"By the middle of the 1st century AD Rome had nine aqueducts, which were the subject of a detailed treatise written by the distinguished Roman senator and consul Sextus Julius Frontinus in his capacity as curator aquarum (head of the water board). Only two aqueducts were added in the later empire, bringing the total length to over 450 km (280 miles). It is Frontinus who gives us much of the statistical data usually cited on the aqueducts of Rome, although some of his figures are questionable." From page 235 of The Seventy Wonders of the Ancient World: The Great Monuments and How They Were Built, edited by Chris Scarre, published by Thames & Hudson.
For more information, see the page on Sextus Julius Frontinus at WaterHistory.org.
