Roman Aqueducts

The Roman Aqueducts
An Engineering Wonder

sabato 2 febbraio 13

What have the Romans ever done for us?

Monty Python
Life of Brian, 1979

https://www.youtube.com/watch?v=ExWfh6sGyso


Before the Romans

Rome and Water

How the Romans Built Aqueducts

Lessons Learned

Appendix


Water is essential to Life and the
Development of Civilization

Drinking

Agricolture

Sanitation

Transportation

Energy


The First Civilizations appeared near abundant,
easily accessible Water Supplies

Ancient Egypt (The
Nile)

Mesopotamia (Tigris &
Eufrates)

India (Indus)


Water needs to be managed

Control Inundations

Distribute Fresh Water

Collect waste waters
Aqueduct in Segovia (Spain)

Nilometer

Cloaca Maxima


Fresh water supply is essential especially in dry regions.
Other civilizations built water transportation systems,
before the Romans

A qanat (Arabic ) or kareez (Persian) is a water
management system used to provide a reliable supply
of water to human settlements or for irrigation in hot,
arid and semi-arid climates.

The qanat technology was used most extensively in
areas with the following characteristics:
Water Table

An absence of larger rivers with year-round ﬂow
sufﬁcient to support irrigation.
Proximity of potentially fertile areas to
precipitation-rich mountains or mountain ranges.
Arid climate with its high surface evaporation rates
so that surface reservoirs and canals would result
in high losses

An aquifer at the potentially fertile area which is
too deep for convenient use of simple wells.


The Qanat taps underground water and transports it
using gravity. The underground course avoids loss by
evaporation
The investment and organization required by the construction and the maintenance of a
qanat is typically provided by local merchants or landowners in small groups.

The qanat system has the advantage of being relatively immune to natural disasters
(earthquakes, floods…) and human destruction in war. Further it is relatively insensitive to
the levels of precipitation; a qanat typically delivers a relatively constant flow with only
gradual variations from wet to dry years.

A typical town has more than one qanat. Fields and gardens are located both over the
qanats a short distance before they emerge from the ground and after the surface outlet.
Water from the qanats defines both the social regions in the city and the layout of the city.

The water is freshest, cleanest, and coolest in the upper reaches and more prosperous
people live at the outlet or immediately upstream of the outlet. When the qanat is still below
grade, the water is drawn to the surface via Ater-wells or animal driven Persian wells.

The lower reaches of the canals are less desirable for both residences and agriculture. The
water grows progressively more polluted as it passes downstream. In dry years the lower
reaches are the most likely to see substantial reductions in flow.


The construction method of the qanat is similar to that
of the aqueduct

Construction of a qanat is usually performed by a crew of 3-4 muqannis.
For a shallow qanat, one worker typically digs the horizontal shaft, one
raises the excavated earth from the shaft and one distributes the
excavated earth at the top.

The excavated material is usually transported by means of leather bags up
the vertical shafts. It is mounded around the vertical shaft exit, providing a
barrier that prevents windblown or rain driven debris from entering the
shafts. From the air, these shafts look like a string of bomb craters.

Traditionally qanats are built by a group of skilled laborers, muqannis, with
hand labor. The profession historically paid well and was typically handed
down from father to son.

The critical, initial step in qanat construction is identiﬁcation of an
appropriate water source.

The muqannis follow the track of the main water courses coming from the
mountains or foothills to identify evidence of subsurface water such as
deep-rooted vegetation or seasonal seeps.


Key facts

Vertical shafts are excavated along the route, separated at a distance of 20-35 m.
In general, the shallower the qanat, the closer the vertical shafts.

Most qanats in Iran run less than 5 km. The overall length of the qanat often runs
up to 16 km, while some have been measured at ~70 km in length near Kerman.

The vertical shafts usually range from 20 to 200 meters in depth, although in Iran
qanats in the province of Khorasan have been recorded with vertical shafts of up
to 275 m. The vertical shafts support construction and maintenance of the
underground channel as well as air interchange. Deep shafts require intermediate
platforms to simplify the process of removing spoils.

The qanat's water-carrying channel is 50-100 cm wide and 90-150 cm high. The
channel must have a sufﬁcient downward slope that water ﬂows easily. In shorter
qanats the downward gradient varies between 1:1000 and 1:1500, while in longer
qanats it may be almost horizontal. Such precision is routinely obtained with a
spirit level and string.

The construction speed depends on the depth. At 20 meters depth, a crew of 4
people can excavate a horizontal length of 40 meters per day. When the vertical
shaft reaches 40 meters, they can only excavate 20 meters horizontally per day
and at 60 meters in depth this drops below 5 horizontal meters per day. Deep,
long qanats (which many are) require years and even decades to construct.


Qanats are also used in clever air conditioning systems
called “Wind Catchers”
First, a windcatcher is capped and has several directional ports at the top
(T raditionally four). By closing all but the one facing away from the incoming wind, air
is drawn upwards using the Coanda effect, similar to how opening the one facing the
wind would push air down the shaft.

The key to generating frigid temperatures seems to be that there are very few cracks
at the base of the thick structure below, but there is a signiﬁcant air gap above the
qanat. The qanat below aggregates the cold, sinking air of the night, which is then
trapped within, unable to rise up to the less dense surface air. A windcatcher can
create a pressure gradient which sucks at least a small amount of air upwards through
a house. This cool, dry night air, being pulled over a long passage of water,
evaporates some of it and is cooled down further.

When coupled with thick adobe that exhibits high heat transmission resistance
qualities, the windcatcher is able to chill lower level spaces in mosques and houses
(e.g. shabestan) in the middle of the day to frigid temperatures.

So effective has been the windcatcher in Persian architecture that it has been
routinely used as a refrigerating device (yakhchal) for ages. Many traditional water
reservoirs (ab anbars) are built with windcatchers that are capable of storing water
and even ice collected during the winter at near freezing temperatures for months in
summer.

High humidity environments destroy the evaporative cooling effect enjoyed in the dry
conditions seen on the Iranian plateau;


The technology is known to have developed in ancient Persia, and then
spread to other cultures, especially after the Muslim conquests, to the
Iberian peninsula, southern Italy and North Africa
Written records leave little doubt that ancient Iran
(Persia) was the birthplace of the qanat.

As early as the 7th century BC, the Assyrian king Sargon
II reported that during a campaign in Persia he had found
an underground system for tapping water. His son, King
Sennacherib, applied the "secret" of using underground
conduits in building an irrigation system around Nineveh.

During the period 550-331 BC, when Persian rule
extended from the Indus to the Nile, qanat technology
spread throughout the empire.

The Achaemenid rulers provided a major incentive for
qanat builders and their heirs by allowing them to retain
proﬁts from newly-constructed qanats for ﬁve
generations.

During Roman-Byzantine era (64 BC to 660 AD), many
qanats were constructed in Syria and Jordan. From here,
the technology appears have to diffused north and west
into Europe.


Palermo, in Sicily, is the home of qanats built during the
arab domination
In the early ages (Punic and Roman times) wter supply came from wells and natural springs just outside the city

In the IXth century the growth of the city as a capital under arab rule sharply increased water needs for private and public use
(hammam)

Arabs resolved the problem importing and adapting the qanats technology. In Palermo there no single supply well tapping into
the water bed but a “drainage gallery” were water seeps up to be gently conveyed downhill, with a less than 0,5% incline

There were two types of wells along the course: those used to excavate the qanat and for maintenance, and others, larger,
used to lift up the water using “persian wheels”, sometimes driven by animals. In coincidence of these wells the bottom of the
qanat formed a “pool”.

Arabs introduced also the “wind-catcher” technology, applied in various “Camere dello Scirocco”

Borgata Villagrazia Qanat dell’Uscibene- Altarello “Scirocco’s Room
Villa Naselli, Galleria
della Sorgente di Baida (Palermo) Villa Savagnone - Altarello di Baida (PA)


Although famously associated with the Romans, aqueducts were
devised much earlier in the Near East and Indian subcontinent, where
peoples such as the Egyptians built sophisticated irrigation systems.

Roman-style aqueducts were used as early as the 7th century
BC, when the Assyrians built a limestone aqueduct 30 feet (10 m)
high and 900 feet (300 m) long to carry water across a valley to
their capital city, Nineveh. The full length of the aqueduct ran for
50 miles (80 km).In the new world, when the Aztec capital of
Tenochtitlán was discovered in the middle of the second
millennium, it was watered by two aqueducts.

India:The Indian subcontinent witnessed the construction of
some of the earliest aqueducts. Prominent evidence can be
found at the sites of present day Hampi. The massive aqueducts
near river Tungabhadra supplying irrigation water were once
15 miles (24 km) long[2]. The elegant water ways were designed
to supply water to royal bath houses

The Phoenicians are the most important among pre-classical Hampi, India
engineers. In Cyprus water was supplied to temples by rock-cut
subterranean conduits carried across intervening valleys in
siphons. Such conduits have been found near Citium, Amathus,


The numerous conduits which have supplied Jerusalem probably go
back to the times of the kings of Judah
The principal reservoir consists of the three Pools of Solomon
which supplied the old aqueduct. These pools collected the water
from Ain Saleh and other springs, and sent it to the city by two
conduits. The higher of these--probably the older--was partly a
rock-cut canal, partly carried on masonry; the siphon-pipe system
was adopted across the lower ground near Rachel's T omb, where
the pipe (15 in. wide) is formed of large pierced stones embedded
in rubble masonry.

The lower conduit is still complete; it winds so much as to be
altogether some 20 miles long. Near the Birket-es-Sultan it passes
over the valley of Hinnom on nine low arches and reaches the city
on the hill above the Tyropeon valley.

In the case of the underground tunnel which brought water from
the Virgin's Fountain to the pool of Siloam, the two boring parties
had no certain means of keeping the line; there is evidence that
they had to make shafts to discover their position, and that
ultimately the parties almost passed one another. Though the
direct distance is 1100 ft., the length of the conduit is over 1700 ft.
Besides these conduits excavation has discovered traces of many
other cisterns, tunnels and conduits of various kinds. Many of
them point to periods of great prosperity and engineering
enterprise which gave to the city a water-supply far superior to
that which exists at present.


The earliest attempts in Europe to solve the problems of water-supply
were made by the Greeks, who perhaps derived their ideas from the
Phoenicians
Among the earliest examples of Greek work are the tunnels or
emissaria which drained Lake Copais in Boeotia; these, though not
strictly aqueducts, were undoubtedly the precursors of such
works, consisting as they did of subterranean tunnels (ὑπονομοι)
with vertical shafts (φρεατιαι), sixteen of which are still
recognizable, the deepest being about 150 ft.

The insufficiency of water, supplied by natural springs and cisterns
hewn in the rock, which in an early age had satisfied the small
communities of Greece, had become a pressing public question by
the time of the Tyrants, Polycrates of Samos obtained the services
of Eupalinus, an engineer celebrated for the skill with which he had
carried out the works for the water-supply of Megara (c. 625
B.C.).

At Samos the difficulty lay in a hill which rose between the town
and the water source. Through this hill Eupalinus cut a tunnel 8 ft.
broad, 8 ft. high and 4200 ft. long, building within the tunnel a
channel 3 ft. broad and 11 ells deep. The water, flowing by an
accurately reckoned declivity, and all along open to the fresh air,
was received at the lower end by a conduit of masonry, and so led
into the town, where it supplied fountains, pipes, baths, cloacae,
&c., and ultimately passed into the harbour (Herod, iii. 60).


Break Down of Water Allocation in Augustus’ Rome

Lacus: Public Basins

Munera (Display Fountain and Water games)
Private; 32%

Public; 53% Opera Publica: Construction and
maintenance of public buildings including
Ceasar's; 15% Termae

Camps

Public: Castra, Opera publica, munera, Lacus
For General public use, included water made available in public basins for domestic use of “insulae”
dwellings
Private:
Carried into private properties, usually rich/noble people Villae or Domus
In nomine Caesaris:
it is not clear on what principles water was distributed in nomine Caesaris – does this refer to
distribution to the emperor’s properties (and those of the imperial family), or to other public or
military destinations, or also to private individuals to whom the emperor had granted privileges?

Source: Frontinus, De Aquaeductu Urbis Romae


It is Frontinus who gives us an idea
of how water was used in Rome

Uncertainties:
Deﬁnition of Castra and Castellum
What is included in Ceasar’s Name


ATotal of 11 Aqueducts were built to
serve the Capital City of Rome


Organizing the data on a scatter chart
reveals a pattern...
100
90
Trajana
Elevation arriving in Rome

80
Claudia
70 T Julia
epula Anio Novus
60 Marcia
Anio Vetus
50 Alexandrina
40
30
Virgo
20 Alsietina
Appia
10
0
‐400 300 b.c. ‐200 100 b.c.
‐300 ‐100 0 100 a.d.
100 200 300 a.d.
300


With some exception, each new aqueduct
arrived in Rome at a higher elevation
100
90
Trajana

80
Claudia
70 T Julia
epula Anio Novus
60 Marcia
Anio Vetus
50 Alexandrina
40
30
Virgo
20 Alsietina
Appia
10
0
‐400 300 b.c. ‐200 100 b.c.
‐300 ‐100 0 100 a.d.
100 200 300 a.d.
300


This “correlation” is even stronger not
condidering the two “outliers”
90

80

70

60

50

40

30

20
Virgo
Alsietina
10

0
‐400 300 b.c.
‐300 ‐200 100 ‐100
b.c. 0 100 a.d.
100 300 a.d.
200 300


Aqua Appia, the ﬁrst aqueduct built in 312 b.c., originally served the entire city.
It was followed over the next three centuries by the Anio Vetus, the Aqua Marcia,
Tepula, Julia, and Virgo

As a result of this increase in availability, it was no longer
necessary for the Aqua Appia to supply all districts with water
in the Augustan age. Frontinus provides us with a list of the
wards served by each aqueduct, and it seems likely that the
Appia’s distribution was refocused to serve the areas closest to
its distribution point, particularly the Aventine and the Circus
Maximus


Six aqueducts provided water to districts inside the
city in the last years of Augustus’ reign

Quinaria: Unit of measure for water ﬂow:
1 Quinaria=0,48 liter/sec
1 Quinaria=41,5 MQ/day

Source: C. Di Fenizio, Sulla portata degli antichi acquedotti romani
e determinazione della quinaria, Roma, 1916


Growth in Water Availability mirrored
growth in population
1.600.000
Water Supply (Cubic Meters/day)

1.400.000
1500000

1.200.000

950000
1.000.000

800.000

600.000

400.000
Population

200.000
187000
30.000
0
312 b.c.
269 b.c.
140 b.c.
125 b.c.
33 b.c.
19 b.c.
2 a.d.
52 a.d.
109 a.d.
226 a.d.

Appia
Anio Vetus
Marcia
Tepula
Julia
Virgo
Alsientina
Claudia + Anio Novus
Traiana
Alexandrina


The availability of water was abundant even for today’s
standards

600,0

500,0
Cubic Meters/Year

400,0

300,0

200,0

100,0

,0
Republic
Augustus
Imperial
Milan
Rome
Torino

Per Capita Per Capita
Availability Domestic Consumption
Ancient Rome Contemporary


Aqueducts were often “celebrated” in coins
The sestertius reading IMP CAES NERVAE TRAIANO AVG GER
DAC P M TR P COS V PP in capitals representing the bust of emperor
Traian (98 - 117 AD) looking to the right. During his reign both the
aqueduct Aqua Traiana and the Baths of Traian were put into use.
The text on the reverse reads SPQR OPTIMO PRINCIPI AQVA
TRAIANA S C with an image that can be interpreted in different ways:
the genius of the aqueduct, an image of the castellum aquae (the water
Trajana distribution station) at the end of this Roman aqueduct, or a collection
of general elements of the water supply of Rome.

It was 60 years later - about 56 bc - that moneyer L. Marcius Philippus
honored Q. Marcius Rex with a coin bearing the image of 'his'
aqueduct, the Aqua Marcia. The reverse side shows an equestrian
statue based on ﬁve arches reaching to the rim and the name of the
moneyer PHILIPPVS. Within the arches one reads AQVA MR (Aqua
Marcia). One assumes that here the builder Q Marcius Rex is
Marcia represented together with the aqueduct which is named after him.
Note that the moneyer also belongs to the Marcia family.

This nymphaeum is an ornamental fountain including a castellum (water
distribution station) which was fed by a branch of the Aqua Julia
aqueduct It is the only remaining example in Rome of a class of
fountains which is called 'munera' by Frontinus because of its double
function (ornamental fountain and water distribution station). The coins
may have been mint when the Aqua Alexandrina was put into use.


Arches are the ﬁrst things that comes to mind when
thinking about aqueducts...

Pont du Gard, near Nimes in France Aqua Appia


...but most of the lenght of an aqueduct ran
underground
Lenght (Km)
Anio Novus

Aqua Claudia

Aqua Alsie?na

Aqua Virgo

Aqua Julia

Aqua Tepula

Aqua Marcia

Anio Vetus

Aqua Appia

0 10 20 30 40 50 60 70 80 90 100 Nimes Aqueduct.
Total Lenght Specus height 170 cm
Aqua Marcia Underground Lenght

in Vicovaro, near Rome


Most Aqueducts had certain key components

Construction & Inspection Wells
Castle
Inverted
Piscina (Water
Source Basement Syphon
Specus Arches Limaria Tower)
Fistule

Watch Out!
This design is an oversympliﬁed example
1) Underground section covers 90/95% of total lenght
2) Arches are more common near the city than upstream


In Roman aqueducts water moved mostly by gravity. In
modern conduits it moves only by pressure

Note:
Pressurized inverted syphons were used only
occasionally, to bridge minor gaps. Technology did not
allow for high pressures


Organization of Building aqueducts
Considering the amount of surveying, underground building, and bricklaying involved, a
construction of this size could not be built all at once. Instead, the engineers divided the
entire construction site into individual building areas.
Through archaeological research, the boundaries of these building areas have been
determined. It has further been demonstrated that the surveying took place separately
from the building, as is in fact the rule today in large construction projects.

Finding the spring
Deciding the Route
Getting the water
Digging the Tunnels
The Inverted Syphon
The Viaducts
The settling Basin
The Castellum
Domestic Use


Finding Water

-springs
-observing vapours rising at sunrise
-nature of the place (clay,, black earth, gravel, red
sands, red stone)
- presence of certain vegetation (bulrush, the wild
willow, the alder, the withy, reeds, ivy, and other
plants of a similar sort, which neither spring up nor
ﬂourish without moisture)


Finding Water - Vitruvius Advice
Marcus Vitruvius Pollio, a Roman architect and engineer, in the first century B.C. wrote his influential treatise
entitled The T Books on Architecture, Vitruvius provided specific instructions on finding and selecting
en
springs to provide houses with water:

This will be easily accomplished if the springs are open and flowing above ground. If that be not the case, their sources under ground are
to be traced and examined. In order to discover these, before sunrise one must lie down prostrate in the spot where he seeks to find it,
and with his chin placed on the ground and fixed, look around the place; for the chin being fixed, the eye cannot range upwards
farther than it ought, and is confined to the level of the place. Then, where the vapours are seen curling together and rising into the
air, there dig, because these appearances are not discovered in dry places.
We should also consider the nature of the place when we search for water. In clay, the vein of water is small, the supply little, and not of the
best flavour; and if in low places, it will be muddy and ill tasted. In black earth, only tricklings and small drops are found, which,
collected from the winter rain, subside in compact hard places, and are of very excellent flavour. In gravel, the veins are small and
variable, but they are exceeding well flavoured. In the strong, common and red sands, the supply is to be depended on with more
certainty, and is of good taste. In red stone, abundance and that of good quality may be obtained, if it do not filter away and escape
through the pores. At the feet of mountains, and about flinty rocks the supply is copious and abundant; it is there cold and more
wholesome. In champaign countries, the springs are salt, gross, tepid, and unpleasant, except those, which percolating from the
mountains beneath the surface, issue forth in the plains, where, especially when shadowed by trees, they are as delicious as those of
the mountains themselves.
3. Besides the above signs for ascertaining in what places water may be found, are the following: when a place abounds with the slender
bulrush, the wild willow, the alder, the withy, reeds, ivy, and other plants of a similar sort, which neither spring up nor flourish without
moisture. For these plants usually grow about lakes, which, being lower than the other parts of a country, receive both the rain water
and that of the district, through the winter, and, from their size, preserve the moisture for a longer period. On these, however, we must
not rely. But in those districts and lands, no lakes being near, where the plants in question grow spontaneously, there we may search.


Choosing the Spring - Vitruvius Advice
Springs should be tested and proved in advance in the following
Expertiones autem et probationes eorum sic sunt providendae. si
ways. If they run free and open, inspect and observe the
erunt profluentes et aperti, antequam duci incipiantur,
physique of the people who dwell in the vicinity before
aspiciantur animoque advertantur qua membratura sint qui
beginning to conduct the water, and if their frames are
circa eos fontes habitant homines, et si erunt corporibus
strong, their complexion fresh, legs sound, and eyes clear,
valentibus coloribus nitidis, cruribus non vitiosis, non lippis
the spring deserves complete approval.
oculis, erunt probatissimi. item si fons novus fossus fuerit et in
vas corinthium sive alterius generis quod erit ex aere bono ea
If it is a spring just dug out, its water is excellent if it can be
aqua sparsa maculam non fecerit, optima est. itemque in
sprinkled into a Corinthian vase or into any other sort made
aeneo si ea aqua defervefacta et postea requieta et defusa
of good bronze without leaving a spot on it. Again, if such
fuerit neque in eius aenei fundo harena aut limus invenietur, ea
water is boiled in a bronze cauldron, afterwards left for a
aqua erit item probata.
time, and then poured off without sand or mud being found
2. item si legumina in vas cum ea aqua coniecta ad ignem posita
at the bottom of the cauldron, that water also will have
celeriter percocta fuerint, indicabunt aquam esse bonam et
proved its excellence.
salubrem. non minus etiam ipsa aqua quae erit in fonte si fuerit
limpida et perlucida, quoque pervenerit aut profluxerit muscus
And if green vegetables cook quickly when put into a vessel of
non nascetur neque iuncus, neque inquinatus ab aliquo
such water and set over a fire, it will be proof that the water is
inquinamento is locus fuerit sed puram habuerit speciem,
good and wholesome. Likewise if the water in the spring is
innuitur his signis esse tenuis et in summa salubritate.
itself limped and clear, if there is no growth of moss or reeds
where it spreads and flows, and if its bed is not polluted by
filth of any sort but has a clean appearance, these signs
indicate that the water is light and wholesome in the highest
degree.1


There are many ways to get (ground)water into an aqueduct. Springs
were the commonest source for roman aqueducts. River intakes were
used occasionally.
Spring boxes and Well intakes
Collect water in a rectangular chamber; the water was
supplied through numerous splits or specially created,
sometimes arched, openings. A single outlet discharges the
water into the aqueduct conduit.

Infiltration galleries
Infiltration galleries were sections of aqueduct gallery, 20 -
100 m long which ran along a hill side to intercept the flow
of water that trickled out of the splits in the wall into the
gallery. At one side the water was collected into a settling
basin to get rid of the debris and sediments: the start of
the aqueduct.

River intakes
A river as a source for an aqueduct was not very popular in
Roman times

Dams
Artificial created lakes as a source were rare although they
could have been used to equilize the variations in the
seasonal flow rates of the feeding spring(s)


While different in shape, spring boxes shared the purpose of
protecting the water source

Bingen (Germany) Kalmuth, Cologne (Germany) Emmaus / Nicopolis (Israel)

Spring Boxes often included a settling basin


Infiltration Galleries could be built into a web of tunnels
for better yield

Different types of infiltration Grune Putz, Germany
Sens (France)
areas in one system, Gigen (infiltration galleryand
(Bulgaria settling basin)


River intakes led usually to poor quality of water, dependent on meteo
conditions. The Anio Vetus waters muddied each time it rained

Alcabideque, start of the Conimbriga aqueduct (Portugal)


Dams were sometimes built to improve water quality (acting as settling
basin) and to stabilize the seasonal water flow

Emperor Nero (AD 54-68) had a 40 m high, 13.5 m wide, and 80 m long dam built for a pleasure lake near his villa at Subiaco,
Italy. The dam was one of the earliest Roman dams and remained the highest the Romans ever built. Moreover, the Subiaco dam
and two smaller dams nearby are the only Roman dams in Italy. Although the dam was too thin, it remained intact until it failed
in 1305. Records blace the blame on two monks who took it upon themselves to remove stones from the dam, apparently in an
attempt to lower the level of the lake which was flooding their fields.

Inside a monastary near the dam hangs a painting from 1428 showing St. Benedict fishing from the crest of the Subiaco Dam.
Incedentally, this painting is the oldest surviving illustration of a dam.

he record height of the Roman Subiaco dam wasn't broken until 1594 with the construction of the 46 m high Tibi dam in Spain.
However, the Roman concept of a rectangular wall was mostly maintained, with only a few, hesitant attempts to use trapezoidal,
let alone the correct triangular, cross sections. The use of concrete by the Romans for the dams' interior or as a building material
in general, fell into oblivion, while the construction techniques essentially remained the same: pick and shovel.

Sant Bemedict fishing from the dam


Roman gravity dams abound in the Iberian peninsula, North Africa, and
the Middle East.

Proserpinadam (Merida - Spain)
The largest reservoir impounded by the Romans was created by a dam
located near Homs, Syria in 284 AD. The dam had the extraordinary length
of 2000 m and impounded approximately 90 million m3 of water. The main
body of the dam consisted of concrete lined by masonry on both slightly
inclined faces and on the crest. It was also grossly overdesigned: in its
central part, the dam was 7 m high and 14 m wide . The crest width was
smaller, but still measured 6.6 m for the upper 1.3 m of height.


The course of the aqueduct usually followed the contour of the terrain
in order to maintain the incline while minimizing expensive construction
work

Example: Anio Novus


Roman’s method and tool to determine direction is very similar to that
still in use today

Groma Dioptra
Allowed a perfect alignment. Could trace Older than the Groma, already known to
only square angles the Greeks,could measure angles


Most of Rome's aqueducts run underground, in covered trenches or
tunnels

Advantages of underground constructions
- don't disturb surface activities such as farming or trafﬁc.
- less vulnerable to wind erosion, the weather, and
earthquakes.
- not vulnerable to enemies. Above ground arches were like
advertising to the enemy: “Here is our aqueduct. “
- labour to dig was abundant and “cheap”, construction
material and technology scarce and expensive


Trenches are used when the aqueduct follows the contours of the land.
They are quick and easy to build as they require neither the
construction of arches nor the burrowing of tunnels.

The conduit’s cover coud have different shape. Every 70
meters a big stone determined the course of the aqueduct
and marked a “no activity” strip of 1,45 meters each side.

When running near the surface, a low wall above ground
delimited a larger area of respect (4,4 meters)

It was necessary to provide a vent for the air, which
otherwise would have been compressed to such a degree
as to burst the walls or roof of the specus.


A number of carefully planned detailed ensured centuries of
functionality even after maintenance stopped

A structure way stronger than required for its
use could be caused by lack of knowledge?
“melius est abundare quam deﬁcere”


The internal lining ensured the conduit was absolutely water proof and
it can still be seen in perfect conditions 20 centuries afterwards

Hydraulic cement was called “opus signinum” or
“cocciopesto”, because it was made by crushed pottery
and even glass

It was “crushed” a second time while being laid down, to
ensure perfect adherence and smooth surface.

The lining went up to 150/170 cm. The brownish deposits
conﬁrm water level never exceeded 50/90 cm

Aqua Marcia in Vicovaro, near Rome


Opus Signinum
Opus signinum, ( cocciopesto) is a cement finishing made of lime mixed to china fragments
(terracotta) and even glass, utilized in the roman times as watertight lining for pools, water
reservoirs or in house floors.
The term comes from the city of Segni (Signa), near Rome where was allegedly invented.
Vitruvius describes the way it was made:

In the first place, procure the cleanest and sharpest sand, break up
lava into bits of not more than a pound in weight, and mix the
sand in a mortar trough with the strongest lime in the
proportion of five parts of sand to two of lime. The trench for
the signinum work, down to the level of the proposed depth of
the cistern, should be beaten with wooden beetles covered with
iron.
Then after having beaten the walls, let all the earth between them
be cleared out to a level with the very bottom of the walls.
Having evened this off, let the ground be beaten to the proper
density. If such constructions are in two compartments or in
three so as to insure clearing by changing from one to another,
they will make the water much more wholesome and sweeter to
use. For it will become more limpid, and keep its taste without
any smell, if the mud has somewhere to settle; otherwise it will
be necessary to clear it by adding salt.


Tunnels were dug in both directions from vertical shafts aligned with
the intended path of the aqueduct. This way, many teams could work
at the same time, shortening time needed to completion

Key Facts
The course was divided in sections, each of 15.000 roman feet(4.400 meters)each managed by separate teams.
Each linear meter of the aqueduct required excavating 3-4 cubic meter of soil, the construction of 1,5 cubic meters of brick
structures and 2,2 square meters of surface ﬁnishing.


Determining and maintaining the right direction was crucial, even more
so when digging tunnels

Heron described methods how to produce tunnels with his
Dioptra. So the ancient Greeks must have a sufficient
advanced geometric knowledge and the corresponding
measuring devices to produce the Eupalinos channel.

Example by Heron how to use the Dioptra to construct a tunnel
through two opposite points in a mountain. Take a point close to
the first entrance B and another point E. Then use the Dioptra to
obtain the perpendicular line EF and through a set of other
perpendicular segments get line segment KL the point M for
which DM is perpendicular to KL, where D is the other opposite
entrance point. Using DN and NB estimate the angle alpha
necessary to connect points B and D.


Determining and maintaining the right direction was crucial, even more
so when digging tunnels

The Groma was used by the Agrimensori for
Using a Groma to measure non accessible
measuring and dividing the territories in
points (example the width of a river before
“centuries” (centuratio)
crossing it


Horizontal Alignment - How to make ends meet...

Shafts (spiramen) , one every 35 or 70 meters along the Special gromas, connected to pointers down the tunnel,
intended path greatly reduce the margin of error allowed the digging team a reference direction


Horizontal Alignment - How to make ends meet...

In digging tunnels, external light, when available, could be used to ensure
alignment. By deliberatly narrowing the beam of light ,it would act as a pointer
that the workers needed to maintain at the center of the digging front


...and correct mistakes

Team 1 B

Team 2 A

Team 1

Correcting Mistakes
in case the two tunnels do not meet head to head both
teams turn in the same direction. This will certainly make
the two intersect either in point A (if team 1 has team 2 to its Evidence of course correction
left) or point B (if team 1 has team 2 to its right)

Warning!! This works only if the two tunnels
are at the same elevation (that is, are on the
same plane.


Elevation was maintained through “coltellatio”

Use of the Dioptra (at B) and two leveling
rods for determining the height of A bove B

Sighting over a mountain to determine the line of an
aqueduct channel through the base of a mountain


T ensure horizontal alignment and build the needed gradient Romans
o
used mainly the Chorobates


Short steep sections were introduced to connect aqueduct sections
built by different gangs, as a remedy for misalignment....and correct
mistakes


Archeological Analysis gives evidence of construction
methods

Left or Right handed
Excavating tunnels workers
needed the light supplied bu oil
lamps. The niches in the rock
Work Shifts Sense of Excavation where these lamps stayed are
ridges like these mark the progress of Pickaxe marks on the rock tells us the still visible. Considering the
each shift team. Progress is more in soft sense in which the tunnel has been dug sense of excavation, if the niche
rock and slowed down when passing is on le left, the worker was right
through hard rock handed, if on the right, he was
left handed


Sometimes the building shafts tunnels also acted as inspection
manholes after the construction work was done.

Manhole with a broad base Manhole on an arcaded Manhole on a siphon basin
Manhole with a small base
and settling basin aqueduct

Their main purpose was for cleaning and repairs and/or to air the water.


Settling basins (Piscina Limaria) were built to get rid of all kinds of
pollution and were mostly situated near the source of an aqueduct
and / or near the end, just before the terminal castellum divisorium, the
water distribution centre of a town or villa

Some basins had a special outlet to discharge the dirt, in other cases
the debris had to be removed periodically by hand. The best known
examples were at the aqueduct of Cologne, also an inﬁltration gallery,
(Grune Putz, Germany) and Rome (Aqua Virgo tanks)


Some settling basins were quite complex in
construction

Settling Basin Aqua Virgo in Roma


Most Aqueducts came from the Appennines East of
Rome. Many were build next to each other

Building acueducts next to each
other:

- Saved time in measuring
- save space and avoided having to
buy/conﬁscate new space
- Reduced the need for construction
(e.g. used the same service road)
- allowed to switch water from one
another during maintenance, thus
avpoiding a reduction of supply


During Maintenance water was diverted from one
aqueduct to another

In order to switch water from one aqueduct to another, they needed to cross each other in elevation.
An aqueduct could be at one point above and one point underneath another following the same
route. There were no pumps, so again water moved only by gravity. Of cource each tract was a
decline (since water cannot move uphill)This was accomplished by varying the gradient.


Most important example is the last tract of the Aqua
Marcia, Tepula, Iulia

Porta Maggiore Porta Tiburtina


Libramentum or censura declivitatis: the right gradient
was key to proper water transportation

Water flows along gradients, and its velocity depends on a
number of factors. Water flows more quickly along steeper
gradients, but wear and tear on such pipes is greater,
The right incline according to some authors
resulting in the need for more frequent repair. More gradual
sloping pipes result in slower-flowing water with greater
sludge deposits; hence, these pipes require more cleaning
with less repair.

Water velocity along conduits is also greater in larger,
smoother pipes. Pipes or canals that have rough surfaces
disrupt water flow, slowing it down. In addition, larger
diameter passageways provide less resistance, because a
smaller percentage of the flowing water is retarded by the
surface friction of the conduit. Thus, smaller diameter pipes
slow the flow of water compared to larger diameter pipes.


The average incline varied

Average Gradient (m/Km) The Nimes
Appia
aqueduct in the
0,61
Anio Vetus Pont du Gard

re
3,64
section has a
e
Marcia

d
2,83
gradient of only

ve
Tepula
34 cm per Km
i
5,07
Julia

a R
Virgo
12,51 (1:3000),
dropping only 17

D
0,19
Alsientina meters in its 50
5,85
Claudia km lenght
3,68
Anio Novus Some “steep
3,79
Traiana chutes” have an
2,63
Alexandrina incline of up to
23,50
78%


...but within the same aqueduct “ﬂat” sections were
often broken by “steep chutes”

Besides being a method of correcting
elevation mistakes, steep chutes
acted as

-energy dissipators

- aereators of the water

- sedimentation basins

Smooth chutes and stepped chutes were used for shorter
portions. Dropshaft cascade for longer ones


Some “steep chutes”

DH=drop in Height

L= Lenght of the chute

So= Slope (angle of incline)

Q/Max = Max water ﬂow in M3/sec


The Great crossing of “T Fiscale”
or

More of this later...


T 'bridge' a gap in the terrain and to prevent a long
o
detour, especially to cross a valley or a river, a bridge
for the aqueduct conduit was built.

The arched arcades require less material than walls and don't
interfere with the passage of water or people through the environment.


Bridges used one, two or three tiers of arches

The highest bridge almost 50 meters above the river Gardon is the Segovia Aqueduct
famous Pont du Gard, part of the aqueduct op Nîmes (France),


The Arch: terminology and technology

The arch stands due to compression and
attrition


The Arch: Construction

Wooden forms are used to keep pieces in place until the keystone was
placed. At that time the arch is complete and able resist high pressures


Where a valley to be crossed was too deep or too big
for a bridge, a siphon was built

Where a valley to be crossed was too deep or too big for a bridge, a siphon was
built. The aqueduct water ran into a distribution tank, often called header basin. A
The basis of a syphon is the principle of
conduit left the other side of the tank and descended into the valley, crossed the
communicating vessels
bottom on a so called 'venter' bridge and climbed up to the other side to the
'receiving' basin from which the water continued in a masonry channel to its
destination.


Communicating Vessels
When water is poured into a U-shaped water-hose, the
water reaches the same height on both sides.


Components of an inverted Siphon

HT = Header T ank
H = Height
VB = Venter Bridge
HG = Hydraulic Gradient
RT = Receiving T ank
G = Geniculus (bend)


Remains of siphons in Lyon

Headertank and ramp of the The receiving tank and ramp of
Yzeron siphon in the Gier the siphon of the Brévenne
aqueduct of Lyon (France) aqueduct of Lyon (France)


The Greeks often used cut-stone or terracotta pipes. The same applies
for the Romans in Spain, while in France they used lead pipes.

In France in particular the Romans used lead pipes. These pipes
had a small diameter which were easier to produce than the
bigger ones: commonly a series of pipes were applied in siphons
with lead pipes. The most striking example is the 8 - 10 pipes
parallel in the nine (!) siphons in the four aqueducts of Lyon
(France).

Section of the Cadiz Roman aqueduct,
rebuilt along the highway IV between
Puerto Real and San Fernando


The technology for making (lead) pipes did not make
them strong enough to withstand high pressures

Pipes were also very prone to clogging because of mineral
sediments. This is why syphons using pipes were more used in
France than in Rome, where water is very rich in calcium


Some aqueducts with Inverted Syphons


Distribution basins in the city: from
gravity to pressurized system
Closed system (Pressurized) Open system (Gravity)

Public Fountains Spas Homes,
Homes, labs
(Munera) (Termae) labs

Ground Secondary Main
Level Castellum Castellum
Underground pipes

Water outlet in the city took the form of a “castellum” (castle), a structure of viable size that
contained one or more pools, similar to the “piscina limaria”, where the ﬂow slowed down and the last
impurities could sediment. Water exited through pipes (ﬁstulae) or cup shaped outlets. These
buildings were protected by armed guards, to prevent tampering and pollution of the water


Water was never tapped directly from the aqueduct
but from special structures: the Castellum

Secondary Castellum

Users

Hydraulic
gradient

Public Fountain From
Previous
A: Main Conduct Castellum

B: Settling Tank
C: Secondary Conduct
T next
o
D: Outlet Castellum


Castellum Nimes Aqueduct


Castellum in Pompeii


Domestic water in Pompeii


Lead Pipes were called Fistulae
Lead pipes in the Roman baths in Bath (UK)

Pipes and faucets in Roman Sicily


Lead Pipes And Health
From the Antiquity it is known the harmful character of lead that could cause evident pathologies –
probably in some emperor- and intoxications along the Roman history and that caused illnesses to
the miners and lead workers and to everyone that used frequently lead –through lead fistulae and
kitchen recipients-.

However, lead becomes especially damaging in the open air, so the lead fistulae, if they were correctly
buried, must not have been as harmful as people thought.

Since almost all of the lead absorbed by the human body is deposited in bones, investigators have
studied the bones of ancient Romans. While some studies did indicate above normal concentrations
of lead, it seems unlikely that water pipes were a contributing factor. Hodge (1981) has correctly
pointed out that lead pipes would not have caused contamination for two reasons: (1) because the
Roman water contained high concentrations of calcium which formed deposits inside the pipes,
insulating the lead and (2) because lead will never greatly affect running water.

It has even been hypothesized that Rome's dependence on lead water pipes lead to its decline. It has
been suggested that the aristocracy died off from nothing more complicated than simple lead
poisoning but these hypotheses have been falsified


Many Castella served the City of Rome

Highlighted in yellow a castellum delivering
water from Aqua Iulia or Tepula, near the
Diocletianum Termae, Map of Ancient Rome by
E.Du Perac, 1574


Stones and inscriptions on the pipes still
show the name of the users

Incription referring to the Pisoni family in
Inscription referring to Marcus Aurelius
a fistula aquaria found in the submerged
city of Baia (Naples)

T manufacture these fistulae required qualified staff, so the manufacturer engraved his name on the
o
fistulae together with the owner’s name –if it was a particular-, the emperor’s name or the name of a
community; sometimes it was engraved the name of the project manager or the name of the monument. In a
fistula from Pompeii in the age of the emperor Hadrian (CIL 15, 7309) we can read: Imp[eratoris] Caes[aris]
Trai[ani] Hadriani Aug[usti] sub cura Petroni Surae proc[uratoris] Martialis ser[vus] fecit (translation
“(Property of) the emperor Caesar Trajan Hadrian Augustus, under the responsibility of Petronius Sura, the
slave Martial did it”).


How lead pipes were built

These lead fistulae were made in plates between 5 and 15 millimetres thick and 2,90 metres long; the
plates were curved with hot bronze mandrels by hammering and with clay flanges; then, both sides were
welded by running liquid lead over the clay flanges; finally, the tubes were connected with short muffs
welded in both extremes, so the workers obtained a perfect hermeticism with scarce risks of breaking
down in a normal use. The normal calibre of the pipes was established according to the water flow.

The calibre was measured in quadrants, i. e., a quarter of a inch (0,4625 centimetres); the normal
measures varied between pipes of 5 quadrants –called in Latin quinaria (2,3125 centimetres)- until pipes of 15
quadrants (6,9375 centimetres) to a smaller distribution of water, or pipes with bigger calibre to a distribution
of water in a bigger scale, the vicenaria -20 quadrants (9,35 centimetres)- and the centenaria -100 quadrants
(46,25 centimetres). The utilization of standard pipes (certified by a stamp) mandatory to help reduce frauds.


Clay Pipes were also used


Cost of Building aqueducts
For each metre of aqueduct:
- approximately 3–4 m³ of earth had to be dug up
- 1.5 m³ of concrete and bricklaying
- 2.2 m² of plaster sealant.

1 - 3 Million Sesterces per KM on Average

Avg capacity 0,5 M3/sec

Aqua Marcia: Total cost 180,000,000 sesterces
for 91 Km (£1,800,000 sterling), equivalent to
approximately 2 million Sesterces per KM

Aqua Claudia and Anio Novus, inaugurated
toghether, had a total cost of 350,000,000
(for 68 Km Claudia + 87 km Anio) (Plinius)
equivalent to 2,3 million per KM


Example: The Eifel Aqueduct

For the Eifel aqueduct, each were 15,000 Roman feet long (4,400 m or 2.7 miles in modern units). I

The complete labour expense is estimated at 475,000 man-days: with about 180 possible
construction days in the year due to weather conditions, 2,500 workers would have worked 16
months to complete the project. The actual construction time appears to have been even longer,
since this estimate leaves out the question of surveying and production of the building materials.


Inscriptions suggest control (or attempt
to control) water distribution

CIL 6.31566
Description of the distribution of
Stone mapping the villae served by Alsietina water by allotment of
aqueduct derivation time

CIL 14.3676
Regulations for use of (aqueduct)
water in the area of Tibur, setting
sizes of channels and lenth of time
for acces


Inscriptions suggest control (or attempt
to control) water distribution

Part of a decree that records the arrangements for time dependant irrigation


Payments and Frauds
The flow of water was continuous, so users paid a fixed amount according to the size of the pipe serving
their house and not for the water actually used.

T avoid frauds in the last part of the distribution system, Frontinus mandated the insertion of a brass pipe
o
(a 25 cm segment) at the beginning of each derivation pipe (fistula). Unlike lead, brass cannot be stretched,
to enlarge the section, which is the main factor in determining the amount of water to reach the user.

Correctly inserted, the calix was set half-way up the wall of the castellum, perpendicular and horizontal to it.
But, if it were placed lower in the tank or angled downward (whether deliberately or accidentally), there
would be more pressure and more water, just as there would be if the calix were directed into the flow
(XXXVI.2, CXIII.1-2). A larger calix could be placed in the tank or a larger pipe fixed to it. Or pipes could be
placed at different levels below the surface of the water. Some were not even fitted to calices or, if a new
pipe was installed, the old one was left in place to draw water, which then was sold. The result was that, of
the 14,018 quinariae officially delivered by the nine aqueducts of Rome then in use, another 10,000 quinariae
were diverted illegally (LXIV.2, LXXIV.4).


Frontinus identified and tackled the problem of
illegal connections
Frontinus for the first time made “serious”checks of the aqueducts to identify illegal taps and frauds,
which he blamed on “foreigners”, not roman citizens (cives romani). He did this by calculating the amount
of water entering the aqueduct with that coming out at the distribution basin.

. . . a large number of landed proprietors, past whose fields the aqueducts run,
tap the conduits; whence it comes that the public water courses are actually
brought to a standstill by private citizens, just to water their gardens.

Water was supposedly only piped into the abodes of those lucky enough to have official authorization, but
having running water was so desirable that Romans were constantly bribing water officials to tap an
aqueduct. Frontinus described a problem called "puncturing":

. . . There are extensive areas in various places where secret pipes run under the pavement all over the city. I
discovered that these pipes were furnishing water by special branches to all those engaged in business in
those localities through which the pipes ran, being bored for the purpose here and there by the so-called
"punctures". How large an amount of water has been stolen in his manner, I estimate by means of the fact
that a considerable quantity of lead has been brought in by the removal of that kind of branch pipe.


Maintenance of Aqueducts
After construction, the building trenches were filled in, the surface flattened, and a maintenance path built. The
maintenance path also served to delimit areas where farming was not permissible. The aqueduct to Lyon,
France was marked with the following inscription[cite this quote]:

“By command of Emperor Trajanus Hadrianus Augustus, no one is permitted to
plough, sow, or plant within the space determined for protection of the aqueduct.”

Besides repairing leaks maintenance implied cleaning the conducts from deposits. The calcium deposits brought
up ad dumped on the ground near the inspection shafts allowed archaeologists in modern times to find the long
forgotten path of the aqueducts in the (then little built) roman countryside

A very high percentage of maintenance workers, public slaves, managed to become free citizen by buying their
freedom. Contrary to other “less fortunate” slaves, they had the chance to receive bribes from the landowners
whose properties were crossed by the aqueducts, not to report (and sometimes even to build) illegal taps.


Maintenance of the aqueducts
Such a complex system needed continuous maintenance. In the time of Nerva and Trajan, a body of 460
slaves were constantly employed under the orders of the curatores aquarum in attending to the
aqueducts. This is close to the current ratio in terms of man per volum of water served (Ritrovare o
calcolare ratio) They were divided into two families, the familia publica, established by Agrippa, and the
familia Caesaris, added by Claudius; and they were subdivided into the following classes:

The villici:
attended to the pipes and calices.
The castellarii:
supervised all the castella, both within and without the city.
The circuitores:
had to go from post to post, to examine into the state of the works, and to keep watch over the laborers..
The silicarii:
had to remove and relay the pavement when the pipes beneath it required attention.
The tectores:
had charge of the masonry of the aqueducts.

With the fall of the roman Empire aqueducts began degrading not much for the arrival of the so called
“barbarians”, but for lack of maintenance and, in the absence of state control, the proliferation of private
taps along their course.


Example of Problems: Leakages

This is a close up of mineral deposits from Mineral deposits indicate leakage. View of the
the Neronian arches on the Caelian hill. interior of the arches of Aquae Felice show signs of
leakage of water from the modern day aqueduct.


At times arches needed to be reinforced

The two arches on the left are both remains of repair made
to Aqua Claudia. The original stone structure is all but
gone. These are both excellent examples of the amount of
materials used for each arch. These two arches are only
partial repairs, compared to others that were made.


Water Quality

Romans preferred drinking water with a high mineral content, preferring its taste to that of soft water.
Roman architect Vitruvius described the process for testing a source of drinking water:
“
Springs should be tested and proved in advance in the following ways. If they run free and open, inspect
and observe the physique of the people who dwell in the vicinity before beginning to conduct the
water, and if their frames are strong, their complexions fresh, legs sound, and eyes clear, the springs
deserve complete approval. If it is a spring just dug out, its water is excellent if it can be sprinkled into a
Corinthian vase or into any other sort made of good bronze without leaving a spot on it. Again, if such
water is boiled in a bronze cauldron, afterwards left for a time, and then poured off without sand or
mud being found at the bottom of the cauldron, that water also will have proved its excellence. (De
architectura, 8,4,1, trans. Morris Hickey Morgan, 1914)
”
Vitruvius insisted (8,3,28), "Consequently we must take great care and pains in searching for springs and
selecting them, keeping in view the health of mankind."


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