The water flow near Buckley, Washington, is scheduled to return to normal by Wednesday.
The work is being done on the diversion dam that pushes water and fish into the Corps of Engineers' fish facility. Migrating salmon are then moved upstream of the dam.
An estimated half a million pink salmon returned to the barrier dam in 2013. In addition to pink salmon, the barrier dam helps Chinook salmon, steelhead, bull trout and other species.