Panama Canal

Panama Canal, canal across the Isthmus of Panama, in Central America, that allows vessels to travel between the Pacific and Atlantic oceans. The waterway measures 64 km (40 mi), including dredged approach channels at each end. The Panama Canal handles a large volume of world shipping and enables vessels to avoid traveling around South America, reducing their voyages by thousands of miles and many days.

Panama Canal The Panama Canal consists of three separate canal locks, as well as other artificial waterways. The canal spans a total distance of 64 km (40 mi) from the Pacific Ocean to the Atlantic Ocean through the Isthmus of Panama. The ship shown here is entering the Panama Canal from the Caribbean, or Atlantic, side.Photo Researchers, Inc./Will and Deni McIntyre

The canal consists of artificially created lakes, channels, and a series of locks, or water filled chambers, that raise and lower ships through the mountainous terrain of central Panama. Built by the United States from 1904 to 1914, the Panama Canal posed major engineering challenges, such as damming a major river and digging a channel through a mountain ridge. It was the largest and most complex project of this kind ever undertaken at that time, employing tens of thousands of workers and costing $350 million.

The canal cuts through the central and most populated region of Panama, and it has been a point of dispute between the governments of Panama and the United States through most of its existence. Under a 1903 treaty, the United States controlled both the waterway and a large section of the surrounding land, known as the Panama Canal Zone, as if they were U.S. territory. Panamanians resented this arrangement and argued that their country was unfairly denied benefits from the canal. Eventually, riots and international pressure led the United States to negotiate two new treaties, which were signed in 1977 and took effect in 1979. The treaties recognized Panama’s ultimate ownership of the canal and all the surrounding lands. More than half of the former Canal Zone came under Panamanian control shortly after the treaties were ratified. Control of the canal was turned over to Panama on December 31, 1999.

The Miraflores Locks

Tugboats and electric trains guide large ships through the Miraflores Locks near the Pacific end of the

Panama Canal.

The canal consists of dredged approaches and three sets of locks at each end; Gatún Lake, of the largest artificially created bodies of water in the world; and the excavated portion of the crossing, called Gaillard Cut. At Gatún, on the Atlantic side, the locks form continuous steps; on the Pacific side, a small lake (Miraflores) separates the middle and upper locks.

Because the Isthmus of Panama extends east-west, a ship sailing from the Atlantic to the Pacific through the canal actually travels from northwest to southeast. To travel from the Atlantic to the Pacific, a ship enters Limón Bay from the north and anchors behind a breakwater to await scheduling of its passage. When ready, the canal authorities send out a canal pilot to take the vessel through the locks. The canal employs about 240 highly trained and experienced pilots to handle the complex job of steering ships through the waterway. As soon as the pilot takes over, the ship is under canal jurisdiction. Very large or hard-to-maneuver ships may require two or more pilots and assistance from tugboats.

The ship travels south-southeast about 11 km (7 mi) and enters the first lock at Gatún. Line handlers at the lock attach steel mooring cables that are controlled by powerful electric locomotives, called mules. The mules guide the ship through the locks and steady it while the chambers are filled with water. In three steps the ship is raised to the level of Gatún Lake, 26 m (85 ft) above the sea.

Panama Canal Cross Section

This cross section shows the route of a ship through the Panama Canal. From the Atlantic Ocean, a ship is raised 26 m (85 ft) through three sets of locks to the level of Gatún Lake. It travels through the lake and Gaillard Cut, the narrowest section of the canal. It is then lowered through a lock to Miraflores Lake, and passes through two more locks before reaching the Pacific Ocean.

The canal’s 12 locks (3 sets of double locks at each end) have the same dimensions: 33.5 m (110 ft) wide by 305 m (1,000 ft) long. The gates at each end are 2.1 m (7 ft) thick. Water enters and leaves each lock through a system of main culverts or pipes, which connect to 100 holes in the floor of each chamber. For each ship traveling through the canal, 197 million liters (52 million gallons) of fresh water are used, fed by gravity flow from Gatún Lake. To conserve water, smaller ships often go through the locks together.

At the top of the Gatún locks, the ship drops the mooring lines and proceeds under its own power for 37 km (23 mi) through the lake, following the former channel of the Chagres River. Gatún Dam, built adjoining the locks, flooded the river basin and formed the lake, which covers 430 sq km (166 sq mi). The flooding created a number of islands, as the water covered all but the tops of hills. One of these islands, Barro Colorado, is a wildlife refuge operated by the Smithsonian Tropical Research Institute.

The waterway gradually narrows until the river turns to the east at Gamboa, flowing under a bridge of the Panama Railroad. The canal’s marine division, with cranes, dredges, tugs, and barges, is located at Gamboa.

Lock A lock is a section of a waterway enclosed by gates at either end to allow ships to be raised or lowered to a different water level. In this example, a ship enters the upper level and the gates close behind it. The water is then allowed to drain into the lower level, lowering the water level of the lock and the ship. When the water level of the lock equals the level of the lower canal, the lower gates will open and the ship can proceed.

Lock

A lock is a section of a waterway enclosed by gates at either end to allow ships to be raised or lowered to

a different water level. In this example, a ship enters the upper level and the gates close behind it. The

water is then allowed to drain into the lower level, lowering the water level of the lock and the ship. When

the water level of the lock equals the level of the lower canal, the lower gates will open and the ship can

proceed.

South from Gamboa, the canal follows a channel dug through the mountains, which was the most difficult part of the construction project. Called Gaillard Cut, this section measures 14 km (9 mi) and traverses the Continental Divide, a ridge made of rock and shale. Numerous landslides occurred both during and after construction, requiring frequent dredging to keep the canal open. The channel through the cut is 150 m (500 ft) wide, the narrowest part of the canal. Originally only 91.5 m (300 ft), the cut was widened in phases beginning in the 1930s to allow two-way traffic. In the 1990s it was enlarged even more to accommodate larger ships.

At the southern end of Gaillard Cut, the ship slows and enters Pedro Miguel locks. Again, cables and mules guide and steady the ship before it is lowered 9.4 m (31 ft) to Miraflores Lake. The cables are released and the ship crosses the lake, which is 2.1 km (1.3 mi) long and lies 16 m (54 ft) above sea level. The ship then enters the last two locks, also named Miraflores, and is lowered to the level of the Pacific Ocean. The final stretch of the canal carries the ship to the harbor of Balboa, where the canal pilot leaves the vessel. The ship

sails under the Bridge of the Americas (formerly known as the Thatcher Ferry Bridge) and into the Bay of Panama, an arm of the Pacific Ocean. Northbound ships anchor in the Bay of Panama while waiting for their turn to travel through the canal to the Atlantic.

The entire trip through the canal takes between 8 and 10 hours plus waiting time. The canal operates 24 hours a day year-round. Each ship that travels through the canal pays a toll based on its capacity.

Boat Passing through Canal Lock

Canal locks are a series of gates designed to allow a boat or ship to pass from one level of water to another. Here, after a boat has entered the lock and all gates are secured, the downstream sluices open and water flows through them. When the water level is equal on either side of the downstream gate, water stops flowing through the sluices; the downstream gate opens, and the boat continues on at the new water level.

Canal construction consists chiefly of open cut excavation with ordinary power tools and construction machinery. The sides of the cut are often faced with masonry to prevent erosion of the banks by the wash of passing vessels and the subsequent blocking of the channel by a buildup of silt. Unlike roads and railways, canals cannot be made to conform to irregularities in terrain, but must consist of one or more level stretches, or reaches. Where reaches of different levels meet, vessels are transferred from one reach to the next usually by means of locks. A lock is a walled section of the channel, closed by water gates at both ends, in which the water level can be raised or lowered by means of valves or sluice ways to match the level in the upper or lower reach, as desired; when the levels are the same, the corresponding water gate is opened to permit a vessel to enter or leave the lock.

Other devices sometimes used to raise and lower small vessels are inclines and lifts. Inclines are paved or railed ramps over which vessels are hauled from one reach to the other by means of cables. In a lift the vessel is floated into a movable tank from one reach, water gates are closed, and the tank with the floating vessel is raised or lowered to the level of the next reach.

Locks, which are used in most multilevel canals, have certain disadvantages; frequently they are uneconomic because of the expense of construction and operation. Also, when traffic is heavy, the supply of water for the highest reach is difficult to maintain; in addition to the natural current flow, a lock full of water is lost from the upper reach in each locking operation. Consequently, to avoid construction of locks, canals are sometimes carried across depressions on embankments, over rivers on aqueducts, and through mountains in tunnels.