Page 56 - Urban water supply handbook

URBAN WATER INFRASTRUCTURE: A HISTORICAL PERSPECTIVE

URBAN WATER INFRASTRUCTURE 1.55

Both the systems at Pompeii and Nîmes indicate that water was not distributed
strictly according to function or use, but was distributed based upon the topogra-
phy and geography of the areas served. On the other hand though, the water dis-
tribution systems found in Pompeii and Nîmes were relatively simple compared to
those that existed in Rome. The castellum at Pompeii, located at Porta Vesuvii, is
housed in a large brick building (see Fig. 1.43a), and the aqueduct connects from
the rear of the castellum (see Fig. 1.43b). The plan and elevation of the circular
basin along with the various components that make up the distribution arrange-
ment of the castellum are shown in Fig. 1.44. Water first flowed through two trans-
verse mesh screens (a coarse screen and a fine screen) to remove objects in the
water, after which the water flowed into one of the three channels to the outlets.
The entrance to each channel had a wooden gate, none of which still exist; how-
ever, the bronze fastenings do exist (Hodge, 1992). The three gates were of dif-
ferent heights, with the highest gate on the channel serving the private houses,
hydraulically eliminating their supply first. The lowest gate was on the channel
serving the public fountains, obviously giving them first priority to the water. This
system reflects the principles presented by Vitruvius, but is not the same as
pointed out by Hodge (1992).
From the outlet, water flowed into lead pipes. The center one serving public
fountains had an external diameter of approximately 30 cm; the two outside pipes
had external diameters of approximately 25 cm. Figure 1.45a to e is a group of
photos taken looking into the castellum from the center hole on the outside of the
building housing the castellum. Figure 1.45 a, b, and c are, respectively, photos of
the center channel (for the pipe leading to the public fountains), the left channel
(for the pipe leading to the baths and theaters), and the right channel (for the pipe
leading to the private houses). Note that by referring to Fig. 1.45d it is obvious that
the center channel is placed higher than the other two channels. Figure 1.45e
shows in the background the entrance opening into the castellum.
Hodge (1996) reappraised the castellum divisorium at Pompeii to conclude that
the pipes delivering water to the city were far too large to have been filled by the
small aqueduct. He illustrates that Vitruvius’s description of dividing up the flow
would be mathematically impractical and instead each of the three pipes must have
been filled up one at a time using the sluice gate as the control mechanism, thus insti-
tuting a system of water rationing. The urban distribution system included secondary
castella, mounted on brick piers (see Fig. 1.46) throughout the city, and served as
storage tanks to supply local demand when the main supply was shut off. The taps
found in Pompeii were possibly used to regulate supply. Hodge concluded that this
system may have been peculiar only to Pompeii and should not be taken (as it gen-
erally has been) as the model of standard Roman urban practice.
The castellum at Nîmes, France (see Fig. 1.47a and b), is located on high
ground at the north end of the city. Water entered the circular basin through the
approximately 1.2-m-wide by 1.10-m-high (Hodge, 1992) opening shown in Fig.
1.47a. A sluice gate, located near the outlet opening and consisting of two verti-

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