One of the most important elements of living is water which has always been a crucial and sometimes controversial issue, specially in arid lands like Iran. Because of the climate, Iranians have made an innovative method to satisfy their needs of this vital element. In fact this invention led to transfer underground water as far and use it during the whole year, like a spring. This innovative method is called “Qanat” or “Kariz” that is registered in the UNESCO’s world heritage list.
Qanat is an underground canal to transfer water. It’s said that the oldest Qanats date back to the 3rd millennium B.C, it is located to the west of Iran in Elam province. In addition, during the 7th century B.C Sargon the 2nd, an Assyrian emperor, mentioned that he had found some Qanats during his campaign to the northwest of Iran. In 2003, after the earthquake in Bam, in Kerman province, a 2000-year Qanat was discovered which refers to Achamanid dynasty. In fact that time was the flourishing time of this admirable technique, in all around the empire many of them were constructed, however the number of Qanats in Iran is more than the others in the world. Actually, this method helped them to cultivate and farm in the arid lands. Even, according to historians, Achamanids conquered some cities by digging underground canals.
Although the construction of this innovative method is simple, it is needed to do by experts. The first step is detecting where to dig which is located on the domains of mountains. To ensure, some well will be dug to confirm that this is the place of the master or the main well. Digging has to be done during autumn in order to be as deep as possible. Then, the slope of Qanat calculates with a plummet, usually it is 1/1500. The water spoils if it does less and if it calculates more the structure will be erode and collapsed. Also, the height of the wells calculates and checks with plummet. But, it is not as easy as it seems, because the difference in the height of the ground must be taken into account. Digging should be begun from the outlet, the last well, if water flew in the canal it can exit easily. The next step is determining the direction. First the direction determines with a thread. Within one meter, two marks are made on the string and a well is dug beneath them. Then after digging two lights are put in the well, toward the direction and exactly under marks. During the excavation, diggers should look at lights in order to not to miss the direction, it is true when they see just a light. In addition, many vertical shafts, false wells, should be dug in the distance of the master well and the exit, usually within 20 or 30 meters, to ventilate, remove grits or access for repairs, as if they are series of holes. Also, the length is depend on the slope of the ground and how much it is far from the source.
Usually these master pieces of irrigating and water supplying system are done in deserted areas, where the amount of precipitation is less than 300 mm yearly. They may also flow beneath cities in tunnels and can be used in cisterns or ponds. Moreover, they could help cooling buildings as well as supplying water, specially where they are located beneath the wind catchers. In fact, wind towers attract and circulate wind through its structure and the well beneath it Which finally cools the building, a passive cooling system. Beside, in some Qanats there are dams, like “Vazvan”, that are closed since autumn till spring that helps preserving water. This exceptional Qanat was built during Sassanid dynasty. The longest one is “Zarach” in Yazd. This pre-Islamic Qanat contains 2115 wells and Yazd Jame mosque is irrigated by it. “Qasbeh Gonabad” is the deepest Qanat in Iran, its master well is about 300 m deep.
Qanat is a hand-dug tunnel to supply and transfer water for dry lands. In fact, Qanat is an Arabic word, in Persian it is also called “Kariz”. This method has helped Iranian farmers to provide water despite lack of surface water. Actually it is a technical procedure to identify an underground reservoir and transfer it to a region that should be done by experts. This appreciated technique is rooted in Ancient Iran, bronze or iron age, and during Achamanid dynasty was spread in the empire.