(Dis)proving the historical narrative of a massive agricultural system in Southern Iraq

Date of news: 16 December 2021

Landscape archaeologist Dr Peter Brown has received a grant from the Gerda Henkel Foundation for a collaboration with researchers in Iraq and the United Kingdom. Together, they aim to date the remains of a medieval agricultural system near the city of Basra in Southern Iraq.


In the early to mid-7th century the city of Basra was founded in Southern Iraq. Today, the city is situated on the Shatt al-Arab river, but the city was originally founded about 15 km inland as a garrison encampment for Arab tribesmen. The city had problems with its water supply but historical descriptions of the surroundings describe agricultural fields and date plantations irrigated by canals which brought water from the river. The city rapidly grew into one of the largest cities, not only in Iraq, but across the entire Islamic world.


Remains of a massive irrigation system covering over 50,000 hectares surround the site of the medieval city. At some point, this system was abandoned. The city of Basra seems to have gradually declined from the 10th century and was eventually entirely relocated to its present location on the banks of the Shatt al-Arab.

‘Not much survived of the original medieval city, so what we know about it is limited'

The remains of the agricultural system today consist of a regular pattern of ridges of soil in straight lines, separated by old canal beds. The ridges are about a kilometre long and up to four or five meters high. Although there has been much speculation and theorising about the water management system, the exact origin and date of these features are not scientifically known. ‘Not much survived of the original medieval city, so what we know about it is limited’, says landscape archaeologist Dr Peter Brown. The Gerda Henkel Foundation has now awarded him a grant to investigate the irrigation system near Basra. ‘The question is, what are these ridges exactly and are they related to the medieval city? We need to understand that to place them in a wider historical context.’

Historical sources

There are various theories about how and why the ridges in the agricultural system came into being. An important clue might be their high salinity. Water on the irrigated land may have evaporated, leaving behind layers of salt. Brown: ‘At the time, Basra was a big slave market. The enslaved people are known in historical texts as the Zanj and are often assumed to have been brought to Basra form East-Africa—though they may have had more diverse origins. Historians have suggested that the enslaved Zanj people were put to work in the surrounding landscape of Basra. One theory is that they were forced to dig out the salty topsoil and pile it up into ridges so that the land in between could be used again.’

'It is important to see how the salt content changes throughout the layers of the ridge'

However, another theory is that the ridges themselves were an agricultural strategy and farming took place on the raised areas on top of them. In that case, the salt layer on the ridges could have developed through natural processes. ‘If they were constructed during the medieval period, they have been there for about a thousand years. That is plenty of time for them to have naturally built up a high salt content’, Brown explains. ‘But these are just theories at this point. It is important to see how the salt content changes throughout the layers of the ridge. If they are salty at the top, but not further down, it suggests that the salt has built up naturally. Whereas if they are consistently salty throughout the different layers of the ridge, that would make a stronger suggestion that it was salty soil to begin with.’

Radiocarbon dating and satellite imagery

The grant allows Brown to work together with his Iraqi colleague, Dr Jaafar Jotheri of the University of Al-Qadisiyah in Iraq, and Dr Louise Rayne of the Newcastle University (UK) to try and date the ridges. The grant runs for two years, starting now, and the project consist of two parts. In the first part, Dr Jotheri will co-ordinate small excavations into the ridges and the canals in between to take samples that can be scientifically dated with radiocarbon dating (C14) and optically stimulated luminescence dating.

With Dr Rayne and Dr Jotheri, Brown will also gather commercial satellite imagery of the irrigation system to create a detailed 3D model of the ridges and canals. Brown: ‘That will allow us to do further analyses to see how water flows through it and to get a better understanding of how the system might have worked in the past.’

Historical narrative

The dating-process could also reveal that the ridges are much more modern, Brown says. ‘They might be only 200 years old for instance. But that would be equally interesting and important to know. It would disprove the accepted historical narrative.’ However, if the team can date the ridges as medieval features - consistent with medieval documents - it would demonstrate a strong link between the enslavement of the Zanj, the medieval city and the agricultural features. Brown: ‘The Zanj people are a very important part of Islamic history. They rebelled in the late 9th century and the Zanj Rebellion is a key event in Islamic history. Although this project will not be able to prove a definite connection between the Zanj and the irrigation system, if the ridges and the canals are from the same period as the presence of the enslaved Zanj people, it would provide a strong link.’

Source of Life project
Peter Brown is a postdoc in the vici project Source of Life. The project examines exactly how the urban communities of Baghdad, Basra, Mosul, Samarra, Damascus and Cairo were able to successfully manage water over the long-term. Within these six cities, this includes mapping the various formal and informal arrangements that exercised control over water as well as the driving forces for change and evolution within these water management systems.