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| Image courtesy Andrea Spallanzani via Pixabay |
The
Grand Canal that connects the River Shannon to Dublin is like a series
of steps of stairs, descending level by level as it makes its way to
Dublin. Locks on the canal allow barges to move from one level to
another, the locks filling with water to raise a barge or emptying to
lower it as it travels in the Dublin direction. Streams along the route
act as feeders for the canal, maintaining water level as it's lost and
moves from section to section when locks fill and empty (Pollardstown
Fen is one of the feeder sources for the Naas branch).
The Panama Canal
The
Panama Canal was a huge feat of engineering, construction starting in
1904 and finally completed in 1914. It allowed ships to travel from the
Pacific to the Atlantic, avoiding the long journey around South America
and having to negotiate the treacherous waters of Cape Horn at the
southernmost tip of Chile. It's similar in principle to the Grand Canal,
but incredibly more complex. The canal originally had a series of six
locks, three at each end. The locks are arranged in pairs, allowing
ships to travel in both directions at the same time. The Panama
Expansion Project has increased the number of locks to twelve. Ships
climb the canal through three locks at one end to reach Gatun Lake and
descend at the other end through another three locks to exit the canal.
Gatun Lake and the Chagres River are used for navigation over most of
the length of the canal, but the Pacific and Atlantic oceans are also at
different levels because of a variety of factors including tides,
atmospheric pressure and surges caused by storms. The locks compensate
for this difference in levels also, just like the way the locks on the
Grand Canal are necessary to cater for the River Shannon being at a
higher altitude above sea level than the exit of the canal near Dublin
Port.
This
episode of The Global Story on the BBC World Service from March of this
year examines how drought is threatening the canal and how it could
affect shipping.