THE LAND BRIDGES GET MORE OF A WORKOUT.

It's not enough that Iranian proxies and African pirates are scaring shippers away from Suez, which makes for intermodal business on Eurasian railways.  Now, the rains aren't coming in Central America, and transloading in Panama has picked up.

In an advisory to its customers, shipping giant Maersk said it will use trains to avoid the drought-plagued Panama Canal for some of its container traffic.

The Canal Authority recently reduced the number and weight of vessels that can pass through the canal based on current and projected water levels in Gatun Lake, the rainfall-fed principal reservoir that floats ships through the canal’s lock system, Maersk said. That means some containers will be transported across the isthmus by the Panama Canal Railway.

The railroad has long had that capability, in order to cater to container ships too large to transit the canal.  The canal has since been widened, and although the new locks conserve water relative to the original, still operating locks, a transit still uses a lot of water.  David McCullough describes the water requirements for one transit of the original, some 52 million gallons of water, as "a day's water use for a major city."  All that fresh water goes to the oceans.

There were good reasons to build the canal in the form it took.  Because of differences in tides at sea level, and the presence of a backbone ridge defining a continental divide, a sea-level canal was impracticable, and as laid out, the canal replaced the Rio Grande from the Pacific Ocean at Panama City to the continental divide, with the Gaillard Cut at the ridge.  The builders dammed the Chagres River to create Gatun Lake, and even that proved inadequate to store water, with an additional reservoir, Madden Lake, completed in 1935.  As the main channel transits Gatun Lake, there are two challenges to canal operation: maintaining that pressure head for the locks, and keeping the channel deep enough for those larger ships.

Look for container traffic diversion to the other land bridges, including the North American railroads serving Mexico, the States, and Canada.