How do ships cross the Panama Canal's high ground?

Answer

Gatun Lake is the high point of the route.

Context

The Panama Canal does not run at sea level through the isthmus. Instead, ships climb to Gatun Lake and descend again on the other side. The Panama Canal Authority states that the locks raise ships 85 feet, or about 26 meters, to the lake surface. The original design has six pairs of chambers: three steps at Gatun on the Atlantic side, one at Pedro Miguel and two at Miraflores on the Pacific side, each chamber measuring 110 by 1,000 feet.

The lake was created by damming the Chagres River with the Gatun Dam, and the authority reports that it reached full height after the last spillway gate closed in June 1913. Using a lake avoided cutting a deep sea-level channel through the Continental Divide, which would have been far more costly and prone to landslides, and it provided a wide stretch of navigable water for part of the crossing.

The locks need no pumps. Gravity moves the water. To raise a ship, valves at the lower end close and valves at the upper end open, so water flows from the lake into the chamber through large culverts about 18 feet in diameter in the lock walls. To lower a ship, the process runs in reverse. Because the water comes from rainfall-fed Gatun Lake, droughts can limit operations, and the authority has studied ways to deepen the lake and conserve water. A common misconception is that the canal links the oceans at one level; in reality, the route is stepped, with the lake as its highest point.