(ORDO NEWS) — The largest medieval city in South Africa used dozens of large tanks to store water. A new study shows how this system allowed the community to manage a stable water supply in a region with a challenging climate.
Great Zimbabwe is a complex of stone structures, covering an area of 24 hectares and located in the mountains in the southeast of Zimbabwe. It is one of the few medieval cities in sub-Saharan Africa and the largest among them.
According to modern ideas, the city was founded in the 9th century AD. Its builders and population are the Shona people of the Bantu group.
The very word Zimbabwe means “big stone house” in the Shona language, and the country takes its name from the ancient city.
By the 11th century, it had become the capital of the Shona Kingdom (sometimes referred to as Monomotapa), which controlled parts of present-day Zimbabwe and Mozambique.
The city, with a population of ten to 18 thousand people, prospered until it was abandoned in the 17th century for unknown reasons.
But how did the people who lived in it meet their needs? Water was a particular challenge: Greater Zimbabwe is located in an area with frequent droughts, so ensuring a stable supply of water for so many people and the number of livestock they needed must have been a challenge.
In such an area, nomads can usually survive, but not townspeople who are tied to one place.
Moreover, in the religious cults of modern Shona, worship of the god of water and requests for rain are one of the central elements. But did prayers help their medieval ancestors, or did they use other methods?
Using remote sensing and excavation methods, they explored a series of large depressions in the landscape, which the locals call “dhaka” (dhaka).
These depressions were not previously studied, as it was believed that they were dug only to collect clay used in construction in the city.
New research shows that the pits were also used to store and distribute water in the city. There are clear indications that depressions were dug where they could collect surface water while at the same time seeping groundwater into them. In them, the water was in the dry periods of the year.
The authors of the work found more dhaka holes than previously known. They were found where small streams naturally form after rain, or where groundwater comes to the surface.
This, combined with the location and design of the depressions, convinced researchers that the dhaka pits functioned as an elaborate system to provide a stable water supply outside of the rainy season. Scientists estimate that the system could store 18,000 cubic meters of water.
Thus, the people of Greater Zimbabwe have developed methods for storing and managing water in an area that is characterized by three distinct climatic seasons: very warm and dry, warm and wet, and finally warm and dry winters.
Such water supply was simply necessary for the creation of an urban society that needed a safe supply of water for its inhabitants, livestock and agriculture.
“Despite fragmentation, a growing body of ecological and archaeological data, combined with historical and ethnographic information, paints a new, compelling portrait of Greater Zimbabwe: a landscape where human settlement, land and water have been closely linked for a long time and to some extent continue to do so.
Springs and rainwater fed the urban population, which consisted of the ruling elite, religious leaders, artisans and merchants. The reservoirs were strategically located to meet the demand for water as much as possible,” the authors of the work said.
The researchers hope that studying dhaka pits in other areas may also show how other medieval communities in the region dealt with water management issues.
Previously, other scientists suggested that the abandonment of Greater Zimbabwe in the 17th century (and the disappearance of large cities in southern Africa while preserving the Shona people) is the result of a long-term decrease in precipitation in the region due to global cooling (the Little Ice Age).
If this is so, then it can be assumed that the system of water storage tanks was sufficient only to compensate for one or two dry seasons, but not to switch the climate to a new, colder and drier state.
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