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Therefore, since
antiquity supplying and restoring water for drinking, irrigating, washing,
etc have been the essential issue for survival.
That is why all
those kariz systems, water reservoirs, icehouses, water mills, water dams,
bridges and diversion dams have been built.
Kariz is a mining
installation or technique using galleries or canals to extract water form
the depths of the earth to the ground. In fact, water is brought by
gravity flow from the upper end, where it seeps into the gallery to a
ground surface outlet and irrigation canal at its lower end. This is done
by means of a gently sloping tunnel.
Kariz Mining
Technique
The first step in
making a kariz is to sink a trial shaft (gamaneh) to prove the presence
and determine the depth of the water table. When the trial shaft is sunk
and water is reached, it must be determined if the well has struck a
constant flow of water in an impermeable stratum. If so the alignment and
slope of the kariz from the shaft has to be established. This shaft
becomes the mother well.
The gradient of the
gallery must not be too steep, because the water, then, will flow too fast
and erode the walls and the tunnel will fall in. Working on kariz making
usually begins at the lower end where its water is to come to the surface.
By spike and shovel, the tunnel starts to be dug back toward the mother
well. At times it begins simultaneously at both ends.
Vertical shafts are
sunk from the surface to the tunnel approximately every 20 - 35 m, or are
sunk first and then connected by a tunnel. Mud or stone linings at their
upper parts strengthen these shafts.
The soil excavated
is moved to the surface in a bucket by a windlass. If the shaft is too
deep a second windlass may be set halfway down in a niche. Usually there
accumulates a ring of soil around the shaft on the surface. So, looking
from the air, sets of wells look like a line of small craters.
The gradient of a
kariz is established by the use of a spirit level suspended between two
pieces of cord, each about 9 meters long. In a short kariz, the gradient
varies from 1:1000 to 1: 1500, but in a long one, it is nearly horizontal.
In some cases, when
kariz route slope needed to be steeper, they usually broke the route line
at one point and let water to another level lower than the original level.
Therefore, an underground waterfall was created. Knowing about the water
energy at such points, people built water mills to make use of the water
energy for other purposes like grinding cereals.
The discharge of the
water of kariz varies according to ground water characteristics, the
nature of the soil and season. Those that tap a permanent aquifer usually
have a constant flow throughout the year. If a kariz does not tap a stable
groundwater source or is in porous soil, its flow may be reduced to
virtually nothing in summer, or in a dry year. The flow of some kariz may
reach 1750 US liters a minute, but that of the majority of kariz systems
are much smaller, dropping to approximately 15 US liters a minute.
Maintenance
Kariz routes need to
be regularly cleaned and maintained: They are subject to damage and
destruction by flash floods. To prevent shafts from being filled with
sand, they are covered by stone slabs or other objects.
The people involved
in digging and maintaining kariz systems or qanats are called Moqannies.
They suffer great inconvenience to perform their laborious jobs.
They carry
castor-oil lamps to test the ventilation underground. If the air does not
keep the flame alight another shaft is sunk. They clear the deposited
sediments formed by minerals at the bottom of the aqueducts. At any cases
of incurred damages, nothing can be done without such people; meaning
water would not be accessible in the kariz-water-supplied settlements.
Damages could be the
falling in of the ceiling of aqueducts or walls of shafts, the
accumulation of sediments, sands or mud in the underground galleries, the
blockage of subterranean waterways, etc. It is worth notifying that the
moqannies from Yazd have always been famous for their skills to work
professionally on qanat projects.
Ownership &
Distribution of Water in Kariz Systems
Frequently the
ownership of the land where kariz is made in is in different hands and the
water is bought and sold. Some landlords endow the kariz routes in their
lands partially or totally to the whole community living within it.
The distribution of
the water of a kariz route is based on time as determined by the users
through their representatives. If the flow of a kariz is considerably high
and the users of the water are numerous, the distribution of the water has
to be under a trustworthy official known as mirab who is chosen by the
joint users or the government and is paid a certain salary.
Vitality of
Kariz Systems
Without kariz, many
human settlements could not emerge. Also there would be no oases to turn
later into large cities like Hamedan, Qazvin, Neyshabur, Kerman, Yazd and
a lot more smaller cities and towns. In the regions mentioned, there could
not be any piece of land cultivated either.
Since ancient times,
there have been laws as to how to distribute water fairly among various
small and large villages on the kariz routes to prevent any disagreements
resulting in consequent disorder, clashes or disturbance.
However, kariz still
remains to be the principal, and in some cases, the only source of
irrigation and domestic water supply in many parts of Iran. But in the
areas with more densely populated districts, kariz has lost its importance
as the main water provision source.
Finally, as an
essential and integral part of ancient Iranians? lives, kariz have played
a key role in forming many aspects of culture within the community.
Written By: Rahman
Mehraby |
