We woke up early to get to Miraflores locks Visitor Center when it was just opening to hopefully get to see a ship go through the locks. We arrived at the locks just shortly after they opened and were told that a ship was going through the locks. We rushed upstairs to the 4th floor observation deck just in time to see the ship go through the last set of locks at Miraflores and continue its journey towards the Atlantic Ocean. Luckily another ship, a cargo ship, was about to make its passage through the locks, so Bryan got his GoPro out and filmed it going through. Don’t worry…this video isn’t 30 minutes. We sped it up for you.
The idea to connect the Atlantic and Pacific Oceans with a 50-mile-long canal in Panama originated in the 1500’s. However, it wasn’t until the late 1800’s that this grand idea began it's arduous journey towards reality with the start of construction by the French. The project was abandoned by the French after several years of losing workers to diseases such as Yellow Fever and sloth-like progress of digging due to landslides triggered by the wet and tropical climate. They originally were going to build a sea level canal that would require significantly more excavation, but soon realized a lock canal would be more feasible to overcome the elevation difference between the oceans and the mountainous middle section of the canal. After the French abandoned the project, years later the US picked up the reins and restarted construction in 1904. A genius solution to dramatically reduce the amount of excavation needed was the damning of the Chagres river to create the artificial lake Gatun. By creating the lake, minimal excavation was needed for a significant length of the canal. Still, an approximate total of 268 million cubic yards of material was excavated of the duration of the project. In 1914 the canal opened.
To give you a better visual of what we described above, directly below is an elevation view of what the isthmus looked like before construction. As you can see there was quite an elevation difference between the sea-level of the Atlantic and Pacific oceans and mountainous Culebra area (~210 feet at peak). Instead of leveling out the entire 50-mile stretch, Culebra was cut from 210 feet down to 39 feet above mean sea level. The Chagres river was then dammed, creating the artificial Lake Gatun and raising the waterway passage to 85 feet above sea level (allowing for adequate water depth for the ships to pass). As you can see, ships entering the canal from either ocean are raised by the locks to the level of Lake Gatun (whose water is consistently recharged by the inflow of the Chagres River) and then lowered back down to the other side.
While standing there we contemplated the head loss effects on the filling of the lock and discussed the fluid mechanics of it because that’s what engineers do! As we were filming the ship go through, tons of people filled the observation deck and it quickly became quite crowded. Our recommendation is to arrive there early to beat the crowds, plus the ships only go through in the morning and evening so you must time it right for your best chance to see a ship. We next went through the rest of the visitor’s center, watched a video on the history of the canal, and went through the 4-level museum explaining the history of the canal and how it was built. While it was all very interesting and well organized, we (engineers) left with many unanswered questions.
In 2016, a new set of larger locks were added to allow the larger modern ships to pass through the canal. These expanded locks include water-saving basins that reuse 60% of Lake Gatun’s water, which is about 7% more efficient than the existing locks system. The museum didn’t really explain where the 7% efficiency comes from, but we figure it works like this:
Say a ship is coming from Lake Gatun traveling towards to the Pacific Ocean. There is a series of 3 locks (think of these like stair steps) the ship has to go through to get lowered to the level of the Pacific Ocean.
Beside each of these 3 locks are 3 enormous basins. Enormous as in each basin is the size of 25 Olympic swimming pools. The ship enters the first lock and prepares to get lowered to the 2nd lock. In the old locks, the water would just continue to flow into the lower lock until the water levels become even. The lock doors would open and the ship would pass into the lower lock. The process would then repeat itself. When the ship is in the last lock getting lowered to the Pacific, the water from Lake Gatun would just merely flow into the Pacific Ocean. With the new locks, water from Lake Gatun fills the water saving basins as well as the lower lock. This way, when the lock needs to be filled again, it can reuse the water from the basin rather than more water from Gatun Lake.
The 3 basins have varied bottom elevations which is a clever design to us after reflecting on what we saw during the operation of the original lock system. We think these basins most likely to allow the locks to fill and raise/lower the ships at a more uniform rate.
While watching the old lock system fill we noticed (and you may in the video) the ships would raise quickly at first in each lock, but the water filling the lock would slow down significantly as the ship began to reach the highest level (equilibrium with the next lock). Before explaining how we think the new lock system functions it is important we first explain why the filling of the lock and raising of the ship slows down in the original lock system. Remember that the locks raise the ships from seal level up the elevation of the artificial lake Gatun which is 85 feet above sea level. This difference in elevation of the water levels is how the locks fill. From what we read in the museum and online, absolutely no pumps are used in the original or new lock systems, so everything works by gravity. Water flows from the lake through culverts (really big pipes) to fill the locks and raise the ships. In simple terms the greater the elevation difference is between the water level of the lock and the source of the water (either the next lock or the lake), the faster the lock will fill. So as the lock begins to fill up the elevation difference between the water levels decreases and that is why the ships raised quickly at first and then very slowly at the end.
Now back to the new lock system with the 3 water saving basins per lock. We noticed these basins are built at increasing elevations relative to one another (see picture above numbers 1-3) which we believe was done purposefully to maintain a more consistent elevation difference as the lock raises/lowers. The lowest basin most likely fills the lock first, and as the water levels near equilibrium.....boom the middle basin then kicks in to "reset" the elevation difference and continue to fill the lock, and then so on for the highest basin.
To say the least, we really found the new canal expansion interesting. If you’re interested in the new locks, they do have a visitor’s center on the Atlantic side (named Agua Clara). It apparently has a panoramic view of the locks and Gatun Lake.