New discovery: Great Zimbabwe had an extensive water management system
Great Zimbabwe, the largest city in southern Africa during the Middle Ages, made use of dozens of large pits to store water. A new study reveals how this system allowed the community to manage a stable water supply in a region prone to drought.
LOCATED in the mountains of southeastern Zimbabwe, Great Zimbabwe was founded in the 9th century.
The name Zimbabwe itself means “the big stone house” in the Shona language, and in fact the country got its name from the ancient city. By the 11th century it was the capital of the Shona kingdom, overseeing parts of present-day Zimbabwe and Mozambique. With a population of between 10 000 to 18 000, the city flourished until it was abandoned in the 17th century.
But how did the people living there fulfill their needs? Particularly challenging was water – Great Zimbabwe is located in a climate-sensitive area so ensuring a stable supply of water for so many people and so many cattle must have been a problem.
This mystery has been investigated by a group of researchers from South Africa, England, Zimbabwe and Denmark in an article published in the journal Anthropocene. With remote sensing methods and excavation, they investigated a number of large depressions in the landscape, which are locally called “dhaka” pits. The depressions have not been investigated before, as it has been thought that they were made only to collect clay used for building in the city.
The new investigations show that the pits must also have been used to store and manage water for the city. There are clear signs that the depressions have been excavated where they can collect surface water, and at the same time seep and store groundwater for use during the dry periods of the year.
The researchers found more “dhaka” pits than were known before, and they have been found where small streams will naturally run through the landscape when it rains or where groundwater seeps out. This, combined with the location and construction of the depressions, has convinced the researchers that the “dhaka” pits functioned as a clever system to ensure a stable water supply, by storing more surface and groundwater that could be used outside the rainy season as well. They estimate the system could have stored 18 000 cubic metres of water.
The people of Great Zimbabwe thus devised climate-smart methods for storing and managing water in an area that is characterised by having three different climates, with a very warm and dry season, a warm and wet season and finally a warm and dry winter. Such a water supply may have been essential in order to create an urban society that required a safe supply of water for its inhabitants, for livestock and for agriculture.
The researchers write: Though fragmented, the growing body of environmental and archaeological records when integrated with historical and ethnographic information, do paint a new, convincing portrait of Great Zimbabwe: a landscape where human settlement, land and water were intimately linked for a long time and to some extent, continue to do so. Springs and rainwater fed an urban population of ruling elites, religious leaders, craftsmen, and merchants. Water storage facilities were strategically placed to maximise supply and demand.
The researchers hope that the exploration of “dhaka” pits in other areas might also reveal how other medieval communities in the region dealt with water management issues.
The article, “Climate-smart harvesting and storing of water: The legacy of dhaka pits at Great Zimbabwe,” by Innocent Pikiray, Federica Sulas, Bongumenzi Nxumalo, Munyaradzi Elton Sagiya, David Stott, Søren M. Kristiansen, Shadreck Chirikure and Tendai Musindo, appears in Anthropocene:
Here is the article’s abstract:
Understanding past water management is crucial to address contemporary human-environmental challenges in sub-Saharan Africa, where urban growth is impacting upon water availability and supply. This study integrates soil profiles, high-resolution topographic data, historical sources, and socioecological memory to reconstruct how the ancient urban society at Great Zimbabwe negotiated water security.
New evidence shows for the first time that closed depressions known as dhaka pits were used by the inhabitants of Great Zimbabwe for water storage and harvesting for a long time, possibly since the emergence of settlement in the mid-second millennium CE.
These pits were part of a landscape-scale water management system that exploited catchment hydrology and groundwater by means of artificial dhaka reservoirs, wells, and springs to secure water for subsistence, farming, ritual and ceremony services.
This study highlights the need for precise dating of the construction and functioning period of this water management system at Great Zimbabwe.
Understanding past water management in such a water-scarce region is important for reconstructing how the ancient Great Zimbabwe urban society negotiated water security, but also for understanding contemporary human-environmental challenges.–medievalists.net.