The second century CE Roman watermills of Barbegal: Unraveling the enigma of one of the oldest industrial complexes

Roman aqueduct maintenance in the water supply system of Divona, France

Carbonate deposits formed in Roman aqueducts provide a window onto the environment and water management in antiquity. These laminated archives precipitated over a period of decades to centuries and are a potential high-resolution source of unwritten history. However, their use as environmental archives is hampered by local and partial removal during maintenance work in some aqueducts. This apparent problem, however, creates a unique opportunity to study Roman water management. We present the discovery of traces of regular maintenance in carbonate deposits of the Roman aqueduct of Divona (Cahors, France). The main objective of this study is to determine the periodicity of local carbonate removal and repairs in this aqueduct. Traces such as tool marks, calcite deformation twins, debris from cleaning and repairs are attested in the deposits as proof of periodic manual carbonate removal by Roman maintenance teams. The δ18O profile, recording at least 88 years of deposition, shows that maintenance work was done at intervals of 1-5 years. The undisturbed periodicity of the δ18O profile indicates that work was carried out rapidly and never in summer, consonant with the advice of the Roman author Frontinus about maintenance of the aqueducts of the city of Rome. Maintenance intervals lengthened and cleaning became less frequent close to the final years of the aqueduct. This change in maintenance policy gives insight into changing local population and socio-economic dynamics in late antiquity.

Sustainable and Regenerative Development of Water Mills as an Example of Agricultural Technologies for Small Farms

Nowadays, the reuse of built agricultural/industrial heritage has been a common practice worldwide. These structures represent excellent symbols of the great agricultural/industrial past. These agricultural/hydro-technologies also serve as monuments of socio-cultural identities, especially in rural areas and on small farms. One example of a successful application of agricultural technologies for small farms is the water mill. By harnessing the water energy, they were used for traditional flour and other goods production (e.g., olive oil) and works requiring energy, with the main role in the evolution of the traditional/cultural landscape. Water mills have been used to drive a mechanical process of milling, hammering, and rolling and are a portion of the agricultural, cultural, and industrial heritage. For approximately two millennia, the vertical mill water wheel prepared the initial source of mechanical power in many regions of the world. Water mills were the first device that converted natural resources of energy into mechanical energy in order to operate some form of machinery. The preservation/management of water mills is challenging due to their long-term abandonment and the lack of information/knowledge about their value. The other obstacles that are faced in their retrofitting and/or preservation are the lack of sufficient economic incentives and complex authorizations/legislations. Sustainability and regeneration of water mills through the centuries are then reviewed for history and agricultural/industrial “archaeology”. The history of water-powered mills in prehistoric and historic times, including ancient Persia/Iran, ancient China, ancient India, the Islamic world, Venetian Crete, medieval Europe, America, and finally present times, is discussed. The outcome of this review allows the understanding of the importance of conservation, optimization, and development of water mills. It will help to know more and achieve sustainable/regenerative development for small farms with respect to water and energy crises at present and in the future.

Travertine crystal growth ripples record the hydraulic history of ancient Rome's Anio Novus aqueduct

Travertine crystal growth ripples are used to reconstruct the early hydraulic history of the Anio Novus aqueduct of ancient Rome. These crystalline morphologies deposited within the aqueduct channel record the hydraulic history of gravity-driven turbulent flow at the time of Roman operation. The wavelength, amplitude, and steepness of these travertine crystal growth ripples indicate that large-scale sustained aqueduct flows scaled directly with the thickness of the aqueous viscous sublayer. Resulting critical shear Reynolds numbers are comparable with those reconstructed from heat/mass transfer crystalline ripples formed in other natural and engineered environments. This includes sediment transport in rivers, lakes, and oceans, chemical precipitation and dissolution in caves, and melting and freezing in ice. Where flow depth and perimeter could be reconstructed from the distribution and stratigraphy of the travertine within the Anio Novus aqueduct, flow velocity and rate have been quantified by deriving roughness-flow relationships that are independent of water temperature. More generally, under conditions of near-constant water temperature and kinematic viscosity within the Anio Novus aqueduct channel, the travertine crystal growth ripple wavelengths increased with decreasing flow velocity, indicating that systematic changes took place in flow rate during travertine deposition. This study establishes that travertine crystal growth ripples such as those preserved in the Anio Novus provide a sensitive record of past hydraulic conditions, which can be similarly reconstructed from travertine deposited in other ancient water conveyance and storage systems around the world.

Reconstructing the hydraulics of the world's first industrial complex, the second century CE Barbegal watermills, France

The Barbegal watermill complex, a unique cluster of 16 waterwheels in southern France, was the first known attempt in Europe to set up an industrial-scale complex of machines during the culmination of Roman Civilization in the second century CE. Little is known about the state of technological advance in this period, especially in hydraulics and the contemporary diffusion of knowledge. Since the upper part of the Barbegal mill complex has been destroyed and no traces of the wooden machinery survived, the mode of operation of these mills has long remained elusive. Carbonate incrustations that formed on the woodwork of the mills were used to reconstruct its structure and function, revealing a sophisticated hydraulic setup unique in the history of water mills. The lower mills used an elbow shaped flume to bring water onto overshot millwheels. This flume was specially adapted to the small water basins and serial arrangement of the mills on the slope. Carbonate deposits from ancient water systems are therefore a powerful tool in archaeological reconstructions and provide tantalizing insights into the skills of Roman engineers during a period of history that is the direct predecessor of our modern civilization.