While attending the Rural Water Supply Network (RWSN) forum in Kampala, Uganda, last week, I talked to Lucie Dupertuis. She works in Iraq, and I wrote down her story below.
Top: Lucie Dupertuis.
“I work in Iraq, with an organisation called International Organisation for Migration (IOM). I got interested in water supply and specifically in the traditional system of karez (known as qanat in Iran), which are underground galleries which drain the water of the aquifer, and transport it to a place where it can be used.
“The system of karez is used in some 34 countries around the world, and the oldest systems in Iran are about 2500 years old. Up to the 1970’s, the karez’s delivered about 75% of the Irani water supply. After that, pumped wells and dams started to play a bigger role.
“One of the good things about the karez is that it has sustainability built in. As it drains the aquifer instead of actively pumping it, it can never over-exploit the groundwater. This is really important because groundwater depletion is a huge problem. Only 40 years ago, the groundwater table in Yazd, a city in the central part of Iran was 40m deep, while now it is 100m deep. In the city of Erbil, the level went from 20m to 80m in 30 years. Actually, under Sadam Hussein the water extraction was quite well regulated, but when he was removed, the extraction increased very much.
Cross section of a Karez. Source: Wikipedia.
“Let me explain how a karez is made. You start by identifying a site where you would like to use the water, for example for irrigation. Then, some distance up hill, you make a hand-dug test well to see if there is water there. If you encounter water, this becomes the ‘mother well’. From the exit point, you now start digging towards the mother well, almost horizontally. The Karez should have a very small slope, only 0.01-0.02% If it is too steep, it will erode, if it is not steep enough, it will stagnate. The part in the aquifer is called the wet part of the karez, the part above the aquifer is the dry part — this just drains the water collected in the wet part.
“While moving towards the mother well, you dig more vertical wells at regular spaces, to provide access and ventilation, and remove sand and rocks. If the soil is loose, the tunnel is reinforced, for example with rings of baked clay. A smart system with candles is used to check if oxygen is still present, and if the digging proceeds in a straight line. Candles are placed at regular distances, and the digger only needs to look back and check if all the candles are still aligned with each other to know if he is going straight.
“The length of a karez can vary by anything between tens of kilometers and tens of meters. The longest one known, which is in Iran, is 75 km long, while most karez’s in Iraq are only tens of meters long, because they are situated in mountainous areas. Ventilation is also very important. In Azerbaijan, where we also worked, we used a modified vacuum cleaner to provide fresh air while digging. Digging a karez is dangerous work. You can drown when underground dams break through, there can be poisonous gases, and walls can collapse.
The exit of a karez in Niavaran, Tehran. It is used for irrigating the grounds of the The National Library of Iran. Source Wikipedia.
“Most of the knowledge on how to build and maintain a karez is concentrated in Iran. There is a special centre, the International Center for Qanat & Hydraulic Structures (ICQHS). Unesco plays a role in training engineers in Iran in this field. In Iraq, the knowledge is very rare. Karez’s in Iraq are usually made by Iranian experts. I met one karez expert in Iraq, who was the son of an Iranian Kurd, and he had learned the trade from his father. He trained the people in his family, and they now form a knowledgeable karez digging and maintenance company.
“In Iraq, it is quite rare to build new karez’s, but existing ones need to be maintained. The problem is that the government contracts this work out to construction companies who often don’t have the knowledge to do this properly. One of the common mistakes is to line the karez with concrete, but this seals it off from the aquifer and ruins the karez.
“What I would like to see is that the companies get better skills in maintaining this historic and sustainable resource. I am thinking about ways to get that done.”
Mark Tiele Westra is Akvopedia editor and programme manager at Akvo