Roman aqueduct
Rome's first aqueduct was built in 312 BC, and supplied a water fountain at the city's cattle market. By the 3rd century AD, the city had eleven aqueducts, sustaining a population of over a million in a water-extravagant economy; most of the water supplied the city's many public baths. Cities and towns throughout the Roman Empire emulated this model, and funded aqueducts as objects of public interest and civic pride, "an expensive yet necessary luxury to which all could, and did, aspire".
Cura Annonae
A steady supply of water was needed for watermills and this came from the Aqua Traiana, an aqueduct bringing water some from springs near Lake Bracciano to Janiculum hill just outside the walls of the city of Rome. The aqueduct was inaugurated in 109 CE and the water it carried was used initially as drinking and bathing water. A famine (and resultant riots) in 190 CE caused by corruption in the grain distribution system influenced the Roman government under Emperor Septimus Severus to intervene and convert the distribution of grain to the populace into the distribution of flour. The watermills constructed at Janiculum "were intended to centralize, regularize, and perhaps even deprivatize the city's milling operations." Estimates of the date when the watermills came into operation vary, but it was probably in the early 3rd century.