In the 19th century, navigation on the Canal was simple because on an artificial waterway boaters only had to stay within the canal's banks and travel either west or east. In the 20th century, the Barge Canal returned to natural waterways such as the Mohawk and Seneca Rivers and Oneida Lake, where channels were cut through rivers and lakes to provide accurate depth and width. Buoys marked those channels, and their lamps had to be refueled and cleaned daily because for much of the 20th century the canal operated day and night. The buoys were color coded and numbered, keyed to charts that let boaters know their exact location.