Researchers Solve the Ancient “Water” Mystery of the First Large City in Southern Africa

The ruins of the ancient city of Great Zimbabwe. The vegetation around the ruins hides a lot of depressions, so-called Dhaka pits, which until now have been thought to have originated from the excavation of clay. With remote sensing methods and excavations, the researchers have found that the pits must also have been used to store and manage water for the city. Credit: Federica Sulas, Cambridge University

The mystery of how the ancient city of Great Zimbabwe prospered for centuries in a region plagued by droughts has finally been solved.

The ruins of the first major city in southern Africa, Great Zimbabwe, can be found in the mountains of southeastern Zimbabwe. The name “Zimbabwe” translates to “the big stone house” in the Shona language and the country was named after the ancient city. Great Zimbabwe was an 11th-century capital of the Shona kingdom, encompassing parts of present-day Zimbabwe and Mozambique, renowned for its large stone houses and enclosures.

The city flourished and many people lived there 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 the article “Climate-smart harvesting and storing of water: The legacy of dhaka pits at Great Zimbabwe.” 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. However, the new studies show that this may not be the whole truth.

The 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.

The people of Great Zimbabwe thus devised climate-smart methods for storing and managing water in an area that is characterized 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.

It is impressively conceived and shows that, much earlier than previously thought, management of the natural hydrological system was under control in the city. Perhaps they have even managed it so well that other places in the world can now learn something from how they did it hundreds of years ago in Great Zimbabwe.

Reference: “Climate-smart harvesting and storing of water: The legacy of dhaka pits at Great Zimbabwe” by Innocent Pikirayi, Federica Sulas, Bongumenzi Nxumalo, Munyaradzi Elton Sagiya, David Stott, Søren M. Kristiansen, Shadreck Chirikure and Tendai Musindo, 9 December 2022, Anthropocene.
DOI: 10.1016/j.ancene.2022.100357

The study was funded by the South African National Research Foundation (NRF), the World Archaeological Congress Travel Support Committee, and the Danish National Research Foundation Centre of Excellence for Urban Network Evolutions.