vitruvius on water and aqueducts

In  Pompeii, A Novel,  Marcus Attilius Primus, the aquarius of the Aqua Augusta, recalls in his mind what he has learned studying Vitruvius, the famous architect/scholar, when he is planning to repair the broken Augusta.

Here is Vitruvius (On Architecture via Lacus Curtius), BookVIII, On Water.  Scroll down to Chapter 6.

1. Water is conducted in three ways, either in streams by means of channels built to convey it, in leaden pipes or in earthen tubes, according to the following rules.  If in channels, the structure must be as solid as possible, and the bed of the channel must have a fall of not less than half a foot to a length of one hundred.  These channels are arched over at top, that the sun may strike on the water as little as possible.  When they are brought home to the walls of the city a reservoir (castellum) is built, with a triple cistern attached to it to receive the water.   Read on

There are two print versions of On Architecture, Ten Books on Architecture and the Loeb editions in two books, On Architecture, Books I-V & On Architecture, Books VI-X.