Page 2: Yazd Region. Coping with the Desert. Innovative Technologies
Suggested prior reading:
|Map of Iran showing Yazd. Base map courtesy Microsoft Encarta|
Living in the desert presents in own set of challenges and perhaps the greatest challenges is to go beyond surviving and coping, to creating a life that is meaningful, productive and enjoyable. And the Yazdis developed some innovative technologies to do just that.
The technologies and systems they devised as conformed to Zoroastrian precepts in that they were environmentally responsible and sustainable. We see this ethic being severely threatened today. The introduction of modern technologies and a dramatic rise in urban population is taxing the environment and can cause irreparable damage. The introduction of deep well drilling and the draining of aquifers at a rate that cannot be sustained is one such example. Indiscriminate urban sprawl and the attendant need for roads and infrastructure is scaring a fragile land and its ecosystems. Modernized industry is making handmade crafts a dying art. It is our hope that the Yazdis themselves can recognize that potential hazards to their historic and sacred land as well as its traditions, and take appropriate steps of preserve their precious heritage.
Kareez (Qanat) - Water Channels
|A kareez channel emerging from its underground (right) to its above ground section (left).|
Note circular shaft opening on the top right hand corner of the drawing. Artist: Salters
A kareez is underground water supply system which has made life in the arid regions of Yazd province possible, especially before the advent of modern technology. This system brings water to settlements and farms from the rain and snow catchment areas in the mountains and hills - from mountain reservoirs, springs and wells. We have an entire page, the Kareez page, devoted to describing the system and its connections to Aryan history.
According to an inventory taken in 2001, there are 3,091 kareez in Yazd province yielding an annual discharge of 339 million cubic metres of water. One of the oldest operating Yazdi kareez is the 900-year-old kareez named yaqoubi that provides the city of Yazd with part of its water needs.
Today Yazd's kareez network measures some 2663.4km in length, with the largest number of kareez in one area - totalling 924.6km in length - being situated in and around the town of Taft. The other major kareez are those that bring water to Aharestan, Dolatabad, Qiasabad and Zarch.
A recent 2008 discovery of a 500 hectare settlement about twelve kilometres from Yazd and nearby a kareez-like system may indicate the use of kareez that predate the establishment the Achaemenian dynasty (675-330 BCE) and we await further the publication of further research on the subject.
In the image to the right, the small waterfall we see caused by a sudden drop in the land, can be used to turn a water wheel - and the water wheel can turn grinding wheels to grind floor.
Watermills - Flour Making Systems
|Horizontal water-wheel in a Taft, Yazd, Iran mill|
The image to the left is that of a water wheel used to grind flour in the village of town just south of Yazd city. When water in a kareez has sufficient flow or force, that energy can be harnessed to do work such as grinding wheat or other grains to flour. This method of using the energy in the water also helps to reduce the flow rate and the damage fast flowing water can do to the kareez tunnel walls. The combination of water wheels and the grinding stones are called watermills. If design properly, the use of watermills in a kareez can have a double benefit - reducing damage to the kareez and making a food. These systems are ancient. They didn't need electricity or the burning of fossil fuels whose smoke would pollute the environment.
Two types of waterwheels are used in a kareez: one that stands upright called a vertical waterwheel, and the other (the one seen in the image to the left) that lies flat called a horizontal waterwheel.
Yak-chawls are ancient icehouses constructed to store ice and keep it frozen through the summer.
Yak-chawls consist of five components:
2. Shade wall around the pool,
3. Ice storage pit,
4. Dome, and
5. An optional badgir
The ice was formed and stored in the following manner: during the winter, a measured amount of water was channelled into the pools where it froze during the night. The shade wall surrounding the pool prevented sunlight from melting the ice. In the morning additional water was added to the pits and in this manner a layered block of ice was built up. After the ice in the pit reached a particular thickness, it was broken into blocks which were transferred to an deep underground ice storage pit covered by a dome which is sometimes conical in shape. The temperature in the ice storage remained low enough to preserve a fair quantity of ice through the winter and until the next winter.
If the yak-chawl has access to a kareez (see section above and our Kareez page), the underground water distribution system, a badgir cooling system used in conjunction with a kareez can help to cool the interior of the yak-chawl and hereby help to keep the melting of the stored ice to a minimum (see image to the right). We should note that the yak-chawl in the image to the right also looks like an ab-anbar, a water storage tank kept cool by badgirs. The principle difference between the two is that the former stores ice and the latter stores water. Both can be kept cool by badgirs.
All these systems: the kareez, badgir and yak-chawl are environmentally friendly. They do not use an bio-fuels. They are also sustainable and follow Zoroastrian precepts of not harming the environment when used correctly according to the traditional methods.
|Inside the ice house - the ice pit|
|Ab Anbar constructed with a donation by Arbab Rostam Guiv|
Ab anbar (آب انبار) means 'water storage' in Persian. Ab anbars were the terminal point for many kareez, the underground water channels that bring water, in this case, for urban consumption. The water stored in these storage facilities is then individually collected for personal use. The wealthy or otherwise fortunate had and have private storage facilities - as well as cooling systems attached to the kareez.
The common person had to come and collect water from the ab anbar. For this reason, it was essential for ab anbars to be located in each neighbourhood within walking distance of the eventual user. The individual user did this by descending steps into an ab anbar, and filling a water container with water which they had to carry back home. Alternatively, water carriers made a living by delivering water from an ab anbar in a goat skin bag strung over their shoulders. The water carrier would go from door to door offering to sell water to a householder.
The image to the right is that of 'Ab-Anbar-e Rostam Guiv (also spelt Giv)' a well-known landmark in Yazd city and an example of Zoroastrian community service. Arbab Rostam Guiv was a well-known benefactor of the community and we have a section describing his work in our page on Zoroastrians & Zoroastrianism in the Yazd.
Offsite image page: IranPix
Ab Anbar Technology
The technology that goes into the construction of these ancient structures is not so evident at first glance but quite amazing once we start an examination.
At the outset, the ab anbar needed to be strong enough to withstand the huge pressure exerted by the water stored. A related need was the ability of an ab anbar to be earthquake resistant since the region is beset by violent earthquakes. Both needs were met by constructing the storage below ground, a required feature since the water flowed by gravity from the water tunnels of the kareez into the anbar.
The thick brick walls were also superb insulators, preventing warming and freezing of the stored water.
The ab anbar structure was constructed using special materials. The walls of the storage, commonly two metres thick, were built using specially baked bricks called ajor ab anbari. A special mortar called sarooj was used the bind the bricks, and it was made up of specific proportions of sand, clay, egg whites, lime, goat hair, and ash. The mortar component proportions were custom formulated for different areas and climates. The resulting wall was water-proof and earthquake resistant as well. Large ab anbars that served single large users such as caravanserais or places of worship were built directly under the edifice.
Depending on the location, ab anbar construction technology was incorporated with the badgir (wind catcher) cooling technology. Where needed, one to six badgir towers provided ventilating and cooling to prevent air stagnation and humidity accumulation air thereby preserving the integrity of the water and a year round supply of pure, clean, cool water.
The Yazdis have developed some innovative ways of keeping cool, methods that are not sure environmentally responsible, but also those that created or were part of an aesthetically pleasing environment - all in consonance with Zoroastrian precepts to respecting and not polluting in elements of nature.
Badgirs - Wind-Catchers
|Schematic diagram of the badgir cooling system with added cooling aided by a kareez/qanat|
|Badgirs define city of Yazd's skyline|
|Hexagonal badgir (tallest in Yazd at 33 m) at the Dowlatabad Palace gardens|
Badgirs or wind-catchers are towers with openings at the top that help in cooling a building through natural and environmentally friendly methods that capture the wind that blows over the buildings. The skyline of city of Yazd is defined by badgirs rising from the city's buildings. One of the most prominent badgirs in Yazd city is the thirty-three metre high badgir of the former palace of the Karim Khan Zand (c. 1705- 1779 CE). The palace, built in about 1750 CE, and its grounds are now a public park called the Dowlatabad Gardens (see photograph to the right).
[Karim Khan Zand was a general in the army of Nader Shah Afshar (1688 - 1747 CE, a murderous monarch who butchered many Zoroastrians and prohibited their travel outside the country. It was not uncommon for many Zoroastrian women to be abducted by Muslim men and turned into 'wives' or sex slaves during Nader Shah's reign.) For a brief period between two incompetent monarchies, Karim Khan became the uncrowned ruler of Iran.]
The badgir essentially creates a draft which prevents hot air from accumulating. The badgir tower rises high enough for it to catch the breeze that blows across the top of buildings, trap the breeze, and then direct the trapped breeze down through a chimney into a building. The way in which the draft through a building is created is by the section facing the breeze catching and compressing the air and directing it down through the building, into the building's lowest level, say a basement if the building has one. Since the breeze flowing over the top of a building can come from various directions and can even change direction frequently, many badgirs were created with four or more faces on each side of a square (or polygonal - see the photo to the right) chimney-like tower. In other words, badgirs come with one, two, four and even five faces (like the badgir in the photo to the right).
|The view up a two-section badgir chimney shaft. Image credit: Azad Yasamin at Flickr.|
|The view up a four-section badgir chimney shaft. Image credit: Yasinpix.|
The up and down chimney shaft itself is divided into the same number of sections as the badgir face. For instance, if the top opening of the badgir has four faces or openings, the chimney shaft itself must also be divided into four sections. Dividing a square chimney into four gives us four triangle shaped shafts that run up and down the chimney.
However, if the badgir merely traps a current of wind, the draft created within the building will be mild. To increase the draft flow rate, the openings of the badgir that are opposite to side facing the wind, create a suction effect that suck out the air from a building.
If there is no wind, the south face of the badgir tower heats up and since hot air rises, the air in the southern section will rise up sucking the air down from the cooler section that faces north.
At night, The tower cools down first and the cold air being heavier than warm settles down through the chimney into the building, pushing out the warm air through the windows, creating a draft and cooling down the building at the same time. As the mud bricks don't conduct heat readily, while they may take time to cool down at night, they will also take time to heat up during the day. If there is a large pool of water in the house, that too will cool down and become a heat sink absorbing heat during the day.
|Basement room with a small pool to cool the|
breeze coming in from a badgir.
Note benches on the four sides of the room.
Image credit: Azad Yasamin at Flickr.
Stage two creates the wind action that a fan working in conjunction with an exhaust fan would create. To enhance the cooling, in those buildings with owners that had the position and wealth to afford such a system, the badgir and water storage systems were combined to create the effect of a water cooler. This is accomplished by passing the draft created by the badgir over a pool of water - say a small pool or reservoir in the basement. If a home was fortunate enough to afford this system and construction, the basement room was converted into a gathering room with ledges that served as seats and beds for an afternoon nap.
Stage four is to make the badgir works in conjunction with an underground water channel, kariz. The temperature of the flowing water in a kareez was generally lower than in a standing pond and a long kareez channel provided a larger cooling surface area as well. This system created a temperature drop as much as 200C.
In this stage the microclimate created by a badgir is enhanced by a courtyard that includes a pond and garden. If the section of the badgir facing the direction from which the breeze is coming is blocked, and if instead the incoming air is taken in from a shaded courtyard with a pool and a garden, the incoming air will be somewhat cooler, and the courtyard itself will benefit from the induced draft. This system was and is exploited by the town's wealthiest residents.
The layout of the traditional houses of Yazd helps in creating a cool microclimate in summer and warmth in winter. This layout included the construction of a house's rooms bordering a square or rectangular courtyard. The windows of the rooms face the courtyard rather than the street and in the centre of the courtyard was a pond surrounded by plants (fragrant flowers and fruit trees) as shown in the images below.
A takht (raised platform) placed over the pond provided in the early morning or late evening during the summer, a cool seating place for a number of people. By surrounding the courtyard with rooms of the house enabled the courtyard to be shaded during the early and late daytime hours. The wind from the badgirs or wind-catchers would be channelled into the courtyard creating a cool breeze and the rooms that opened onto the courtyard also benefited from the cool breeze.
|Takht over a pond at Khuneh Lari (Lari House), a large traditional Yazdi house.|
Image credit: Wikipedia