How the Panama Canal works: locks, Gatún Lake and what you see

The Panama Canal does not cut a flat trench between two seas. It lifts ships up to a lake, sails them across, and lowers them down the other side. The Panama Canal Authority puts the length at about 80 km between the Atlantic and Pacific oceans, and says the locks raise vessels from sea level to the level of Gatún Lake, 26 meters above the sea. Knowing that one fact makes every viewpoint in the Panama Canal visit guide easier to read. For the rest of the country, see the Panama guide.

See also the practical pages on the Miraflores Locks visit and on choosing between the canal experiences. The facts come from the canal authority's own pages and the Panama tourism authority.

The scale is worth a sentence. The canal operates 24 hours a day, 365 days a year, with about 9,000 workers, and between 13,000 and 14,000 ships use it each year according to the authority. That is traffic across every lock, day and night, which is why a single morning at one viewpoint shows only a sliver of it.

Follow a ship from the Pacific. It enters at the Pacific end and reaches the Miraflores locks, which lift it in two steps. It continues to Pedro Miguel, where one more step brings it to the level of Gatún Lake. The authority's FAQ describes the Atlantic side the other way round: Gatún has three levels, and Pedro Miguel and Miraflores share the Pacific side as one and two. Each set of locks is named for the town where it was built.

Between Pedro Miguel and the lake comes the Culebra Cut, the narrowest part of the canal. The authority says it runs from the north end of the Pedro Miguel locks to the south end of Gatún Lake at Gamboa, about 13.7 km, and was excavated through rock and limestone of the Central Cordillera. After the cut the ship crosses Gatún Lake, then reaches the Gatún locks, which lower it in three steps to the Atlantic.

That table is a map of the trip. If you only have a morning, Miraflores shows you the first step of that climb. If you have a day, adding the Caribbean side shows the descent and the newer locks. If you want the middle, the lake and the cut, a boat is the way to see them, and the tourism authority says partial crossing tours leave from the Causeway ports and from Gamboa.

A lock is a long chamber with gates at both ends. A ship enters, the gates close behind it, and water either flows in to lift the ship or drains out to lower it. When the level matches the next chamber, the gates ahead open and the ship moves on. The authority says the chambers of the original locks measure 304.8 meters long by about 33.5 meters wide.

The detail that surprises most visitors is the lack of pumps. The authority explains that the water used to raise and lower vessels comes from Gatún Lake by gravity: it is discharged into the locks through a main culvert system that extends below the chamber floors from the side walls and the central wall. Gravity does the lifting because the lake sits above the chambers. That is also why the lake level, and the rain that feeds it, matter so much to the whole operation.

For visitors, the cycle means each ship takes time. A vessel enters slowly, waits for the water to change, and leaves slowly. Plan to watch a whole passage rather than a few seconds of it, and use the film or exhibits at the visitor center while the chambers work. The pacing is also why the Miraflores article suggests checking the transit schedule before you go.

The canal added a third lane in the 2009 to 2016 expansion. The authority says the Cocolí and Agua Clara locks entered service on June 26, 2016, for Neopanamax vessels. Their chambers are much larger than the originals: 427 meters long, 55 meters wide and 18.3 meters deep, against 304.8 by about 33.5 for the Panamax locks at Miraflores, Pedro Miguel and Gatún.

Each new chamber has water-saving basins that can reuse up to 60 percent of the water in every lockage, according to the authority. The ships that use the new locks include container ships, liquefied petroleum gas and liquefied natural gas carriers, bulk carriers, vehicle carriers, tankers and cruise ships. Container vessels account for more than half of the transits through the expanded canal.

What does that mean at a viewpoint? Miraflores belongs to the original canal, so you see Panamax-size ships there. Agua Clara, on the Caribbean side, overlooks the newer, larger locks and the lake. If you care most about the biggest ships, the second site is the better match, which the comparison of canal experiences covers.

The canal's water comes from its watershed. The authority says the watershed is the main source of water for vessel transits and also provides 95 percent of the drinking water for the cities of Colón, Panama and San Miguelito. That dual role explains why the canal monitors rainfall closely, and why conditions can change the pace of traffic.

Read that carefully. It describes booking slots, not a count of every ship, and it is a temporary measure that can change. The practical effect for visitors is that a day at a viewpoint may show fewer ships than the yearly average suggests. Check the transit schedule on the canal's visitor site for your date, and read the original notice on the Panama Canal Authority page.

Seasons matter too. The UK government's safety advice says the Atlantic hurricane season runs from June to November, hurricanes do not directly affect Panama but often cause heavy rain, and October and November have the heaviest rainfall. A rain day is a practical issue for the viewing decks, not a reason to skip the canal, and the museum in the old town is the indoor backup.

At Miraflores, the Panama Canal's visitor site lists a ground-level terrace, bleachers on the first level and a viewing deck, along with exhibits and an IMAX film. You see the original chambers, the gates and ships being raised or lowered, and the tour is described as lasting about 1.5 hours.

At Agua Clara, the official description is a panoramic view with Gatún Lake on one side and the expansion works on the other, a projection room, a 1 km country trail and a 0.5 km ecological trail. The tour is listed at about 3 hours. The site is near Colón, about an hour's drive from the capital, so treat it as a separate outing.

On the water, a partial crossing takes you onto Gatún Lake and, depending on the tour, through part of the system. The tourism authority describes birds, monkeys and other wildlife along the way. The Amador Causeway, built in 1913 with rock excavated from the Culebra Cut, is a free walk with a view of ships waiting to enter the canal at the Pacific end.

If you are choosing where to put your time, think in terms of what you want to understand. Miraflores explains the lock. Agua Clara explains the expansion. The lake explains the water. The museum in Casco Antiguo explains the history.

Bring three questions with you. Which direction is the ship going, and which level is the chamber on? How big is the ship compared with the chamber? And where does the water come from? With the facts above you can answer all three without a guide, and a guide will make the answers richer.

Also keep your plan loose. Transits depend on the schedule, rainfall can change slot numbers, and weather can change the viewing. Build a buffer, check the official transit schedule, and book your tickets through the canal's own ticket pages. For a city base to pair with the canal, the Panama City guide covers where to stay and how to get around, and the tours and tickets guide covers buying from the source.

One mistake is expecting the canal to behave like a train timetable. Another is spending the whole visit in the film or exhibits and missing the ship. A third is arriving without checking the rainfall-driven changes in slots, then being surprised by a quiet chamber. A fourth is assuming Pedro Miguel and Gatún have visitor centers of their own, when the canal's visitor site lists Miraflores and Agua Clara as the two main ones.

Finally, do not forget the basics. Carry water and sun protection, use a ride-hailing app or a hotel-arranged car as the UK advice recommends for Panama's taxis, and check travel insurance and an eSIM before you fly so you can reach your driver and read the schedule on the day.