Finding Water When Rain Does Not Fall

The Middle East may have had a very different climate in 700 BCE, but it did have one thing in common with the climate today, rain was definitely seasonal. One thing we know, is that despite the seasonal rains, people managed to do more than just scrape out an existence, they thrived. So how did people living in areas such as modern day Iran manage to find water in an area that is known for being in some places hyper arid?

Qanat Irrigation

A qanat, as they were called by the Persians, is a series of vertical tunnels that were hand-dug by a single person, to a single horizontal shaft. The horizontal shaft would start at the outer reach of an alluvial fan running off of a mountain, and run to the base of the fan itself where the water table was at a higher elevation than the beginning of the shaft, usually tapping in to an aquifer. The vertical shafts, which were covered after use, would be used during the building process for ventilation and removal of material from the construction of the horizontal shaft, and would be later used as access points for maintenance. [Wulff] The beauty of qanat style irrigation is in its simplicity. The water that flows from the base of the alluvial fan is fed by gravity to the opening of the horizontal shaft at a constant flow, which eliminated the need to pump the water at any stage. Since the vertical shafts were dug instead of a large trench, the flow of the groundwater down the main shaft is covered and therefore not subject to evaporation by the sun. Qanats were also notoriously very reliable, since the ground water was not pumped out, it was allowed to flow at its own pace, therefore not drying up aquifers from over use.

Building a Qanat

Dating when qanats were first constructed is very difficult, however the written records show that the birthplace is more than likely in modern day Iran. The earliest reports of qanat irrigation is from the 7th century BCE, from the Assyrian King Sargon II, who reported finding a way to tap in to ground water during a Persian campaign. King Sargon’s son, King Sennacherib later used this idea to build the underground irrigation system around Nineveh. Qanats are also found in most of the countries conquered by the Persians from 550-331 BCE, from the Indus Valley to the Nile, and expanded upon more by the Romans, reaching as far as Luxembourg. [Moki Systems]

Although qanats were developed almost three thousand years ago, they are still very popular around the world today. In Iran alone, seventy five percent of the water used in the country, for irrigation and household use, is supplied by qanats. There are around 22,000 qanats, with more than 170,000 miles of underground channels. [Wulff]

Iranian Qanat

Bibliography

H. E. Wulff. “The Qanats of Iran.” Scientific American. April 1968, p. 94-105 http://users.bart.nl/~leenders/txt/qanats.html

Moki Systems. “Qanats.” Waterhistory.org Provo, UT

http://www.waterhistory.org/histories/qanats/

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