Plans to open a Mississippi River spillway in Louisiana for the third time ever have been put off for four days because the river’s rising more slowly than expected.

The Army Corps of Engineers said in a news release Thursday that it wants to open the Morganza Spillway only when it becomes necessary. The delay will avoid putting additional water into the Atchafalaya Basin.

The opening had been planned Sunday, but is now planned for Thursday, June 6.

Any opening this year would be the second time the structure has been used to control floodwaters.

Morganza was opened in 2011 for flood control. In 1973, it was used to protect an upriver structure that keeps the Atchafalaya River from capturing the Mississippi.