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

tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for the two portals common at each end, though there may be access and ve ...

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, are public utility buildings containing pumps and equipment for pumping fluids from one place to another. They are critical in a variety of infrastructure systems, such as water supply, Land reclamation, ...

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 district Drainage districts occur in England and Wales, varying in size from a few hundred acres to over , all in low-lying areas of the country where flood risk management and land drainage are sensitive issues. Most drainage districts are administered by ...

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 () was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity (), that comprised a loose collection of culturally and linguistically r ...

, the waters of

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

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

Agrigentum Agrigento (; or ) is a city on the southern coast of Sicily, Italy and capital of the province of Agrigento. Founded around 582 BC by Greek colonists from Gela, Agrigento, then known as Akragas, was one of the leading cities during the golde ...

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

ancient Romans The Roman people was the ethnicity and the body of Roman citizenship, Roman citizens (; ) during the Roman Kingdom, the Roman Republic, and the Roman Empire. This concept underwent considerable changes throughout the long history of the Roman ...

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

Trasimeno Lake Trasimeno ( , also ; ; ; ), also referred to as Trasimene ( ), Trasimeno Lake, or Thrasimene in English, is a lake in the province of Perugia, in the Umbria region of Italy on the border with Tuscany. The lake has a surface area of , m ...

, 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 Lati ...

were all drained by means of emissaries. The case of

Lake Fucino The Fucine Lake ( or ) was a large endorheic karst lake between above sea level and surrounded by the Monte Sirente-Monte Velino mountain ranges to the north-northeast, Mount Salviano to the west, Vallelonga to the south, and the Valle del Giove ...

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 or 13 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 Caesar's civil wa ...

is said to have first conceived the idea of this stupendous undertaking
(Suet. Jul. 44)

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

inaugurated what was to have been a complete drainage scheme, the

Tunnels of Claudius The Tunnels of Claudius () consist principally of a 6 km-long tunnel (or ''emissary'') together with several monumental service tunnels which Ancient Rome, Roman Emperor Claudius had built by 52 AD to partially drain the Fucine Lake in Abruzzo, p ...

br>(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 abridgement 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 Túnel Emisor Oriente, Eastern Discharge Tunnel, Eastern Wastewater Tunnel, and East Issuing Tunnel, is a wastewater treatment tunnel in Mexico City, Mexico Mexico, officially the United Mexica ...

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 ha ...

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
Flood control Roman aqueducts Ancient Roman architectural elements Hydraulic engineering {{Architecturalelement-stub

Etymology

Ancient world

Modern examples

See also

External links