Six of the port districts are located on the Columbia above the head of deep navigation, where barge traffic is composed principally of grain and petroleum downstream and cement and structural steel upstream.
They argued that the dams would improve navigation for barge traffic from interior regions to the ocean; provide a reliable source of irrigation for agricultural production; provide electricity for the World War II defense industry; and alleviate the flooding of downriver cities, as occurred in the 1948 destruction of Vanport City, Oregon.
The arrival of the Trent and Mersey Canal at Anderton in 1773 was detrimental to the salt trade at first, but ultimately beneficial, as salt was tipped down chutes from the canal into barges on the river navigation.
River navigation, apart from barge traffic on its lower course, almost completely disappeared after the coming of the railroads in the 1850s.
The river, shrunk by the summer's drought, has fallen to levels near the records set in 1988, putting a squeeze on river navigation that has required barge operators to run fewer barges at a time and to load them more lightly.
Locks and power dams make navigation possible for barges to Rome.
They are used to increase the amount of water available for generating hydroelectric power, to reduce peak discharge of floodwater created by large storms or heavy snowmelt, and to increase the depth of water in a river in order to improve navigation and allow barges and ships to travel more easily.
Both ports are located on the McClellan-Kerr Arkansas River Navigation System, which connects barge traffic from Tulsa and Muskogee to the Mississippi River via the Verdigris and Arkansas rivers, contributing to one of the busiest waterways in the world.
The canal has three barrages and four locks to control the flow and allow light navigation by some small barges.
Lake Chad is little used for commercial navigation, although there has been intermittent barge traffic between Bol and N'Djamena since the early 1950s.
