Great Zimbabwe was the first major city in southern Africa, home to an estimated 18,000 people at its peak. Yet no one really knows why it is now in ruins.
The downfall of the once thriving medieval metropolis is sometimes attributed to drought and a drying climatebut archaeologists have now found evidence of careful water protection amidst the rubble.
A team of researchers from Denmark, South Africa, England and Zimbabwe argue that a series of large, circular depressions known as “Dhaka” pits found around the city were not used to excavate clay, experts say once thought, but to catch water.
For example, at the foot of several hills lie numerous dhaka pits, strategically placed to collect rain and groundwater. Other pits around the city straddle creeks.
Researchers argue that by collecting rainwater and blocking off some parts of a river or stream, the people who once lived here may have ensured that water was available for drinking and farming most of the year, even in the dry season .
Many of the plant remains found near Dhakas, for example, are known to thrive near rivers or groundwater sources that contain high levels of soil moisture.
The new perspective of Great Zimbabwe’s Dhaka pits was made possible through the use of airborne laser scanning to survey key features of the site, even in locations with dense vegetation.
These results were then supplemented by soil surveys and discussions with local communities who also need to conserve water in the arid region.
Figuring out how much water all the dhakas in the city could have once held is an inaccurate work, especially since this is one of the first studies to really examine the structures. Still, estimates suggest these pits could have stored over 40 million gallons of water.
In Great Zimbabwe’s heyday, between the 11th and 15th centuries, the city was home to ruling elites, religious leaders, artisans and merchants, all of whom would have shared spring and rainwater in an integrated and flexible system.
Experts say that during the rainy season, some areas of the city would have become wet and swampy. These places seem to have been perfect for quarrying clay to build houses. In drier times, some of these quarries appear to have been converted into reservoirs to collect groundwater and runoff from the surrounding hills.
“This partially engineered landscape, although relatively passively organized, required maintenance as runoff was allowed to flow into these basins,” the authors said to write.
“Taken together, the new record shows that water’s physical forms, ecological functions and cultural values were all shaped and shaped by how communities interacted with, managed and conserved water,” they said Add.
Today very little is known about the history of Great Zimbabwe. It’s still possible that the city collapsed due to climate changeeven with such a carefully tuned water system.
During their existence, the world witnessed the Medieval climate anomaly and a Little Ice Age, which could have put the growing city under enormous stress. But economic or political strains could also have caused its downfall.
More research needs to be done before archaeologists can say what happened to the first city in southern Africa and its inhabitants. Perhaps there is a lesson to be learned in the ruins.
The study was published in anthropocene.
