The Army Corps of Engineers plans to cut the flow of water coming out of Gavins Point Dam in southeast South Dakota next week to check for damage from last year's flooding.
The corps said Friday it will conduct the test on Tuesday to look for damage caused by last summer's sustained high water releases.
People who live downstream from the dam in Nebraska and Iowa could see the Missouri River drop more than a foot on Tuesday because of the test.
The corps' John Remus says preliminary inspections indicated the dam sustained minor damage to its spillway, so officials want to get a better look.
If the test is successful, officials will plan to reduce the flow for a longer period in May to complete damage assessments.