A drainage tunnel, called an emissary in ancient contexts, is a

tunnel A tunnel is an underground passageway, dug through surrounding soil, earth or rock, and enclosed except for the entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube cons ...

or channel created to drain water, often from a stagnant or variable-depth body of water. It typically leads to a lower stream or river, or to a location where a

pumping station Pumping stations, also called pumphouses in situations such as well drilling, drilled wells and drinking water, are facilities containing pumps and equipment for pumping fluids from one place to another. They are used for a variety of infrastru ...

can be economically run. Drainage tunnels have frequently been constructed to drain

mining district Mining district may refer to: * Mining district (North America) * Mining district (Europe) {{dab ...

s or to serve drainage districts.

Etymology

Emissary comes from Latin ''emissarium'', from ''ex'' and ''mittere'' 'to send out'.

Ancient world

The most remarkable emissaries carry off the waters of lakes surrounded by hills. In

ancient Greece Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity ( AD 600), that comprised a loose collection of cult ...

, the waters of

Lake Copais Lake Copais, also spelled Kopais or Kopaida ( grc, Κωπαΐς; ell, Κωπαΐδα), was a lake in the centre of Boeotia, Greece, west of Thebes. It was drained in the late 19th century. It is now flat dry land and is still known as Kopaida. ...

were drained into the Cephisus; they were partly natural and partly artificial. In 480 BC, Phaeax built drains at

Agrigentum Agrigento (; scn, Girgenti or ; grc, Ἀκράγας, translit=Akrágas; la, Agrigentum or ; ar, كركنت, Kirkant, or ''Jirjant'') is a city on the southern coast of Sicily, Italy and capital of the province of Agrigento. It was one of ...

in Sicily: they were admired for their sheer size, although the workmanship was crude. The

ancient Romans In modern historiography, ancient Rome refers to Roman people, Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom ...

excelled in the construction of emissaries, as in all their hydraulic works, and remains are extant showing that lakes

Trasimeno Lake Trasimeno ( , also ; it, Lago Trasimeno ; la, Trasumennus; ett, Tarśmina), also referred to as Trasimene ( ) or Thrasimene in English, is a lake in the province of Perugia, in the Umbria region of Italy on the border with Tuscany. Th ...

, Albano and

Nemi Nemi is a town and ''comune'' in the Metropolitan City of Rome (central Italy), in the Alban Hills overlooking Lake Nemi, a volcanic crater lake. It is northwest of Velletri and about southeast of Rome. The town's name derives from the Lat ...

were all drained by means of emissaries. The case of

Lake Fucino The Fucine Lake ( it, Lago Fucino or ) was a large endorheic lake in western Abruzzo, central Italy, stretching from Avezzano in the northwest to Ortucchio in the southeast, and touching Trasacco in the southwest. Once the third largest lake in I ...

is remarkable in two ways: the attempt to drain it was one of the rare failures of Roman engineering, and the emissary is now completely above ground and open to inspection.

Julius Caesar Gaius Julius Caesar (; ; 12 July 100 BC – 15 March 44 BC), was a Roman general and statesman. A member of the First Triumvirate, Caesar led the Roman armies in the Gallic Wars before defeating his political rival Pompey in a civil war, and ...

is said to have first conceived the idea of this stupendous undertaking
(Suet. Jul. 44)
with the tunnels that bring his name,

Claudius Tiberius Claudius Caesar Augustus Germanicus (; 1 August 10 BC – 13 October AD 54) was the fourth Roman emperor, ruling from AD 41 to 54. A member of the Julio-Claudian dynasty, Claudius was born to Nero Claudius Drusus, Drusu ...

inaugurated what was to have been a complete drainage schem
(Tac. Ann. xii.57)
but the water level dropped by just 4 meters and stabilized, leaving the lake very much there. Hadrian tried it again, but failed; and it was not until 1878 that Lake Fucino was finally drained. ''The initial text of this section was an abridgment from Smith's Dictionary of Greek and Roman Antiquities (1875 edition, public domain).''

Modern examples

Modern examples of drainage tunnels include the

Emisor Oriente Tunnel The Emisor Oriente Tunnel, also known as the Tunel Emisor Oriente, Eastern Discharge Tunnel, Eastern Wastewater Tunnel, and East Issuing Tunnel, is a wastewater treatment tunnel in Mexico City, Mexico. At , it is the eighth longest tunnel in th ...

near Mexico City as well as the

Tunnel and Reservoir Plan The Tunnel and Reservoir Plan (abbreviated TARP and more commonly known as the Deep Tunnel Project or the Chicago Deep Tunnel) is a large civil engineering project that aims to reduce flooding in the metropolitan Chicago area, and to reduce the harm ...

in Chicago.

External links

Emissarium
the full article in Smith's Dictionary * Walter Dragoni, Costanza Cambi, Field Trip Guidebook for "Hydraulic Structures in Ancient Rome", field trip of the ''42nd Congress of the International Association of Hydrogeologists'', Rome, September 2015
full text

Etymology

Ancient world

Modern examples

External links

See also