Qanat

Qanat → The Ancient irrigation system found in Persia

“Kariz” or “Qanat” refers to an ancient method of water provision, regarded as one of Iran’s greatest contributions. This system channels water from underground tunnels to the surface for irrigation. Listed as a UNESCO heritage site, likely began around 4,000 years ago in the central deserts of Iran. Today, you can typically find this ancient irrigation system in central Iran, particularly in the east and southeast regions.

In addition to Qanat systems in desert towns, ancient Persia also featured water reservoirs, ice houses, water mills, dams, bridges, and diversion dams, other genius examples of the ancient Qanat system still in use in central Iran include Zavareh, Qasabeh in Gonbad, Choqa Zanbil, Milan Kariz in East Azerbaijan, and a 2,500-year-old underground canal on Kish Island in the Persian Gulf

What is Qanat and where is originates?

Qanat originally developed in ancient Persia, however, later, Arabs introduced it as an irrigation system through Arabia all the way toward North Africa, and later spread it across the Mediterranean region – they first brought it to North Africa and then to southern Spain through the Umayyad conquests and the associated transmission of scientific knowledge. In addition, Spanish went on to take the concept of transporting groundwater to fields and cities all the way to South America.

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Excavation & Construction of a Qanat Systems

Excavation ad digging for water and, to create a qanat typically involves a team of 3–4 muqannīs (Worker man). In the case of a shallow qanat, one worker is responsible for digging the horizontal shaft, another raises the excavated earth from the shaft, and a third distributes it at ground level.

The initial phase of constructing a Kariz involves sinking a trial shaft to check with the presence and ascertain the depth of the water down the ground canals. Once the trial shaft reaches the water, it is crucial to assess whether a consistent water flow exists within an impermeable stratum. If this condition is confirmed by diggers, the alignment and slope of the Kariz Qanat extending from the shaft need to be defined. This shaft then serves as the primary source of water, known as the mother well.

An Ancient type of water-supply system

In addition, the excavated canals should be moderate to prevent rapid water flow, which could lead to erosion of the walls and eventual collapse of the tunnel, typically, construction of a Qanat starts at the lower end, where the water is intended to surface. Using spikes and shovels, excavation of the tunnel commences towards the mother well. Occasionally, work begins simultaneously from both ends.

Drillers create vertical shafts from the surface to the tunnel approximately every 20 to 35 meters. Alternatively, they initially sink these shafts and then link them with a tunnel. Mud or stone linings reinforce these shafts at their upper sections.

The excavated soil is hoisted to the surface using a bucket and windlass. In cases where the shaft is particularly deep, a second windlass may be installed halfway down in a niche. Typically, a ring of soil accumulates around the shaft on the surface. Consequently, when viewed from above, sets of wells resemble a series of small craters in a line.

Establishing a Qanat System to flow the water

To establish the gradient of a Qanat System, use a spirit level suspended between two 9-meter-long cords. In shorter karizes, the gradient ranges from 1:1000 to 1:1500, whereas longer ones are nearly horizontal.

Sometimes, to increase the slope of a kariz route, workers divert the route at a specific point, allowing the water to flow to a lower level than before. Consequently, this creates an underground waterfall. Recognizing the potential water energy at these points, people constructed water mills to harness this energy for tasks such as grinding cereals.

The discharge of the water flow from the Qanat varies according to ground water level, 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 source a stable groundwater or is in porous soil, its flow may be reduced to virtually zero in summer, or in a dry year.

The flow of some Qanat in Iran may reach 1750 US gallons a minute, but that of the majority of kariz systems are much smaller, dropping to approximately 15 US gallons a minute.

What is the Qanat water management system?

People need to regularly clean and maintain the Qanat system and the excavated canals. They are subject to damage and destruction by flash floods. To prevent shafts from filling with sand, workers cover them with stone slabs.

The people involved in digging and maintaining Qanat system are called Moqannies. They suffer great inconvenience to perform their laborious jobs.

They carry castor-oil lamps to check the ventilation underground. If the air cannot keep the flame burning, they sink another shaft. They also clear the sediment deposited by minerals at the bottom of the aqueducts. In cases of damage, only these workers can fix the issues; without them, the kariz-water-supplied settlements would lose access to water.

Damages could be the falling in of the ceiling of aqueducts or walls on the shafts sides, the accumulation of sediments, sands or mud in the underground canals, the blockage of subterranean waterways, etc. It is worth notifying that the moqannies from Yazd city have always been famous for their skills to work professionally on qanat projects.

How To: Qanat’s water distribution?

Residents of the area where the Qanat system is located frequently own the land where they excavate it. Some land owners endow the Qanat routes in their lands partially or totally to the whole community living within it.

The Qanat underground system water’s distribution is based on time as determined by the users through their representatives. If the water flow is considerably high and users frequently access it, the water distribution must fall under the management of a trustworthy official known as a mirab. The joint users or the local government choose the mirab, who receives a fixed salary.

Existence of Qanat during the time

Without digging for water through the Kariz system, or Qanat, the human settlements in desert towns and oasis could not emerge. Some of the cities in Iran like Hamedan, Qazvin, Neyshabur, Kerman, Yazd are few examples of Qanat cities.

Since ancient times, there have been laws as to how to distribute water fairly among various small and large oasis on the underground tunnel routes to prevent any disagreements resulting in consequent disorder, clashes or disturbance.

However, Qanat system still remains to be the principal, and in some cases, the only source of irrigation and local water supply in many parts of Iran. But in the areas with more densely populated districts, water system has lost its importance as the main water provision source.

Map of countries with Qanats

During the Islamic period, this innovation spread to Muslim territories across North Africa, Southern Europe, and South Asia. Based on the fertile and weather conditions, each region developed distinct adaptations of the original aqueduct system tailored to their specific geological conditions.

The original term for Qanat in ancient Persia was the city of Kahan. During the Islamic era, the Arabic-derived term Qanat became widely use in different part of the world. In the Middle Eastern and African regions, people use various names for Qanat, including Falaj, Foggara, Khettara, and others. Qanat in Wikipedia