The Granby Dam and Lock structure was constructed at the beginning of the 20th Century to provide at least a 4-foot navigation depth in the Congaree River up to the city of Columbia. Unused for many years, the structure remains in place as a short dam and an open-lock passage that is used by boaters to bypass the dam when river levels are low. A recent proposal to remove the Granby Dam has raised concerns that removing the dam might decrease water levels within the lock, making navigation through that area difficult, especially during periods of low river flow. This study examines how removing the dam would affect water levels and depths within the lock passage and in the river’s main channel.