![Devonport leat 6](https://upload.wikimedia.org/wikipedia/commons/f/f6/Devonport_leat_6.jpg)
A leat (; also lete or leet, or millstream) is the name, common in the south and west of England and in
Wales
Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...
, for an artificial
watercourse
A stream is a continuous body of surface water flowing within the bed and banks of a channel. Depending on its location or certain characteristics, a stream may be referred to by a variety of local or regional names. Long large streams are ...
or
aqueduct dug into the ground, especially one supplying water to a
watermill
A watermill or water mill is a mill that uses hydropower. It is a structure that uses a water wheel or water turbine to drive a mechanical process such as milling (grinding), rolling, or hammering. Such processes are needed in the production of ...
or its
mill pond
A mill pond (or millpond) is a body of water used as a reservoir for a water-powered mill.
Description
Mill ponds were often created through the construction of a mill dam or weir (and mill stream) across a waterway.
In many places, the com ...
. Other common uses for leats include delivery of water for
hydraulic mining
Hydraulic mining is a form of mining that uses high-pressure jets of water to dislodge rock material or move sediment.Paul W. Thrush, ''A Dictionary of Mining, Mineral, and Related Terms'', US Bureau of Mines, 1968, p.560. In the placer mining of ...
and
mineral concentration, for
irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...
, to serve a
dye works or other industrial plant, and provision of drinking water to a farm or household or as a catchment cut-off to improve the yield of a
reservoir
A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation.
Reservoirs can be created in a number of ways, including contro ...
.
According to the ''
Oxford English Dictionary
The ''Oxford English Dictionary'' (''OED'') is the first and foundational historical dictionary of the English language, published by Oxford University Press (OUP). It traces the historical development of the English language, providing a com ...
'', ''leat'' is
cognate
In historical linguistics, cognates or lexical cognates are sets of words in different languages that have been inherited in direct descent from an etymology, etymological ancestor in a proto-language, common parent language. Because language c ...
with ''let'' in the sense of "allow to pass through". Other names for the same thing include ''fleam'' (probably a leat supplying water to a mill that did not have a millpool). In parts of northern England, for example around
Sheffield
Sheffield is a city status in the United Kingdom, city in South Yorkshire, England, whose name derives from the River Sheaf which runs through it. The city serves as the administrative centre of the City of Sheffield. It is Historic counties o ...
, the equivalent word is ''goit''. In southern England, a leat used to supply water for
water-meadow irrigation is often called a ''carrier'', ''top carrier'', or ''main''.
Design and functions
Water mills
Leats generally start some distance (a few hundred yards, or perhaps several miles) above the mill or other destination, where an
offtake or
sluice
Sluice ( ) is a word for a channel controlled at its head by a movable gate which is called a sluice gate. A sluice gate is traditionally a wood or metal barrier sliding in grooves that are set in the sides of the waterway and can be considered ...
gate diverts a proportion of the water from a
river
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...
or
stream
A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...
. A
weir
A weir or low head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the river level. Weirs are also used to control the flow of water for outlets of l ...
in the source stream often serves to provide a reservoir of water adequate for diversion. The leat then runs along the edge or side of the valley, at a shallower slope than the main stream. The gradient, together with the quality of the wetted surface of the leat, determines the
flow rate. The flow rate may be calculated using the
Manning formula The Manning formula or Manning's equation is an empirical formula estimating the average velocity of a liquid flowing in a conduit that does not completely enclose the liquid, i.e., open channel flow. However, this equation is also used for calculat ...
. By the time it arrives at the
water mill
A watermill or water mill is a mill that uses hydropower. It is a structure that uses a water wheel or water turbine to drive a mechanical process such as milling (grinding), rolling, or hammering. Such processes are needed in the production o ...
the difference in levels between the leat and the main stream is great enough to provide a useful
head
A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may ...
of water – several metres (perhaps 5 to 15 feet) for a watermill, or a metre or less (perhaps one to four feet) for the controlled irrigation of a
water-meadow.
Water supply
Leats are used to increase the yield of a reservoir by trapping streams in nearby catchments by means of a contour leat. This captures part or all of the stream flow and transports it along the contour to the reservoir. Such leats are common around reservoirs in the uplands of Wales.
Mining
![Aqueduct1](https://upload.wikimedia.org/wikipedia/commons/1/1d/Aqueduct1.jpg)
Leats were built to work
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
,
tin
Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal.
Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
and
silver
Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
ores in mining areas of
Wales
Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...
,
Cornwall
Cornwall (; kw, Kernow ) is a historic county and ceremonial county in South West England. It is recognised as one of the Celtic nations, and is the homeland of the Cornish people. Cornwall is bordered to the north and west by the Atlantic ...
,
Devon
Devon ( , historically known as Devonshire , ) is a ceremonial and non-metropolitan county in South West England. The most populous settlement in Devon is the city of Plymouth, followed by Devon's county town, the city of Exeter. Devon is ...
, the
Pennines
The Pennines (), also known as the Pennine Chain or Pennine Hills, are a range of uplands running between three regions of Northern England: North West England on the west, North East England and Yorkshire and the Humber on the east. Commo ...
and the
Leadhills
Leadhills, originally settled for the accommodation of miners, is a village in South Lanarkshire, Scotland, WSW of Elvanfoot. The population in 1901 was 835. It was originally known as Waterhead.
It is the second highest village in Scotland, ...
/
Wanlockhead
Wanlockhead is a village in Dumfries and Galloway, Scotland, nestling in the Lowther Hills and south of Leadhills at the head of the Mennock Pass, which forms part of the Southern Uplands. It is Scotland's highest village, at an elevation of ar ...
area of Southern
Scotland
Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...
from the 17th century onwards. They were used to supply water for
hushing
Hushing is an ancient and historic mining method using a flood or torrent of water to reveal mineral veins. The method was applied in several ways, both in prospecting for ores, and for their exploitation. Mineral veins are often hidden below ...
mineral deposits, washing ore and powering mills.
Use in Roman times
Leats were also used extensively by the
Romans
Roman or Romans most often refers to:
*Rome, the capital city of Italy
* Ancient Rome, Roman civilization from 8th century BC to 5th century AD
*Roman people, the people of ancient Rome
*''Epistle to the Romans'', shortened to ''Romans'', a lette ...
, and can still be seen at many sites, such as the
Dolaucothi
The Dolaucothi Gold Mines (; cy, Mwynfeydd Aur Dolaucothi) (), also known as the Ogofau Gold Mine, are ancient Roman surface and underground mines located in the valley of the River Cothi, near Pumsaint, Carmarthenshire, Wales. The gold min ...
goldmines. They used the
aqueducts
Aqueduct may refer to:
Structures
*Aqueduct (bridge), a bridge to convey water over an obstacle, such as a ravine or valley
*Navigable aqueduct, or water bridge, a structure to carry navigable waterway canals over other rivers, valleys, railw ...
to
prospect for ores by sluicing away the overburden of soil to reveal the bedrock in a method known as
hushing
Hushing is an ancient and historic mining method using a flood or torrent of water to reveal mineral veins. The method was applied in several ways, both in prospecting for ores, and for their exploitation. Mineral veins are often hidden below ...
. They could then attack the ore veins by
fire-setting
Fire-setting is a method of traditional mining used most commonly from Prehistory, prehistoric times up to the Middle Ages. Fires were set against a rock face to heat the Rock (geology), stone, which was then doused with liquid, causing the sto ...
, quench with water from a tank above the workings, and remove the debris with waves of water, a method still used in
hydraulic mining
Hydraulic mining is a form of mining that uses high-pressure jets of water to dislodge rock material or move sediment.Paul W. Thrush, ''A Dictionary of Mining, Mineral, and Related Terms'', US Bureau of Mines, 1968, p.560. In the placer mining of ...
. The water supply could then be used for washing the ore after crushing by simple machines also driven by water.
The Romans also used them for supplying water to the bath-houses or
thermae
In ancient Rome, (from Greek , "hot") and (from Greek ) were facilities for bathing. usually refers to the large Roman Empire, imperial public bath, bath complexes, while were smaller-scale facilities, public or private, that existed i ...
and to drive vertical
water-wheels.
![Devonport leat 3](https://upload.wikimedia.org/wikipedia/commons/7/74/Devonport_leat_3.jpg)
Dartmoor
There are many leats on
Dartmoor
Dartmoor is an upland area in southern Devon, England. The moorland and surrounding land has been protected by National Park status since 1951. Dartmoor National Park covers .
The granite which forms the uplands dates from the Carboniferous ...
, mostly constructed to provide power for mining activities, although some were also sources of drinking water. The courses of many Dartmoor leats may still be followed.
[Hawkings, D.J. (1987) ''Water from the moor'', Devon, Provides a full history of the leats which supplied Plymouth, England.] Many such leats on the moor are marked on the 1:50000 and 1:25000
Ordnance Survey
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, logo_caption =
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maps, such as that serving the now-defunct
Vitifer mine near the
Warren House Inn
The Warren House Inn is a remote and isolated public house in the heart of Dartmoor, Devon, England. It is the highest pub in southern England at 1,425 feet (434 m) above sea level. It is located on an ancient road across the moor, abou ...
. Notable leats include:
*
Drake's Leat
Drake's Leat, also known as Plymouth Leat, was a watercourse constructed in the late 16th century to tap the River Meavy on Dartmoor, England, from which it ran in order to supply Plymouth with water. It began at a point now under water at Burr ...
, constructed in 1591 under the management of
Sir Francis Drake
Sir Francis Drake ( – 28 January 1596) was an English explorer, sea captain, privateer, slave trader, naval officer, and politician. Drake is best known for his circumnavigation of the world in a single expedition, from 1577 to 1580 ( ...
, as an agent of the Corporation of Plymouth, to carry water from
Dartmoor
Dartmoor is an upland area in southern Devon, England. The moorland and surrounding land has been protected by National Park status since 1951. Dartmoor National Park covers .
The granite which forms the uplands dates from the Carboniferous ...
to
Plymouth
Plymouth () is a port city and unitary authority in South West England. It is located on the south coast of Devon, approximately south-west of Exeter and south-west of London. It is bordered by Cornwall to the west and south-west.
Plymouth ...
.
*
Devonport Leat
The Devonport Leat is a leat in Devon constructed in the 1790s to carry fresh drinking water from the high ground of Dartmoor to the expanding dockyards at Plymouth Dock (which was renamed as Devonport, Devon on 1 January 1824).
Feedwaters
It ...
constructed in the late 18th century to carry water to the expanding naval dockyard at
Devonport (now a part of Plymouth).
See also
*
Acequia
An acequia () or séquia () is a community-operated watercourse used in Spain and former Spanish colonies in the Americas for irrigation. Particularly in Spain, the Andes, northern Mexico, and the modern-day American Southwest particularly n ...
*
Aqueduct (watercourse)
An aqueduct is a watercourse constructed to carry water from a source to a distribution point far away. In modern engineering, the term ''aqueduct'' is used for any system of pipes, ditches, canals, tunnels, and other structures used for this p ...
*
Flume
A flume is a human-made channel for water, in the form of an open declined gravity chute whose walls are raised above the surrounding terrain, in contrast to a trench or ditch. Flumes are not to be confused with aqueducts, which are built to t ...
* ''
Kunstgraben
A ''Kunstgraben'' is a type of man-made water channel that was once used by mines to drive the water wheels needed for power, mine drainage and a host of other purposes. The term is German (plural: ''Kunstgräben''). Similar ditches supplyin ...
''
*
Mill race
A mill race, millrace or millrun, mill lade (Scotland) or mill leat (Southwest England) is the current of water that turns a water wheel, or the channel ( sluice) conducting water to or from a water wheel. Compared with the broad waters of a mi ...
*
Penstock
A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydro turbines and sewerage systems. The term is inherited from the earlier technology of mill ponds and watermills.
H ...
*
Roman aqueduct
The Romans constructed aqueducts throughout their Republic and later Empire, to bring water from outside sources into cities and towns. Aqueduct water supplied public baths, latrines, fountains, and private households; it also supported mining o ...
*
Roman engineering
The ancient Romans were famous for their advanced engineering accomplishments. Technology for bringing running water into cities was developed in the east, but transformed by the Romans into a technology inconceivable in Greece. The architecture ...
*
Roman mining
References
External links
{{Rivers, streams and springs
Aqueducts in the United Kingdom
History of mining
Hydraulic engineering
Water management in mining
cs:Náhon
nrm:Bieu