Leat

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The Devonport leat near Nun's cross farm Devonport leat 6.jpg
The Devonport leat near Nun's cross farm

A leat (also lete or leet, or millstream) is the name, common in the south and west of England and in Wales (Lade in Scotland), for an artificial watercourse or aqueduct dug into the ground, especially one supplying water to a watermill or its mill pond. Other common uses for leats include delivery of water for mineral washing and concentration, for irrigation, 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.

Wales Country in northwest Europe, part of the United Kingdom

Wales is a country that is part of the United Kingdom and the island of Great Britain. It is bordered by England to the east, the Irish Sea to the north and west, and the Bristol Channel to the south. It had a population in 2011 of 3,063,456 and has a total area of 20,779 km2 (8,023 sq mi). Wales has over 1,680 miles (2,700 km) of coastline and is largely mountainous, with its higher peaks in the north and central areas, including Snowdon, its highest summit. The country lies within the north temperate zone and has a changeable, maritime climate.

Scotland Country in Europe, part of the United Kingdom

Scotland is a country that is part of the United Kingdom. Sharing a border with England to the southeast, Scotland is otherwise surrounded by the Atlantic Ocean to the north and west, by the North Sea to the northeast and by the Irish Sea to the south. In addition to the mainland, situated on the northern third of the island of Great Britain, Scotland has over 790 islands, including the Northern Isles and the Hebrides.

Watercourse channel that a flowing body of water follows

A watercourse is the channel that a flowing body of water follows. In the UK, some aspects of criminal law, such as The Rivers Act 1951, specify that a watercourse includes those rivers which are dry for part of the year.

Contents

According to the Oxford English Dictionary , leat is cognate 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, 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.

<i>Oxford English Dictionary</i> Premier historical dictionary of the English language

The Oxford English Dictionary (OED) is the principal historical dictionary of the English language, published by Oxford University Press. It traces the historical development of the English language, providing a comprehensive resource to scholars and academic researchers, as well as describing usage in its many variations throughout the world. The second edition, comprising 21,728 pages in 20 volumes, was published in 1989.

Cognate word that has a common etymological origin

In linguistics, cognates are words that have a common etymological origin. Cognates are often inherited from a shared parent language, but they may also involve borrowings from some other language. For example, the English words dish and desk and the German word Tisch ("table") are cognates because they all come from Latin discus, which relates to their flat surfaces. Cognates may have evolved similar, different or even opposite meanings, but in most cases there are some similar sounds or letters in the words, in some cases appearing to be dissimilar. Some words sound similar, but don't come from the same root; these are called false cognates.

Sheffield City and Metropolitan borough in England

Sheffield is a city and metropolitan borough in South Yorkshire, England. Historically part of the West Riding of Yorkshire, its name derives from the River Sheaf, which runs through the city. With some of its southern suburbs annexed from Derbyshire, the city has grown from its largely industrial roots to encompass a wider economic base. The population of the City of Sheffield is 577,800 (mid-2017 est.) and it is one of the eight largest regional English cities that make up the Core Cities Group. Sheffield is the third-largest English district by population. The metropolitan population of Sheffield is 1,569,000.

Design and functions

Leats generally start some distance (a few hundred yards, or perhaps several miles) above the mill or other destination, where an offtake or sluice gate diverts a proportion of the water from a river or stream. A weir 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 determines the flow rate together with the quality of the wetted surface of the leat. The flow rate may be calculated using the Manning formula. By the time it arrives at the water mill the difference in levels between the leat and the main stream is great enough to provide a useful head 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.

Sluice A water channel controlled at its head by a gate

A sluice is a water channel controlled at its head by a gate. A mill race, leet, flume, penstock or lade is a sluice channelling water toward a water mill. The terms sluice, sluice gate, knife gate, and slide gate are used interchangeably in the water and wastewater control industry.

River Natural flowing watercourse

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 water. Small rivers can be referred to using names such as stream, creek, brook, rivulet, and rill. There are no official definitions for the generic term river as applied to geographic features, although in some countries or communities a stream is defined by its size. Many names for small rivers are specific to geographic location; examples are "run" in some parts of the United States, "burn" in Scotland and northeast England, and "beck" in northern England. Sometimes a river is defined as being larger than a creek, but not always: the language is vague.

Stream A body of surface water flowing down a channel

A stream is a body of water with surface water flowing within the bed and banks of a channel. The stream encompasses surface and groundwater fluxes that respond to geological, geomorphological, hydrological and biotic controls.

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

Map of the Roman gold mine Dolaucothimap2.jpg
Map of the Roman gold mine
The aqueducts at Dolaucothi Aqueduct1.jpg
The aqueducts at Dolaucothi

Leats were built to work lead, tin and silver ores in mining areas of Wales, Cornwall, Devon, the Pennines and the Leadhills/Wanlockhead area of Southern Scotland from the 17th century onwards. They were used to supply water for hushing mineral deposits, washing ore and powering mills.

Lead Chemical element with atomic number 82

Lead is a chemical element with symbol Pb 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 cut, lead is silvery with a hint of blue; it tarnishes to a dull gray color when exposed to air. Lead has the highest atomic number of any stable element and three of its isotopes are endpoints of major nuclear decay chains of heavier elements.

Tin Chemical element with atomic number 50

Tin is a chemical element with the symbol Sn (from Latin: stannum) and atomic number 50. It is a post-transition metal in group 14 of the periodic table of elements. It is obtained chiefly from the mineral cassiterite, which contains stannic oxide, SnO2. Tin shows a chemical similarity to both of its neighbors in group 14, germanium and lead, and has two main oxidation states, +2 and the slightly more stable +4. Tin is the 49th most abundant element and has, with 10 stable isotopes, the largest number of stable isotopes in the periodic table, thanks to its magic number of protons. It has two main allotropes: at room temperature, the stable allotrope is β-tin, a silvery-white, malleable metal, but at low temperatures it transforms into the less dense grey α-tin, which has the diamond cubic structure. Metallic tin does not easily oxidize in air.

Silver Chemical element with atomic number 47

Silver is a chemical element with symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal is found in the Earth's crust in the pure, free elemental form, as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold, lead, and zinc refining.


Use in Roman times

Leats were also used extensively by the Romans, and can still be seen at many sites, such as the Dolaucothi goldmines. They used the aqueducts to prospect for ores by sluicing away the overburden of soil to reveal the bedrock in a method known as hushing. They could then attack the ore veins by fire-setting, quench with water from a tank above the workings, and remove the debris with waves of water, a method still used in hydraulic mining. The water supply could then be used for washing the ore after crushing by simple machines also driven by water.

Ancient Rome History of Rome from the 8th-century BC to the 5th-century

In historiography, ancient Rome is Roman civilization from the founding of the Italian city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD, encompassing the Roman Kingdom, Roman Republic and Roman Empire until the fall of the western empire. The civilization began as an Italic settlement in the Italian Peninsula, conventionally founded in 753 BC, that grew into the city of Rome and which subsequently gave its name to the empire over which it ruled and to the widespread civilisation the empire developed. The Roman Empire expanded to become one of the largest empires in the ancient world, though still ruled from the city, with an estimated 50 to 90 million inhabitants and covering 5.0 million square kilometres at its height in AD 117.

Dolaucothi Gold Mines gold mine

The Dolaucothi Gold Mines, 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 mines are located within the Dolaucothi Estate which is now owned by the National Trust.

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 soil and sub-soil, which must be stripped away to discover the ore veins. A flood of water is very effective in moving soil as well as working the ore deposits when combined with other methods such as fire-setting.

The Romans also used them for supplying water to the bath-houses or thermae and to drive vertical water-wheels.

<i>Thermae</i> public facilities for bathing in ancient Rome

In ancient Rome, thermae and balneae were facilities for bathing. Thermae usually refers to the large imperial bath complexes, while balneae were smaller-scale facilities, public or private, that existed in great numbers throughout Rome.

Dartmoor

Devonport leat showing sluice gates Devonport leat 3.jpg
Devonport leat showing sluice gates

See also

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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.

Watermill structure that uses a water wheel or turbine to drive a mechanical process

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 many material goods, including flour, lumber, paper, textiles, and many metal products. These watermills may comprise gristmills, sawmills, paper mills, textile mills, hammermills, trip hammering mills, rolling mills, wire drawing mills.

Placer mining technique of mining stream bed deposits for minerals

Placer mining is the mining of stream bed (alluvial) deposits for minerals. This may be done by open-pit or by various surface excavating equipment or tunnelling equipment.

Dartmoor tin-mining

The tin mining industry on Dartmoor, Devon, England, is thought to have originated in pre-Roman times, and continued right through to the 20th century, when the last commercially worked mine closed in November 1930. From the 12th century onwards tin mining was regulated by a Stannary Parliament which had its own laws.

Flume human-made channel for water

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Penstock Intake structure that controls water flow to turbines or sewerage systems

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.

Pumsaint village in United Kingdom

Pumsaint is a village in Carmarthenshire, Wales situated half way between Llanwrda and Lampeter on the A482 in the valley of the Afon Cothi. It forms part of the extensive estate of Dolaucothi which is owned by the National Trust.

Loch Thom reservoir in the United Kingdom

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Roman aqueduct type of aqueduct built by the Romans

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Drakes 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 17.5 miles (28.2 km) in order to supply Plymouth with water. It began at a point now under water at Burrator Reservoir, from which its path now emerges some 10m lower than the typical reservoir water level. It was one of the first municipal water supplies in the country.

Millstream may refer to:

River Meavy river in the United Kingdom

The River Meavy is a river in the southwest part of Dartmoor in Devon in south-west England. It runs entirely in the national park and connects Burrator Reservoir to the River Plym.

The technology history of the Roman military covers the development of and application of technologies for use in the armies and navies of Rome from the Roman Republic to the fall of the Western Roman Empire. The rise of Hellenism and the Roman Republic are generally seen as signalling the end of the Iron Age in the Mediterranean. Roman iron-working was enhanced by a process known as carburization. The Romans used the better properties in their armaments, and the 1,300 years of Roman military technology saw radical changes. The Roman armies of the early empire were much better equipped than early republican armies. Metals used for arms and armor primarily included iron, bronze, and brass. For construction, the army used wood, earth, and stone. The later use of concrete in architecture was widely mirrored in Roman military technology, especially in the application of a military workforce to civilian construction projects.

Dartmoor reservoirs

Over the course of the 19th and 20th centuries, several reservoirs and dams were built in the area now covered by Dartmoor National Park in Devon, England to supply drinking water to the rapidly growing towns in the surrounding lowlands. With its deep valleys and high rainfall, Dartmoor was an inevitable location. New reservoirs continued construction even after the establishment of the National Park in 1951.

References

  1. Tim Sandles, 21 March 2016: Leats at legendarydartmoor.co.uk, accessed 5 April 2018
  2. Robins, J. (1984) Follow the leat with John Robins: a series of walks along Dartmoor leats and a description of the mines some of them served, John Robins, ISBN   0-9508030-0-6
  3. Hawkings, D.J. (1987) Water from the moor, Devon, ISBN   0-86114-788-X Provides a full history of the leats which supplied Plymouth, England.