Most rivers in Iran are seasonal and have traditionally not been able to supply the needs of urban settlements. Major rivers like the Arvand, Aras, Zayandeh, Sefid and Atrak were few and far between in Persia.
With the growth of urban settlements during the ages, locally dug deep wells (up to 100 meters deep) could no longer keep up with the demand, leading to the systematic digging of a specialized network of canals known as Qanat.
Qanat and Kariz
Persia's Qanat system is thousands of years old.Memarian, Gholamhosein. Asar: Memari-ye ab anbar haye shahr e Qazvin. Vol 35. Iran Cultural Heritage Organization publications. Tehran. p.188 The city Zarch in central Iran has the oldest and longest Qanat (over 3000 years and 71 km long) and other 3000 years old Qanats have been found in northern Iran.p. 4 of The Qanats mostly came in from higher elevations, and were split into a distributing network of smaller underground canals called kariz when reaching the city. Like Qanats, these smaller canals were below ground (~20 steps), and were built such that they were very difficult to contaminate. These underground aqueducts, built thousands of years ago suffer no evaporation loss and are ideally suited for drinking water since there is no pollution danger.
But with the further growth of the city in Persian lands, even the Qanats could not respond to the needs of residents. That is when some wealthy inhabitants started building private reservoirs called ab anbar (Persian آب انبار).
In the middle of the twentieth century, it is estimated that approximately 50,000 qanats were in use in Iran, each commissioned and maintained by local users. Of these only 25,000 remain in use as of 1980.
One of the oldest and largest known qanats is in the Iranian city of Gonabad which after 2700 years still provides drinking and agricultural water to nearly 40,000 people. Its main well is more than 360 meters deep and the qanat is 45 kilometers long. Yazd, Khorasan and Kerman are the known zones for their dependence with an extensive system of qanats.
In traditional Persian architecture, a Kariz (کاریز) is a small Qanat, usually within a network inside an urban setting. Kariz is what distributes the Qanat into its final destinations.
Kariz in Persia Qanats of Gonabad also is called kariz Kai Khosrow is one of the oldest and largest qanats in the world built between 700 BC to 500 BC. It is located at Gonabad, Razavi Khorasan Province, Iran. This property contains 427 water wells with total length of 33113 meters.Qanats of Gonabad-World Heritage This site were first added to the UNESCO's list of tentative World Heritage Sites in 2007, then officially inscribed in 2016 with several other quants under the World Heritage Site name of "The Persian Qanat".The Persian Qanat
According to Callisthenes, the Persians were using Water clock in 328 BCE to ensure a just and exact distribution of water from qanats to their shareholders for agricultural irrigation. The use of water clocks in Iran, especially in Qanats of Gonabad and kariz Zibad, dates back to 500BCE. Later they were also used to determine the exact holy days of pre-Islamic religions, such as the Nowruz, Chelah, or Yaldā – the shortest, longest, and equal-length days and nights of the years.Conference of Qanat in Iran – water clock in Persia 1383 by Dr. M. Ajam, in Persian The Water clock, or Fenjaan, was the most accurate and commonly used timekeeping device for calculating the amount or the time that a farmer must take water from Qanats of Gonabad until it was replaced by more accurate current clocks.water clock in Persia آAmordad Many of the Iranian qanats bear some characteristics which allow us to call them feat of engineering, considering the intricate techniques used in their construction. The eastern and central regions of Iran hold the most qanats due to low precipitation and lack of permanent surface streams, whereas a small number of qanats can be found in the northern and western parts which receive more rainfall and enjoy some permanent rivers. Respectively the provinces Khorasan Razavi, Southern Khorasan, Isfahan and Yazd accommodate the most qanats, but from the viewpoint of water discharge the provinces Isfahan, Khorasan Razavi, Fars and Kerman are ranked first to fourth.
It is Henri Goblot who explores the genesis of qanat for the first time. He argues in his book entitled “Qanats; a Technique for Obtaining Water” the ancient Iranians made use of the water that the miners wished to get rid of it, and founded a basic system named qanat or Kariz to supply the required water to their farm lands. According to Goblot, this innovation took place in the northwest of the present Iran somewhere bordering Turkey and later was introduced to the neighboring Zagros Mountains.
According to an inscription left by Sargon II the king of Assyria, In 714 BC he invaded the city of Uhlu lying in the northwest of Uroomiye lake that lay in the territory of Urartu empire, and then he noticed that the occupied area enjoyed a very rich vegetation even though there was no river running across it. So he managed to discover the reason why the area could stay green, and realized that there were some qanats behind the matter. In fact it was Ursa, the king of the region, who had rescued the people from thirst and turned Uhlu into a prosperous and green land. Goblot believes that the influence of the Medeans and Achaemenids made the technology of qanat spread from Urartu (in the western north of Iran and near the present border between Iran and Turkey) to all over the Iranian plateau. It was an Achaemenid ruling that in case someone succeeded in constructing a qanat and bringing groundwater to the surface in order to cultivate land, or in renovating an abandoned qanat, the tax he was supposed to pay the government would be waived not only for him but also for his successors for up to 5 generations. During this period, the technology of qanat was in its heyday and it even spread to other countries. For example, following Darius's order, Silaks the naval commander of the Persian army and Khenombiz the royal architect managed to construct a qanat in the oasis of Kharagha in Egypt. Beadnell believes that qanat construction dates back to two distinct periods: they were first constructed by the Persians, and later the Romans dug some other qanats during their reign in Egypt from 30 BC to 395 AD. The magnificent temple built in this area during Darius's reign shows that there was a considerable population depending on the water of qanats. Ragerz has estimated this population to be 10,000 people. The most reliable document confirming the existence of qanats at this time was written by Polybius who states that: “the streams are running down from everywhere at the base of Alborz mountain, and people have transferred too much water from a long distance through some subterranean canals by spending much cost and labor”.
During the Seleucid Era, which began after the occupation of Iran by Alexander, it seems that the qanats were abandoned.
In terms of the situation of qanats during this era, some historical records have been found. In a study by Russian orientalist scholars it has been mentioned that: the Persians used the side branches of rivers, mountain springs, wells and qanats to supply water. The subterranean galleries excavated to obtain groundwater were named as qanat. These galleries were linked to the surface through some vertical shafts which were sunk in order to get access to the gallery to repair it if necessary.
According to the historical records, the Parthian kings did not care about the qanats the way the Achaemenid kings and even Sassanid kings did. As an instance, Arsac III, one of the Parthian kings, destroyed some qanats in order to make it difficult for Seleucid Antiochus to advance further while fighting him. The historical records from this time indicate a perfect regulation on both water distribution and farmlands. All the water rights were recorded in a special document which was referred to in case of any transaction. The lists of farmlands – whether private or governmental – were kept at the tax department. During this period there were some official rulings on qanats, streams, construction of dam, operation and maintenance of qanats, etc. The government proceeded to repair or dredge the qanats that were abandoned or destroyed for any reason, and construct the new qanats if necessary. A document written in the Pahlavi language pointed out the important role of qanats in developing the cities at that time. In Iran, the advent of Islam, which coincided with the overthrow of the Sassanid dynasty, brought about a profound change in religious, political, social and cultural structures. But the qanats stayed intact, because the economic infrastructure, including qanats was of great importance to the Arabs. As an instance, M. Lombard reports that the Moslem clerics who lived during Abbasid period, such as Abooyoosef Ya'qoob (death 798 AD) stipulated that whoever can bring water to the idle lands in order to cultivate, his tax would be waived and he would be entitled to the lands cultivated. Therefore, this policy did not differ from that of the Achaemenids in not getting any tax from the people who revived abandoned lands. The Arabs' supportive policy on qanats was so successful that even the holy city of Mecca gained a qanat too. The Persian historian Hamdollah Mostowfi writes: “Zobeyde Khatoon (Haroon al-Rashid's wife) constructed a qanat in Mecca. After the time of Haroon al-Rashid, during the caliph Moghtader's reign this qanat fell into decay, but he rehabilitated it, and the qanat was rehabilitated again after it collapsed during the reign of two other caliphs named Ghaem and Naser. After the era of the caliphs this qanat completely fell into ruin because the desert sand filled it up, but later Amir Choopan repaired the qanat and made it flow again in Mecca.”
There are also other historical texts proving that the Abbasids were concerned about qanats. For example, according to the “Incidents of Abdollah bin Tahir's Time” written by Gardizi, in the year 830 AD a terrible earthquake struck the town of Forghaneh and reduced many homes to rubble. The inhabitants of Neyshaboor used to come to Abdollah bin Tahir in order to request him to intervene, for they fought over their qanats and found the relevant instruction or law on qanat as a solution neither in the prophet's quotations nor in the clerics' writings. So Abdollah bin Tahir managed to bring together all the clergymen from throughout Khorasan and Iraq to compile a book entitled “Alghani” (The Book of Qanat). This book collected all the rulings on qanats which could be of use to whoever wanted to judge a dispute over this issue. Gardizi added that this book was still applicable to his time, and everyone made references to this book.