The Persian Qanat, a UNESCO World Heritage

The Persian Qanat or Kariz (aqueduct) is an ancient water distribution system, which has been registered as a tangible Iranian cultural heritage on the UNESCO World Heritage List. Iranians were the first inventors of the aqueduct, But this method was later introduced to other countries from China to Morocco and America. The invention of the aqueduct can be described as the most significant contribution of Iranians in the field of water supply. This system can be traced back to at least 5 thousand years ago in Iran. The Kariz system is mostly found in the arid central regions, towards the east and southeast of Iran.

Some ancient Persian Qanat water supply systems in Iran are:

• The ancient Zavareh aqueduct, which some researchers believe dates back to 5 thousand years ago
• Gonabad aqueduct with a depth of 350 meters dating back 2500 years, is the deepest aqueduct in Iran
• The 40-kilometer aqueduct of the Tchogha Zanbil water treatment facility, which dates back to at least 3250 years ago
• The thousand-year-old water distribution network of Milan village, is located in east Azerbaijan province.

Since ancient times, the supply and salvage of water for drinking, irrigation, washing, etc., has been a vital factor in survival. That is why all the aqueducts, water reservoirs, yakhchāl (ice pit), water mills, water dams, bridges, and diversion dams were built.

Aqueduct building is the establishing facilities with the same percussive drilling method used to build mines, in which canals or waterways were used to extract water from groundwater reserves and transport it to the surface. The water would be transported from the mother well (where the water flows) into the aqueduct and to the surface outlet or the irrigation channel with the help of the earth’s gravity. The water transport route was a tunnel with a gentle slope.

Different Parts of the Persian Qanat

The Persian Qanat consists of several wells or vertical shafts on a sloping surface. Under these access shafts, there is a corridor called a waterway or groundwater reserve. In the following, we introduce the main parts of a Qanat:

• Channel: A channel or aqueduct tunnel is a horizontal channel that is dug to access the underground water reserve and its height is about 90 to 150 cm so that the aqueduct diggers can move around easily.
• Mazhar-e Qanat (Qanat Outlet): where the Qanat water leads, and it is the place where the Qanat channel is level with the sloping ground.
• Mileh Chah (Access Shaft): The access shafts are dug in the path of the aqueduct channel and their main use is to remove the excess soil from digging the channel and create proper ventilation in the path of the aqueduct. The access shafts are also used for dredging and necessary repairs along the Qanat channel. The diameter of the shafts is between 80 and 100 cm, and depending on the location of the aqueduct, the distance between them is 20 to 200 meters.
• Mother Well: It is the first well that is dug on the Qanat channel and the furthest well from the outlet. The mother well is dug deeper than the rest of the wells, and several blocked wells are dug in it in different directions to obtain more water flow in the aquifer.
• Khoshek Kar (Dry areas): parts of the aqueduct where water has not yet flowed after digging.
• Tareh Kar (Wet areas): The part of the aqueduct in which water flows.

Ancient Methods of Digging the Persian Qanat

By inventing the Qanat system, our ancestors were able to bring life to areas where it seemed impossible. We owe the start and continuation of life throughout many modern Iranian cities to this invention and their efforts in digging Persian Qanats.

The first step for the construction of any Qanat is to dig a borehole, which is done to test the presence of groundwater resources and determine the depth of the reserve. When the borehole is drilled and if water is found, they must determine whether the well will maintain a steady flow of water in an impermeable layer. If the answer is yes, the leveling and sloping of the aqueduct is the next step. Then the borehole is transformed into a mother well.

The waterway should not be too steep. Because in this case, the water flows at a high speed and causes the erosion of the Qanat channel walls, and as a result, the channel collapses. The work of digging the aqueduct usually starts from the Qanat outlet, That is, from where the water reaches the surface of the earth. Using shovels and picks, they dig a tunnel from the outlet towards the mother well. Sometimes, they start building the aqueduct channel from both sides at the same time.

Vertical access shafts are usually dug 20-35 meters apart from the ground surface to lead to the channel. Sometimes they dig the access shafts first and finally connect the wells by digging the channel. A mud or stone coating in the upper part of the wells makes them more reliable.

The excavated soil is transported to the surface of the earth with the help of a windlass using a bucket. If the well is too deep, they install another windlass in the middle of the shaft in a suitable place. Usually, a ring of soil accumulates on the ground around the well. If you look at the aqueduct from the sky, you will see a series of wells that look like a line with small openings.

The slope of the aqueduct is determined by using a hanging level between two ropes, each of which is 9 meters long. The slope of short aqueducts varies: from a slope decrease of 1 meter for every 1000 meters of length to a slope decrease of 1 meter for every 1500 meters of length. But the slope of long aqueducts is almost zero on a smaller scale.

When needed, they dig the aqueduct with a steeper slope. For this purpose, they usually destroy the routing line at one point and let the water reach a level lower than its original level and closer to the water table. Therefore, an underground waterfall is created. Realizing the flow of water in such places, people build water mills to use water for other purposes such as grinding grains.

Examples of the Persian Qanat in Iran

In the following, you can see pictures of Qanats from different areas in Iran and masterpiece examples of this Iranian architectural invention:

Disadvantages of the Aqueduct System

Although digging an aqueduct is a cheap and convenient way to provide water; It also has disadvantages:

• It is not possible to dig an aqueduct in lands that are flat and do not have a suitable slope, or whose soil is sandy and unstable
• Aqueducts are more vulnerable to floods and earthquakes than wells
• If the aqueduct is damaged, it may not be cost-effective to repair and rebuild it
• Aqueducts access shallow underground water tables and these resources shrink in the hot season of the year when crops need more irrigation, but the aqueduct may be dry or low on water.

Water Flow Rate of Persian Qanats

It should be noted that the water level of the aqueduct depends on various factors:

• Soil type
• The amount of groundwater exploitation in the region
• Oscillation of water table level
• The length and size of the aqueduct structure
• Aqueduct dredging

Aqueducts built on permanent water tables usually have constant water flow throughout the year. But when an aqueduct is located on an unstable or seasonal groundwater source or with permeable soil, its flow may be greatly reduced or run dry in summer or dry years. Therefore, the location of the aqueduct and its water supply table are important.

The water flow of some aqueducts reaches 1750 liters per minute, but most of the Persian Qanat systems have far less water flow, typically about 15 liters per minute.

Maintenance of the Qanat System

Each Qanat can access water for hundreds of years. Its wells also last between 20 and 50 years, of course, extended use depends on their timely restoration and proper care.

Aqueduct digging paths should be regularly dredged and repaired. Aqueducts are prone to collapse or damage due to sudden floods. To prevent the wells from being filled with soil, their openings are covered with stone slabs or other materials.

The people who are involved in digging the Qanat and maintaining this system are called Moqqani. They endure extreme work conditions in fulfilling such hard labor.

To check the ventilation of the underground channel, the Moqqani use castor oil lamps. If there isn’t enough oxygen to keep the flame burning, another well is dug. They clean mineral deposits from the bottom of the waterway. Any kind of damage to the well cannot be repaired without the help of these experts. This means users cannot access water until the aqueduct or water supply facilities are repaired.

These damages include the collapse of the roof of the waterway or the walls of the wells, the accumulation of sediments such as sand or mud in the underground channel, the blockage of the waterways, etc. It should be mentioned that the Moqqani in Yazd have always been famous for their professional skills in digging and maintaining the aqueduct.

Ownership and Water Distribution in Qanat Systems

Usually, there are several owners of the land where the Qanat is dug. As a result, Qanat water rights are bought and sold. Some landowners endow the Qanat on their land (partially and sometimes completely) to the community in which they live.

The distribution of Qanat water is determined by an agreement between its users or their representatives, divided into specific time intervals. If the irrigation levels of the aqueduct are desirable and significant and its users are numerous, the distribution is under the supervision of a trusted and known person, who is called “Mirab”. Mirab is someone who is chosen by the government or the Qanat stakeholders to monitor the fair distribution of water and is paid a certain salary.

The Importance of the Persian Qanat System

Without the digging of ancient aqueducts, many human settlements would never exist. Also, there were no large oases that later turned into small or big cities like Qazvin, Neyshabur, Kerman, Yazd, etc. As a result, there would be no farmlands in the mentioned areas.

Since ancient times, there have been rules on how to fairly distribute water between the various small and large villages along the Qanat channel. These rules were established to prevent any disagreement leading to disagreement, conflict, or disorder.

Even today, Persian Qanats are still important in some areas and remain the only source of residential water supply and irrigation. However, in densely populated areas, the Qanat has lost its effectiveness as the main source of water supply.

Finally, digging a Persian Qanat has been an essential and integral part of the life of ancient Iranians. It played an important role in the formation of many aspects of Iranian culture.

Zarch Qanat in Yazd

The oldest active Qanat in the world is called the Zarch Qanat which is over 3,000 years old. This aqueduct starts from Fahraj village and reaches Yazd through a 60-kilometer route, and after Yazd, it enters the Zarch region. Zarch aqueduct has three branches named Shirin, Shur and Ibrahim Khoydaki. Of course, currently, only the Shur branch is active and the other two branches are dry.

This aqueduct has about 2,000 access shafts, a few of which are located in the Jameh Mosque of Yazd. Since the aqueducts were built long before the arrival of Islam in Iran, it can be said that due to the importance of the water supply, the mosque was placed near the aqueduct access shafts. The wells were also used to fill the mosque’s water so that the worshipers had enough water for Wudu (ablution).

Until about 50 years ago, the water flow of the Zarch aqueduct was more than 180 liters per second, which has decreased significantly today. The Zarch Qanat is considered a national heritage that has been registered by UNESCO.

Frequently Asked Questions About the Persian Qanat

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