In Ancient Rome, the Aqua Alsietina (sometimes called Aqua Augusta) was the earlier of the two western Roman aqueducts, erected somewhere around 2BC, during the reign of emperor Augustus. It was the only water supply for the Transtiberine region (the right bank of the river Tiber). In his chief work, De aquaeductu (written in 97 CE), containing a history and description of the water-supply of Rome, Sextus Julius Frontinus ascribes only a meager volume to the Aqua Alsietina. This makes sense, if the naumachia was no longer in use in his time (second half of the first century CE).