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Abstract

Travertine crystal growth ripples are used to reconstruct the early hydraulic history of the Anio Novus aqueduct built in AD 38-52 at Roma Vecchia in ancient Rome. These crystalline travertine morphologies deposited within the aqueduct channel record the hydraulic history of gravity-driven turbulent flow at the time of Roman operation. Travertine deposits preserved within ancient aqueduct channels record information about the hydrology, temperature, and chemistry of the flowing water from which they precipitated. However, travertine is also chemically reactive and susceptible to freshwater diagenesis, which can alter its original composition and impact reconstructions of aqueduct operation, maintenance, and climate. Hydraulic reconstructions in combination with a suite of high-resolution optical, laser, electron, and x-ray microscopy analyses, have been used to determine the original crystalline structure and diagenetic alteration of travertine crystal growth ripples deposited in the Anio Novus aqueduct. 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. This study establishes that travertine crystal growth ripples such as those 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.