Panama Canal: Locks, the Gaillard Cut and the Rainforest Railway

A cargo ship stacked high with containers glides into a concrete chamber, the gates close behind it, and the water beneath it begins to rise. The Panama Canal locks lift ships 26 metres over the isthmus and lower them again on the far side, and they have done so every day since 1914, with no pumps and almost no change to the principle on which they were built. This guide explains how the Panama Canal locks work, what lies between them, where to watch the ships and how the railway beside the canal fits in, and it notes where the canal features on our Journey through Central America: Panama, Costa Rica, Honduras, and Guatemala.

Why the canal needs locks

The Isthmus of Panama is narrow, but it is not flat. A ridge of hills, the Continental Divide, runs along it, and the early French plan of 1881, a sea-level canal like the one at Suez, collapsed under engineering problems and heavy loss of life. The United States took over the project in 1904 and chose a different design: dam the Chagres River to make an enormous lake, Gatun Lake, 26 metres above sea level; lift ships up to it and down from it by locks; and cut a channel through the highest ground. The canal opened on 15 August 1914, when the steamer Ancon completed the first transit.

The lake solves two problems at once. It supplies the fresh water that fills the locks, and it replaces many kilometres of excavation with a stretch of open water. The shape of the isthmus also produces a small surprise: because Panama curves in an S, the Pacific end of the canal lies to the east of the Atlantic end, the reverse of what most people expect. Today the lake forms a large part of the route across the isthmus, and ships spend much of a crossing sailing among forested islands rather than through a man-made trench.

How the Panama Canal locks work

Each lock is a series of concrete chambers closed by pairs of huge steel gates. A ship enters a chamber, the gates close behind it, and water either flows in to raise the ship or drains out to lower it. All of this is done by gravity: water moves through large culverts in the walls and floor, controlled by valves, and no pumps are used. The gates can only be opened when the water level on both sides is equal, which is why the process is steady rather than dramatic. When the chamber is full, the ship is level with the next one and the gates ahead open.

Ships do not move under their own power through the chambers. Electric locomotives run on rails along the lock walls, and steel cables from the locomotives hold the ship centred and steady as it moves forward, because the original chambers are only about 33.5 metres wide and large ships pass with very little room to spare. The locks come in pairs, so that traffic can pass in both directions at once.

The three sets of Panama Canal locks

There are three lock complexes on the original canal. On the Atlantic side, the Gatun Locks lift ships in three steps from sea level to Gatun Lake. On the Pacific side, the Pedro Miguel Locks lower ships by one step, about 9 metres, to Miraflores Lake, and the Miraflores Locks, a short distance beyond, lower them in two steps to the Pacific. Miraflores Lake sits at about 16.5 metres above sea level, and the whole system raises or lowers a ship by 26 metres in total.

The canal was widened in 2016 with a third lane of larger locks, Agua Clara on the Atlantic side and Cocoli on the Pacific side, each with three chambers and basins that save water, which allow much larger New Panamax ships to pass. The original locks are still in use, and watching a ship enter the older, narrower chambers is a good way to see how the whole system was designed.

Watching the locks at Miraflores

The Miraflores Locks, not far from Panama City, are a popular place to see the canal at work from the shore, and they are close to the city. A visitor centre overlooks the chambers, and there are viewing platforms from which to watch ships enter, rise or fall and leave. Opening hours and ticketing change, so check the official website before you plan a visit around a particular crossing.

West of the Miraflores Locks, the Pacific entrance to the canal is crossed by the Bridge of the Americas, a steel arch bridge, and the skyline of Panama City rises on the eastern shore. The Pedro Miguel Locks lie a short distance further along the canal, and they are usually seen from the water rather than from land. On the Atlantic side, the Agua Clara visitor centre overlooks the new, larger locks.

The Gaillard Cut: through the Continental Divide

North of the Pedro Miguel Locks, the canal runs through the Gaillard Cut, a channel about 13 kilometres long that cuts through the Continental Divide as far as Gamboa. It was known during construction as the Culebra Cut, and in 1915 it was renamed for David du Bose Gaillard, the US Army engineer who directed the excavation. The average depth of the channel is about 13 metres, and landslides on the slopes were a persistent problem during construction. The Centennial Bridge, a cable-stayed road bridge, crosses the canal near the southern end of the cut.

Seen from a ship, the cut is a strange landscape: a long, narrow channel with steep, stepped sides and forest all the way up, with large ships sliding through it very slowly. It shows clearly how much earth had to be moved to make the canal.

Gatun Lake and Gamboa

At Gamboa the canal meets the Chagres River and opens out into Gatun Lake. The channel through the lake runs for about 37 kilometres, in water between roughly 14 and 26 metres deep, and the shores are covered in rainforest, with islands that were once hilltops. When the lake was flooded, large areas of forest were drowned, and dead tree trunks still stand in the shallows in places.

The Panama Railroad: the rainforest railway

The canal was not the first link between the oceans. The Panama Railroad was built across the isthmus between 1850 and 1855 and was an instant success, carrying passengers and cargo between the Atlantic and the Pacific long before the canal opened. Its route and infrastructure helped to make Panama the natural place for the canal, and the railway still runs today, mostly alongside the canal, between Panama City and the Atlantic port of Colón. A journey on it passes through rainforest, and it makes a fitting counterpart to a day on the water.

How long does a Panama Canal transit take?

A full transit takes most of a day, commonly eight to ten hours including waiting time. The lock operations themselves are only a part of it, because the ship also has to cross the lake and the cut, and many vessels wait their turn at anchor before they enter. Visitors on excursions usually make a partial transit, which covers one section of the canal and takes a few hours.

What is the difference between a full and a partial transit?

A full transit crosses the whole canal between the Pacific and the Atlantic, while a partial transit covers only one section and then returns by road or rail. On Day 4 of our tour, for example, the group sails through the Miraflores and Pedro Miguel Locks and the Gaillard Cut, and leaves the boat at Gamboa, rather than going on to the Atlantic locks.

Can you see the Panama Canal locks without a boat?

Yes: the viewing platforms at Miraflores on the Pacific side and Agua Clara on the Atlantic side let you watch ships being raised or lowered without boarding anything. Miraflores shows the original, narrower chambers and is the easier choice from Panama City, while Agua Clara shows the larger locks built in 2016. A boat is the way to experience a lock from inside, but the shore gives a clearer view of how the system works.

When is the best time to visit the Panama Canal?

The canal works all year, but the weather changes. Panama’s dry season runs roughly from December to April, with clearer skies and less rain, which makes the shore viewpoints and the Gaillard Cut easier to see. From May to November the rains arrive, usually as afternoon showers, and the forest turns deeper green, so a light waterproof jacket is a sensible addition at any time of year.

Seeing the canal with a small group

If you would rather see the canal with a small group, the first days of our 27-day Central America journey are spent in Panama City. On Day 2 the group tours the old quarter of Casco Viejo and visits the Miraflores Locks to see the canal, Day 3 is a cultural visit to an Emberá community, and Day 4 is the boat voyage through the locks and the Gaillard Cut to Gamboa, an overland journey to Colón and the return to Panama City on the Panama Canal Railway. Our guide to Panama City, Panama describes the city around it. A Tour Specialist can talk you through the days before you book.

The group then flies on to Costa Rica, where it reaches the rainforest and volcano country around La Fortuna. Our guide to the whole route shows where the canal fits in the journey. The group is small, with up to 16 travellers, and solo travellers are welcome. However you see the canal, give it time: watch one ship through a lock from start to finish, and the whole enterprise starts to make sense.