The opening of the Morganza Spillway has relieved pressure on levees downriver, leading the Mississippi River to crest at Baton Rouge and New Orleans on Tuesday, sooner and at lower levels than had been predicted.

With the continuing release of water from the swollen Mississippi through the spillway, the river is now expected to top out at 45 feet in Baton Rouge, instead of at 47.5 feet, Ron Trumbla, a spokesman with the National Weather Service, said on Tuesday. Without the opening of the spillway, the river would have been at a record level, topping the mark of 47.3 feet set during the 1927 flood.

In New Orleans, the river crested Tuesday at about 17 feet, according to the National Weather Service.

While the massive diversion of water through the spillway seems to have spared Louisiana’s largest cities from widespread flooding, it is expected to mean the inundation of hundreds of thousands of acres of farmland and thousands of homes, as water from the spillway pours out into the Atchafalaya River basin. Evacuations have been taking place for days in the towns and communities throughout the basin, along with large-scale operations to protect these towns with sandbags and other barriers.