Zarach Qanat (Zarach Aqueduct), the longest Qanat in the world is located in Zarach City, Yazd province, Iran. This aqueduct emanates from Fahraj village, 60 km away from Yazd. It is one of the most ancient Qanats in Iran, about 3000 years old, and is estimated to belong to Sassanid dynasty.
The Qanat length is 80 km (with branches) at a depth of 23 meters. There are also 2115 vertical access shafts on the route of the Qanat. This Qanat is known as the longest Qanat in the world and one of its features is its square section.
Creating a reliable supply of water for the major human settlement in Yazd and providing irrigation in hot and arid villages of the suburban areas, the Qanat transported water as long as 120 kilometers and watered 425 hectares of land.
The Qanat also powered the Vazeer Mill in Koushk No district of Yazd city where it passes 30 meters below the surface of the city and has a slow sloping entry into the mill.
Plans are devised for restoring and conserving the section of Qanat between the Vazeer Mill and the Jameh Mosque of Yazd (also known as the grand congregational mosque of Yazd city) where there are 7 payabs and 2 pasheers on the passage.
Pasheer is an underground chamber for dispensing water where one or sometimes more bronze faucets are provided to get water from the water reservoir (Ab anbar) behind the wall.
Payab is a stairway leading to an underground chamber where there is a polygon slice on the floor on the passage of Qanat to provide access to water.
An indigenous Iranian structure, a Qanat is a gently sloping underground channel with a series of vertical access shafts, used to transport water from an aquifer under a hill. Having been developed by the Persian people, the technology is seen in the fourth millennium BC in Iran and spread from there slowly westward and eastward.
A part of the Zarach Qanat can actually be accessed within the Great Friday Mosque. Inside, there is a small opening on the ground that can easily be missed which leads to a payab (underground water chamber). This payab, which has been supplying the mosque the water it needs since it was erected, is one of the public openings of the Zarach Qanat. The properly lit stairway goes down to some 30 meters below the ground until one reaches the well. Going down through its small opening, several layers of water channels and chambers can be seen. Apparently, the site lies at the crossroad of three different Qanats, with the Zarach Qanat specifically powering the mill. It is also interesting to know that the temperature on the ground compared to the temperature down where the waters flow can differ from 17 to 20 degrees Celsius, making it a wonderful refuge from the heat outside.
The Zarach Qanat runs as well under the Amir Chaqmaq Complex, but going there proved futile – there is no way to “see” the Qanat.