Navigation was the Corps of Engineers' earliest Civil Works mission, dating to Federal laws in 1824 authorizing and funding the Corps to improve safety on the Ohio and Mississippi Rivers and several ports. The Corps provides safe, reliable, efficient, and environmentally sustainable waterborne transportation systems (channels, harbors, and waterways) for movement of commerce, national security needs, and recreation.
What is a lock and dam system?
Major water transportation routes such as the Panama Canal and much of the navigable portion of the Mississippi River system are made possible by a series of locks and dams.
The dams form lakes, called navigation pools, behind them. Most pools in the United States are maintained at a constant minimum water depth of nine feet for safe navigation. Locks at each of the dams provide a passageway through the dam and more generally allow vessels to move through bodies of water that are at different water heights.
Why are lock and dams necessary for navigation?
Rivers often experience significant changes in water depth depending upon rainfall in their watersheds. Pools behind the dams provide reliable water depths for modern towboats pushing barges loaded with cargo.
Using locks and dams, massive ships can navigate through shallow or steep sections of river, traveling much further than natural terrain would allow.
Locks and dams can also be used to link waterways separated by natural divides. The Panama Canal is a good example. Vessels entering the Canal system at sea level on the Pacific side are stair-stepped through a series of locks to waterways at higher elevations, before being stepped through a series of locks back down to sea-level on the Atlantic side.
How does a lock work?
Boat locks work as a sort of "water elevator" to raise ships to higher or lower elevations. This is necessary to help big and heavy boats get through shallow or steep river areas.
A lock is a big chamber that sits in the water. It has rigid sidewalls and moveable gates at each end that can be opened to allow a vessel into the chamber and then closed once the vessel is on the chamber.
For a ship going downstream, the lock is filled with water by opening the filling valve. Then the drain valve and upstream and downstream gates are closed so the chamber water level rises to the upstream level. Then the upstream gate opens and the boat moves in. To lower the boat, the gates are closed behind it, the filling valve is closed, and the drain valve is opened.
The higher water in the lock chamber drains to the downstream level in a few minutes. Then, the downstream gate is opened and the boat moves out on the lower water level. The process is reversed for a boat going upstream.