SH Archive Qanat Tunnels, UNESCO World Heritage Sites

[Archive]

I'd never heard of these before, reading the wiki page I do believe they belong in this forum. O yeah, they are UNESCO sites too. A qanat or kariz is a gently sloping underground channel to transport water from an aquifer or water well to surface for irrigation and drinking, acting as an underground aqueduct. This is an old system of water supply from a deep well with a series of vertical access shafts. The qanats still create a reliable supply of water for human settlements and irrigation in hot, arid, and semi-arid climates, but the value of this system is directly related to the quality, volume, and regularity of the water flow. Traditionally qanats are built by a group of skilled laborers, muqannīs, with hand labor. The profession historically paid well and was typically handed down from father to son. According to most sources, the qanat technology was developed in ancient Iran by the Persian people sometime in the early 1st millennium BC, and spread from there slowly westward and eastward. However, some other sources suggest a Southeast Arabian origin.

• Qanat - Wikipedia

A qanat tunnel near Isfahan


Cross-section of a Qanat
​

Sorry for the short write up, and i hope they interest some of you.
Thanks

Note: This OP was recovered from the Sh.org archive.

Note: Archived Sh.org replies to this OP are included in this thread.

 

[KD Archive]

Note: This post was recovered from the Sh.org archive.
Username: KorbenDallas
Date: 2020-01-04 00:25:52
Reaction Score: 0

Wondering how they measured this barely noticeable slope while burrowing. Hmm.

 

[Archive]

Note: This post was recovered from the Sh.org archive.
Username: OpenMind
Date: 2020-01-04 01:23:33
Reaction Score: 0

Wondering how they measured this barely noticeable slope while burrowing. Hmm.

It's the depth that made me sit up and look, as well as the very slight gradient. As they started digging the opposite end to the water flow.

 

[feralimal]

Note: This post was recovered from the Sh.org archive.
Username: Feralimal
Date: 2020-01-04 09:22:17
Reaction Score: 1

The thing that struck me, is why the need for shafts at all? If they worked backwards into the water table they could get the slope they needed.

The page says the shafts are essential, and a distinguishing feature. I don't doubt it. I just wish they would say why!

The qanat should not be confused with the spring-flow tunnel typical to the mountainous area around Jerusalem. Although both are excavated tunnels designed to extract water by gravity flow, there are crucial differences. Firstly, the origin of the qanat was a well that was turned into an artificial spring. In contrast, the origin of the spring-flow tunnel was the development of a natural spring to renew or increase flow following a recession of the water table. Secondly, the shafts essential for the construction of qanats are not essential to spring-flow tunnels.

The nearest they come to an answer is this:

The vertical shafts support construction and maintenance of the underground channel as well as air interchange. Deep shafts require intermediate platforms to simplify the process of removing soil.

While you might dig one shaft to confirm there is water where you expect (like a well), the rest of the shafts sound like extra work!

Anyway, what do I know! There probably is a good reason, but I don't get it from wiki. No change there then!