Today, we talk about qanats. (Betcha don't know
what a qanat is!) The University of Houston's
College of Engineering presents this series about
the machines that make our civilization run, and
the people whose ingenuity created them.
Jakob Bronowski included an
eerie scene in his Ascent of Man
series on TV. It's in his program on the origins of
agriculture. It's a desert scene. An Arab woman
passes through an entryway in the sand. She walks
down, down, into the earth. Far under the surface
she draws water from a long subterranean canal hewn
through rock. The canal runs for miles. An aerial
photo shows access shafts, a hundred feet apart,
running down to the canal far below.
Geographer Dale Lightfoot writes about those
watercourses. They're called qanats and they are
remarkable constructions. The oldest ones we know
about were built in Persia some 2700 years ago.
Qanats were built throughout the fertile crescent.
Then, when Islam spread Arab culture to the west in
the 8th century, qanat building followed all the
way to Spain, and beyond.
Qanats run under sloping ground. At the high end, a
vertical mother shaft is dug down into an aquifer.
A horizontal tunnel carries water away from the
aquifer to the spot, maybe one mile away, maybe 40,
where the tunnel meets the surface of the land.
There, water emerges to irrigate low-lying farm
lands. The access shafts let people lower
themselves to the main tunnel in baskets. There
they can draw water, or they can clear trash from
the tunnel.
With all our pumps and power supplies, we have
trouble understanding qanats. If we want ground
water, we drill into an aquifer, pump the water
out, and distribute it in pipes. But that wasn't
possible until a few hundred years ago. While
qanats take a vast investment of labor, once
they're built they last until either the aquifer
dries up or civilization forgets they're there.
Local people cut these vast tunnels through
limestone and dense alluvial soil. The Romans
weren't very inventive; but they fancied great
engineering works. So they did a lot of qanat
building after they conquered Syria. The irony of
that is, modern Syrians speak of Roman qanats when
they aren't a Roman idea at all. In any case, some
239 qanats are scattered through Syria alone.
The depth of those old water courses was anywhere
from 30 to as much as 300 feet at the mother shaft,
depending on the rainfall and the geology of the
aquifer. The underground canals were typically five
feet in height. With all that digging, these
projects take their place right along with the
ancient wonders of the world.
Water is a primal theme in the dry Middle East.
Fountains recur in Arab architecture and Arab
literature. The action of the Old Testament also
moves from one spring or well to the next, and the
sacramental importance of water is apparent from
the beginning. Once we learn about these
astonishing tunnels, we realize we've found much
more than remarkable works of engineering. We have,
in fact, found the very soul of an ancient people.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
Lightfoot, D. R., QANATS in the Levant: Hydraulic
Technology at the Periphery of Early Empires.
Technology and Culture, Vol. 38, No. 2,
April 1997, pp. 451.
Bronowski, J., The Ascent of Man.
Boston: Little, Brown and Company, 1973, Chapter 2,
The Harvest of the Seasons. (This is also available
on videotape and film.)
I am grateful to Dale Lightfoot, Oklahoma State
University Department of Geography, for his counsel
on this episode.
The Engines of Our Ingenuity is
Copyright © 1988-1997 by John H.
Lienhard.
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