Much of the central and eastern United States is experiencing extremely cold weather and sub-freezing temperatures that may form significant ice accumulations on the Upper Mississippi and Illinois Rivers.
The ice formations can restrict lock transit and narrow navigation channels. As a result of the freeze-up, river levels have dropped, especially at St. Louis, MO, where the river gage is forecast to drop from 2.0 feet on December 26 to -2.2 feet by January 4.
Gage height is a measurement of river elevation the U.S. Army Corps of Engineers (Corps) uses at various locations on individual rivers and refers to the number of feet above or below a reference point on the river bank. It does not refer to the depth of the river and varies by location.
The Corps, U.S. Coast Guard and river representatives have formed a joint committee that places restrictions (e.g., depth of draft for barges) on river traffic when the gage at St. Louis declines to -3.5 feet. In the event of possible extreme low water levels, the Corps has procedures to release water from upstream dams that have the potential to increase water levels.
