Qanat: Iran’s Ancient Water Management System

A qanat is an underground channel that carries groundwater to the surface by gravity. Also known as a kariz, it connects a water source on higher ground with fields and settlements below. The visible line of shafts marks a much larger structure hidden beneath the landscape.

Understanding a qanat means looking beyond its tunnel. Excavation, maintenance and agreements over water all contribute to the system. This guide explains the engineering; our companion article explores the culture and communities of qanats.

How a Qanat Works

The upstream section reaches a water-bearing layer. Water seeps into the channel and travels along a gentle gradient until it emerges at the outlet. From there, surface channels distribute it to the land it serves.

A mother well helps establish the depth of the water source. Other vertical shafts connect the tunnel to the surface, providing access for excavation and repairs. Their openings and the surrounding excavated earth create the characteristic rows visible from above.

The slope needs careful calculation. It must allow water to flow without causing excessive erosion. Length, depth and shaft spacing depend on the terrain and water source, so measurements from one qanat should not be treated as a standard for all of them.

Building and Maintaining the Tunnels

Specialist workers, known as moqannis, survey, excavate and maintain qanats. Work can include removing sediment, repairing collapsed sections and reinforcing unstable ground. The skills needed are described in Encyclopaedia Iranica’s account of qanat technology.

The underground route reduces the water’s exposure to sun and wind during transport. Gravity moves the water without a pump, but maintaining the tunnel still requires labour and technical knowledge.

Why Flow Can Change

A qanat does not create water. Its output depends on the groundwater available to it. Seasonal recharge, drought, competing withdrawals and the condition of the channel can all affect its flow.

For this reason, gravity-fed transport is not a guarantee of unlimited supply. A falling water table can reduce or stop the discharge. Iranica’s discussion of water supply distinguishes continuous flow from constant flow and describes how local conditions influence it.

Conservation also involves the people who maintain and use the system. Changes in land ownership, water demand and the availability of skilled workers can affect its future, as discussed in Iranica’s review of modern qanat challenges.

The Persian Qanat World Heritage Property

In 2016, UNESCO inscribed The Persian Qanat, a serial World Heritage property comprising eleven qanats. The designation recognises both their engineering and the traditions of managing shared water resources. It does not mean that every qanat in Iran is individually World Heritage listed.

The official UNESCO listing describes associated reservoirs, watermills and other structures. For examples, read about Qasabeh Qanat in Gonabad and Zarch Qanat in Yazd.

Understanding Qanats on a Visit

Start with the relationship between the shafts, the outlet and the surrounding fields. An interpretation display or cross-section can explain features that are difficult to see from ground level.

Ask your guide which parts are accessible and whether the water is currently flowing. Follow site instructions and use designated visitor routes. A qanat is a working water structure, and access arrangements differ between sites.

Further Reading

Wulff, H. E. (1966). The Traditional Crafts of Persia: Their Development, Technology and Influence on Eastern and Western Civilizations.

Nadji, M., and Voigt, R. (1972). “Exploration for Hidden Water” by Mohammad Karaji: The Oldest Textbook on Hydrology? Groundwater, 10(5), 43–46.