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Iran: 2000-year-old technology stands the test of time

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Two wind towers flank a water reservoir in a small desert village in central Iran. Photo / Jill Worrall
Two wind towers flank a water reservoir in a small desert village in central Iran. Photo / Jill Worrall

Light spills into the garden pavilion of Karim Khan Zand like a shower of jewels-bright reds, yellows, blues and greens.

Arched windows of stained glass have taken the unrelenting Central Iranian sun, softened and coloured it, creating kaleidoscopes of light across the pavilion floors, making this truly a haven for royalty.

Karim Khan Zand ruled the desert city of Yazd during the 18th century and he had his garden and house build in about 1750. Apart from its exquisite windows it has another unique feature: it was built by the great, great, great, great-grandfather of the man who is standing beside me.

Reza, who thinks there may be a great or two missing from his recollection of his family tree, is however, certain that his ancestor designed the wind tower that rises above us. It is the tallest in Yazd and at 33 metres is also believed to be the tallest remaining in the whole of Iran.

I've travelled with Reza many times before but this is the first time he's told me about the family connection. I ask him why he's not done so before.

"It seemed like boasting somehow," he replies.

We discuss the difference between boasting and being proud of one's ancestors. Despite this, it's me, not him, who tells the Kiwis we're travelling with about the link.

Wind towers, or badgirs, are a Persian invention, probably dating back about 1000 years.

Arabs living across the Persian Gulf may disagree but the Iranians are adamant that any such structures found in places such as Dubai are of Persian origin.

Wind towers are natural methods of air-conditioning that rely on convection currents and the cooling effect of water.

The towers, which can have up to six sides, are oriented towards the predominant wind flow and are fitted at the top with louvres that direct the air.

The central shaft is divided into compartments that, depending on which way the wind is blowing, either draw in or expel cool or warm air.

Fresh air sucked down one set of compartments flows over a fountain and small pool beneath, which further cools it. Warm air is drawn up the other shafts.

Reza directs me to stand under one of the shafts, takes a tissue from his pocket and throws it into the air. It immediately catches a draft and is whipped high up into the 35-metre-tall badgir and then away. We move around to stand beneath another shaft - the dip in temperature is immediately obvious.

"I think it's a shame that more new houses are not being built with badgirs," Reza explains.

"They use no energy, they are not noisy and the cooled air is more natural."

The badgirs are also used to cool water held in traditional reservoirs, some of which are still in use in the old quarters of Yazd.

These reservoirs are part of another fascinating example of Persian technology - the qanat.

Qanats were first used on the Iranian plateau at least 2000 years ago and many are still operational today. It's hard to imagine too many pieces of current technology proving just as effective in the year 4009. The technology spread, partly in tandem with the spread of Islam, as far as China, North Africa and even to the New World (via Spain).

Qanats are underground irrigation channels and there are more than 50,000 in Iran. Although some have fallen into disuse many are still essential parts of farming and daily life in some of the driest parts of the country.

A recent drought, which rendered many conventional wells and irrigation systems useless, prompted farmers to restore their qanats and they functioned extremely well.

Water enters a qanat from deep wells or from run-off high in the mountains. It flows into a tunnel just wide and high enough for a man to walk through that has been dug with a gentle downhill gradient. As long as the bottom of the well at the start of the qanat is at a higher elevation than the qanat end point, the water flows with no other assistance.

The tunnels can be up to 40km long. Every 20 metres or so, they are intersected by a downward shaft which provides ventilation and also access for the specialised qanat builders.

The water flows into towns for drinking water (often the central reservoir is under a mosque), would have once also provided water for traditional bath houses before flowing out into gardens, orchards and farmland.

Because it flows through natural gravels and under ventilation shafts and badgirs the water from qanats is often remarkably clear and cool.

Being so deep underground there is also little evaporation and irrigation experts believe that because the flow rate is controlled by the level of the underground water table, a qanat cannot cause significant drawdown in an aquifer.

From above ground the qanat system looks rather as if a giant mole has been at work. The entrances to the vertical shafts are mounded up like small volcanic cones (which stop surface run-off from contaminating the water). The shaft itself is blocked with thornbushes or a slab of rock to prevent rubble, people or animals from falling in.

The job of maintaining this extensive system is handed down from father to son. It's skilled work, uncomfortable and can be dangerous. There's little room to manoeuvre along the tunnels and often no protection if the roof caves in. Only tunnels in very loose soils were reinforced with rings of burnt clay.

"What is especially remarkable is how tunnellers, working from different ends of the system knew how to align their tunnels," Reza explains one day, while moving a rock out of the way so we can see and hear the water rushing past below.

"They would take a drummer down at each end - and the sound would guide them."

Another equally ingenious system was used to determine that everyone who had access to the qanat took only their share of the water.

A respected local elder would be assigned the job of timing the release of water into individual properties. He would do this by scooping up a small brass bowl of water from a larger bowl and letting the water pour through a small hole at its base. This way a pistachio grower who had an allocation of the equivalent of, say, 20 bowls' worth of flow, could be sure he was not being cheated.

Qanats, and their regional variations, are being promoted by Unesco as a viable and sustainable irrigation system in many countries.

Maybe wind towers should be added as another form of alternative technology - I know that on a hot summer's day I'd rather be reclining in a pavilion, showered with coloured light while a fountain plays and a cool breeze wafts by than listening to the dry hum of an air-conditioner.

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