Little Goose Lock and Dam near Starbuck has been closed to river traffic because part of the gate must be replaced.
The lock is expected to be out of service until about May 1.
Small cracks were discovered in a metal arm of the gate in late spring 2013 and monitoring increased. But cracking worsened, and Monday the Corps of Engineers determined that the lock should remain closed until repairs are completed.
The closure could delay the transportation of juvenile fish past dams that was to begin in late April to comply with the 2014 Supplemental Biological Opinion.