Lower Mississippi River

The Mississippi River is called the Lower Mississippi River from its confluence with the Ohio River to its mouth at the Gulf of Mexico.

Measured by water volume, the Lower Mississippi's primary branch is the Ohio River. At the confluence of the Ohio and the Middle Mississippi, the Ohio is the bigger river, with its long-term mean discharge at Cairo, Illinois being 281,500 cu ft/s (7,970 m³/s), while the long-term mean discharge of the Mississippi at Thebes, Illinois (just upriver from Cairo) is 208,200 cu ft/s (5,900 m³/s). Thus, by volume, the main branch of the Mississippi River system at Cairo can be considered to be the Ohio River (and the Allegheny River further upstream), rather than the Middle Mississippi.

In addition to the Ohio River, the major tributaries of the Lower Mississippi River are the White River, flowing in at the White River National Wildlife Refuge in east central Arkansas; the Arkansas River, joining the Mississippi at Arkansas Post; the Big Black River in Mississippi; the Yazoo River, meeting the Mississippi at Vicksburg, Mississippi; and the Red River in Louisiana.

The widest point of the Mississippi River is in the Lower Mississippi portion where it exceeds 1 mile (1.6 km) in width in several places.

Due to deliberate water diversion at the Old River Control Structure in Louisiana, the Atchafalaya River in Louisiana is now a major distributary of the Mississippi River, with 30% of the Mississippi's flow routinely entering the Gulf of Mexico by this route, rather than continuing down the Mississippi's current channel past Baton Rouge and New Orleans on a longer route to the Gulf.

Posted in: Names and Tributaries