Kariz (Qanat) is an ancient water provision technology inscribed in UNESCO’s List as an Iranian tangible cultural heritage. It can be described as the greatest contribution made by Iranians to hydraulics. This system must have been started at least 5000 years ago in Iran. The Kariz system is usually found in central Iran toward the east and southeast of Iran.
Some existing ancient examples of water provision in Iran are the old Zavareh kariz dating back to 5000 years ago, the 350m depth master well of Gonabad Qanat dating back to 2500 years ago, the 40km long aqueduct of Chogha Zanbil water refinery installation dating at least back to 3250 years ago and the 1000-year-old water distribution network of Milan village in East Azerbaijan province.
Therefore, since antiquity supplying and restoring water for drinking, irrigating, washing, etc have been an 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 from 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 drill a trial shaft (gamaneh) to prove its presence and determine the depth of the water table. When the trial shaft is drilled 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 have 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 drilled from the surface to the tunnel approximately every 20 – 35 m, or are drilled 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 routing 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 groundwater characteristics, the nature of the soil, and the 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 is much smaller, dropping to approximately 15 US liters a minute.
Maintenance of Qanats
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 drilled. They clear the deposited sediments formed by minerals at the bottom of the aqueducts. In any case 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 moqanies 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 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.
The 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 other 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.