettle of flood protection measures at Krotz Springs, Stevensville and Butte La Rose.