overshot water wheel efficiency made in china

A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a wheel (usually constructed from wood or metal), with a number of blades or buckets arranged on the outside rim forming the driving car. Water wheels were still in commercial use well into the 20th century but they are no longer in common use. Uses included milling flour in gristmills, grinding wood into pulp for papermaking, hammering wrought iron, machining, ore crushing and pounding fibre for use in the manufacture of cloth.

Some water wheels are fed by water from a mill pond, which is formed when a flowing stream is dammed. A channel for the water flowing to or from a water wheel is called a mill race. The race bringing water from the mill pond to the water wheel is a headrace; the one carrying water after it has left the wheel is commonly referred to as a tailrace.

Waterwheels were used for various purposes from agriculture to metallurgy in ancient civilizations spanning the Hellenistic Greek world, Rome, China and India. Waterwheels saw continued use in the Post-classical age, like the Middle Ages of Europe and the Islamic Golden Age, but also elsewhere. In the mid to late 18th century John Smeaton"s scientific investigation of the water wheel led to significant increases in efficiency supplying much needed power for the Industrial Revolution.turbine, developed by Benoît Fourneyron, beginning with his first model in 1827.elevations, that exceed the capability of practical-sized waterwheels.

The main difficulty of water wheels is their dependence on flowing water, which limits where they can be located. Modern hydroelectric dams can be viewed as the descendants of the water wheel, as they too take advantage of the movement of water downhill.

Overshot and backshot water wheels are typically used where the available height difference is more than a couple of meters. Breastshot wheels are more suited to large flows with a moderate head. Undershot and stream wheel use large flows at little or no head.

There is often an associated millpond, a reservoir for storing water and hence energy until it is needed. Larger heads store more gravitational potential energy for the same amount of water so the reservoirs for overshot and backshot wheels tend to be smaller than for breast shot wheels.

Overshot and pitchback water wheels are suitable where there is a small stream with a height difference of more than 2 metres (6.5 ft), often in association with a small reservoir. Breastshot and undershot wheels can be used on rivers or high volume flows with large reservoirs.

Stream wheels are cheaper and simpler to build and have less of an environmental impact, than other types of wheels. They do not constitute a major change of the river. Their disadvantages are their low efficiency, which means that they generate less power and can only be used where the flow rate is sufficient. A typical flat board undershot wheel uses about 20 percent of the energy in the flow of water striking the wheel as measured by English civil engineer John Smeaton in the 18th century.

Stream wheels mounted on floating platforms are often referred to as hip wheels and the mill as a ship mill. They were sometimes mounted immediately downstream from bridges where the flow restriction of the bridge piers increased the speed of the current.

An undershot wheel is a vertically mounted water wheel with a horizontal axle that is rotated by the water from a low weir striking the wheel in the bottom quarter. Most of the energy gain is from the movement of the water and comparatively little from the head. They are similar in operation and design to stream wheels.

The word breastshot is used in a variety of ways. Some authors restrict the term to wheels where the water enters at about the 10 o’clock position, others 9 o’clock, and others for a range of heights.

The small clearance between the wheel and the masonry requires that a breastshot wheel has a good trash rack ("screen" in British English) to prevent debris from jamming between the wheel and the apron and potentially causing serious damage.

Breastshot wheels are less efficient than overshot and backshot wheels but they can handle high flow rates and consequently high power. They are preferred for steady, high-volume flows such as are found on the Fall Line of the North American East Coast. Breastshot wheels are the most common type in the United States of America

A vertically mounted water wheel that is rotated by water entering buckets just past the top of the wheel is said to be overshot. The term is sometimes, erroneously, applied to backshot wheels, where the water goes down behind the wheel.

A typical overshot wheel has the water channeled to the wheel at the top and slightly beyond the axle. The water collects in the buckets on that side of the wheel, making it heavier than the other "empty" side. The weight turns the wheel, and the water flows out into the tail-water when the wheel rotates enough to invert the buckets. The overshot design is very efficient, it can achieve 90%,

Nearly all of the energy is gained from the weight of water lowered to the tailrace although a small contribution may be made by the kinetic energy of the water entering the wheel. They are suited to larger heads than the other type of wheel so they are ideally suited to hilly countries. However even the largest water wheel, the Laxey Wheel in the Isle of Man, only utilises a head of around 30 m (100 ft). The world"s largest head turbines, Bieudron Hydroelectric Power Station in Switzerland, utilise about 1,869 m (6,132 ft).

Overshot wheels require a large head compared to other types of wheel which usually means significant investment in constructing the headrace. Sometimes the final approach of the water to the wheel is along a flume or penstock, which can be lengthy.

A backshot wheel (also called pitchback) is a variety of overshot wheel where the water is introduced just before the summit of the wheel. In many situations, it has the advantage that the bottom of the wheel is moving in the same direction as the water in the tailrace which makes it more efficient. It also performs better than an overshot wheel in flood conditions when the water level may submerge the bottom of the wheel. It will continue to rotate until the water in the wheel pit rises quite high on the wheel. This makes the technique particularly suitable for streams that experience significant variations in flow and reduces the size, complexity, and hence cost of the tailrace.

The direction of rotation of a backshot wheel is the same as that of a breastshot wheel but in other respects, it is very similar to the overshot wheel. See below.

Some wheels are overshot at the top and backshot at the bottom thereby potentially combining the best features of both types. The photograph shows an example at Finch Foundry in Devon, UK. The head race is the overhead timber structure and a branch to the left supplies water to the wheel. The water exits from under the wheel back into the stream.

A special type of overshot/backshot wheel is the reversible water wheel. This has two sets of blades or buckets running in opposite directions so that it can turn in either direction depending on which side the water is directed. Reversible wheels were used in the mining industry in order to power various means of ore conveyance. By changing the direction of the wheel, barrels or baskets of ore could be lifted up or lowered down a shaft or inclined plane. There was usually a cable drum or a chain basket on the axle of the wheel. It is essential that the wheel have braking equipment to be able to stop the wheel (known as a braking wheel). The oldest known drawing of a reversible water wheel was by Georgius Agricola and dates to 1556.

The earliest waterwheel working like a lever was described by Zhuangzi in the late Warring States period (476-221 BC). It says that the waterwheel was invented by Zigong, a disciple of Confucius in the 5th century BC.Chinese of the Eastern Han Dynasty were using water wheels to crush grain in mills and to power the piston-bellows in forging iron ore into cast iron.

In the text known as the Xin Lun written by Huan Tan about 20 AD (during the usurpation of Wang Mang), it states that the legendary mythological king known as Fu Xi was the one responsible for the pestle and mortar, which evolved into the tilt-hammer and then trip hammer device (see trip hammer). Although the author speaks of the mythological Fu Xi, a passage of his writing gives hint that the water wheel was in widespread use by the 1st century AD in China (Wade-Giles spelling):

Fu Hsi invented the pestle and mortar, which is so useful, and later on it was cleverly improved in such a way that the whole weight of the body could be used for treading on the tilt-hammer (tui), thus increasing the efficiency ten times. Afterwards the power of animals—donkeys, mules, oxen, and horses—was applied by means of machinery, and water-power too used for pounding, so that the benefit was increased a hundredfold.

In the year 31 AD, the engineer and Prefect of Nanyang, Du Shi (d. 38), applied a complex use of the water wheel and machinery to power the bellows of the blast furnace to create cast iron. Du Shi is mentioned briefly in the Hou Han Shu) as follows (in Wade-Giles spelling):

In the seventh year of the Chien-Wu reign period (31 AD) Tu Shih was posted to be Prefect of Nanyang. He was a generous man and his policies were peaceful; he destroyed evil-doers and established the dignity (of his office). Good at planning, he loved the common people and wished to save their labor. He invented a water-power reciprocator (shui phai) for the casting of (iron) agricultural implements. Those who smelted and cast already had the push-bellows to blow up their charcoal fires, and now they were instructed to use the rushing of the water (chi shui) to operate it ... Thus the people got great benefit for little labor. They found the "water(-powered) bellows" convenient and adopted it widely.

Water wheels in China found practical uses such as this, as well as extraordinary use. The Chinese inventor Zhang Heng (78–139) was the first in history to apply motive power in rotating the astronomical instrument of an armillary sphere, by use of a water wheel.mechanical engineer Ma Jun (c. 200–265) from Cao Wei once used a water wheel to power and operate a large mechanical puppet theater for the Emperor Ming of Wei (r. 226–239).

The ancient Greeks invented the waterwheel independently and used it in nearly all of the forms and functions described above, including its application for watermilling.Hellenistic period between the 3rd and 1st century BC.

The compartmented water wheel comes in two basic forms, the wheel with compartmented body (Latin tympanum) and the wheel with compartmented rim or a rim with separate, attached containers.sakia gear.

The earliest literary reference to a water-driven, compartmented wheel appears in the technical treatise Pneumatica (chap. 61) of the Greek engineer Philo of Byzantium (ca. 280−220 BC).Parasceuastica (91.43−44), Philo advises the use of such wheels for submerging siege mines as a defensive measure against enemy sapping.dry docks in Alexandria under the reign of Ptolemy IV (221−205 BC).papyri of the 3rd to 2nd century BC mention the use of these wheels, but don"t give further details.Ancient Near East before Alexander"s conquest can be deduced from its pronounced absence from the otherwise rich oriental iconography on irrigation practices.

The earliest depiction of a compartmented wheel is from a tomb painting in Ptolemaic Egypt which dates to the 2nd century BC. It shows a pair of yoked oxen driving the wheel via a sakia gear, which is here for the first time attested, too.Museum of Alexandria, at the time the most active Greek research center, may have been involved in its invention.Alexandrian War in 48 BC tells of how Caesar"s enemies employed geared waterwheels to pour sea water from elevated places on the position of the trapped Romans.

Around 300 AD, the noria was finally introduced when the wooden compartments were replaced with inexpensive ceramic pots that were tied to the outside of an open-framed wheel.

The Romans used waterwheels extensively in mining projects, with enormous Roman-era waterwheels found in places like modern-day Spain. They were reverse overshot water-wheels designed for dewatering deep underground mines.Vitruvius, including the reverse overshot water-wheel and the Archimedean screw. Many were found during modern mining at the copper mines at Rio Tinto in Spain, one system involving 16 such wheels stacked above one another so as to lift water about 80 feet from the mine sump. Part of such a wheel was found at Dolaucothi, a Roman gold mine in south Wales in the 1930s when the mine was briefly re-opened. It was found about 160 feet below the surface, so must have been part of a similar sequence as that discovered at Rio Tinto. It has recently been carbon dated to about 90 AD, and since the wood from which it was made is much older than the deep mine, it is likely that the deep workings were in operation perhaps 30–50 years after. It is clear from these examples of drainage wheels found in sealed underground galleries in widely separated locations that building water wheels was well within their capabilities, and such verticals water wheels commonly used for industrial purposes.

Taking indirect evidence into account from the work of the Greek technician Apollonius of Perge, the British historian of technology M.J.T. Lewis dates the appearance of the vertical-axle watermill to the early 3rd century BC, and the horizontal-axle watermill to around 240 BC, with Byzantium and Alexandria as the assigned places of invention.Strabon (ca. 64 BC–AD 24) to have existed sometime before 71 BC in the palace of the Pontian king Mithradates VI Eupator, but its exact construction cannot be gleaned from the text (XII, 3, 30 C 556).

The first clear description of a geared watermill offers the late 1st century BC Roman architect Vitruvius who tells of the sakia gearing system as being applied to a watermill.

About the same time, the overshot wheel appears for the first time in a poem by Antipater of Thessalonica, which praises it as a labour-saving device (IX, 418.4–6).Lucretius (ca. 99–55 BC) who likens the rotation of the waterwheel to the motion of the stars on the firmament (V 516).central Gaul.Barbegal watermill complex a series of sixteen overshot wheels was fed by an artificial aqueduct, a proto-industrial grain factory which has been referred to as "the greatest known concentration of mechanical power in the ancient world".

In Roman North Africa, several installations from around 300 AD were found where vertical-axle waterwheels fitted with angled blades were installed at the bottom of a water-filled, circular shaft. The water from the mill-race which entered tangentially the pit created a swirling water column that made the fully submerged wheel act like true water turbines, the earliest known to date.

Apart from its use in milling and water-raising, ancient engineers applied the paddled waterwheel for automatons and in navigation. Vitruvius (X 9.5–7) describes multi-geared paddle wheels working as a ship odometer, the earliest of its kind. The first mention of paddle wheels as a means of propulsion comes from the 4th–5th century military treatise

Ancient water-wheel technology continued unabated in the early medieval period where the appearance of new documentary genres such as legal codes, monastic charters, but also hagiography was accompanied with a sharp increase in references to watermills and wheels.

The earliest excavated water wheel driven by tidal power was the Nendrum Monastery mill in Northern Ireland which has been dated to 787, although a possible earlier mill dates to 619. Tide mills became common in estuaries with a good tidal range in both Europe and America generally using undershot wheels.

Cistercian monasteries, in particular, made extensive use of water wheels to power watermills of many kinds. An early example of a very large water wheel is the still extant wheel at the early 13th century Real Monasterio de Nuestra Senora de Rueda, a Cistercian monastery in the Aragon region of Spain. Grist mills (for corn) were undoubtedly the most common, but there were also sawmills, fulling mills and mills to fulfil many other labour-intensive tasks. The water wheel remained competitive with the steam engine well into the Industrial Revolution. At around the 8th to 10th century, a number of irrigation technologies were brought into Spain and thus introduced to Europe. One of those technologies is the Noria, which is basically a wheel fitted with buckets on the peripherals for lifting water. It is similar to the undershot water wheel mentioned later in this article. It allowed peasants to power watermills more efficiently. According to Thomas Glick"s book, Irrigation and Society in Medieval Valencia, the Noria probably originated from somewhere in Persia. It has been used for centuries before the technology was brought into Spain by Arabs who had adopted it from the Romans. Thus the distribution of the Noria in the Iberian peninsula "conforms to the area of stabilized Islamic settlement".Spaniards, the technology spread to the New World in Mexico and South America following Spanish expansion

The type of water wheel selected was dependent upon the location. Generally if only small volumes of water and high waterfalls were available a millwright would choose to use an overshot wheel. The decision was influenced by the fact that the buckets could catch and use even a small volume of water.

Harnessing water-power enabled gains in agricultural productivity, food surpluses and the large scale urbanization starting in the 11th century. The usefulness of water power motivated European experiments with other power sources, such as wind and tidal mills.canals, put Europe on a hydraulically focused path, for instance water supply and irrigation technology was combined to modify supply power of the wheel.feudal state.

The water mill was used for grinding grain, producing flour for bread, malt for beer, or coarse meal for porridge.fulling mill, which was used for cloth making. The trip hammer was also used for making wrought iron and for working iron into useful shapes, an activity that was otherwise labour-intensive. The water wheel was also used in papermaking, beating material to a pulp. In the 13th century water mills used for hammering throughout Europe improved the productivity of early steel manufacturing. Along with the mastery of gunpowder, waterpower provided European countries worldwide military leadership from the 15th century.

Millwrights distinguished between the two forces, impulse and weight, at work in water wheels long before 18th-century Europe. Fitzherbert, a 16th-century agricultural writer, wrote "druieth the wheel as well as with the weight of the water as with strengthe [impulse]".Leonardo da Vinci also discussed water power, noting "the blow [of the water] is not weight, but excites a power of weight, almost equal to its own power".laws of force. Evangelista Torricelli"s work on water wheels used an analysis of Galileo"s work on falling bodies, that the velocity of a water sprouting from an orifice under its head was exactly equivalent to the velocity a drop of water acquired in falling freely from the same height.

The water wheel was a driving force behind the earliest stages of industrialization in Britain. Water-powered reciprocating devices were used in trip hammers and blast furnace bellows. Richard Arkwright"s water frame was powered by a water wheel.

The most powerful water wheel built in the United Kingdom was the 100 hp Quarry Bank Mill water wheel near Manchester. A high breastshot design, it was retired in 1904 and replaced with several turbines. It has now been restored and is a museum open to the public.

The biggest working water wheel in mainland Britain has a diameter of 15.4 m (51 ft) and was built by the De Winton company of Caernarfon. It is located within the Dinorwic workshops of the National Slate Museum in Llanberis, North Wales.

The largest working water wheel in the world is the Laxey Wheel (also known as Lady Isabella) in the village of Laxey, Isle of Man. It is 72 feet 6 inches (22.10 m) in diameter and 6 feet (1.83 m) wide and is maintained by Manx National Heritage.

During the Industrial Revolution, in the first half of the 19th century engineers started to design better wheels. In 1823 Jean-Victor Poncelet invented a very efficient undershot wheel design that could work on very low heads, which was commercialized and became popular by late 1830s. Other designs, as the Sagebien wheel, followed later. At the same time Claude Burdin was working on a radically different machine which he called turbine, and his pupil Benoît Fourneyron designed the first commercial one in the 1830s.

Development of water turbines led to decreased popularity of water wheels. The main advantage of turbines is that its ability to harness head is much greater than the diameter of the turbine, whereas a water wheel cannot effectively harness head greater than its diameter. The migration from water wheels to modern turbines took about one hundred years.

Water wheels were used to power sawmills, grist mills and for other purposes during development of the United States. The 40 feet (12 m) diameter water wheel at McCoy, Colorado, built in 1922, is a surviving one out of many which lifted water for irrigation out of the Colorado River.

Two early improvements were suspension wheels and rim gearing. Suspension wheels are constructed in the same manner as a bicycle wheel, the rim being supported under tension from the hub- this led to larger lighter wheels than the former design where the heavy spokes were under compression. Rim-gearing entailed adding a notched wheel to the rim or shroud of the wheel. A stub gear engaged the rim-gear and took the power into the mill using an independent line shaft. This removed the rotative stress from the axle which could thus be lighter, and also allowed more flexibility in the location of the power train. The shaft rotation was geared up from that of the wheel which led to less power loss. An example of this design pioneered by Thomas Hewes and refined by William Armstrong Fairburn can be seen at the 1849 restored wheel at the Portland Basin Canal Warehouse.

Australia has a relatively dry climate, nonetheless, where suitable water resources were available, water wheels were constructed in 19th-century Australia. These were used to power sawmills, flour mills, and stamper batteries used to crush gold-bearing ore. Notable examples of water wheels used in gold recovery operations were the large Garfield water wheel near Chewton—one of at least seven water wheels in the surrounding area—and the two water wheels at Adelong Falls; some remnants exist at both sites.Walhalla once had at least two water wheels, one of which was rolled to its site from Port Albert, on its rim using a novel trolley arrangement, taking nearly 90 days.water wheel at Jindabyne, constructed in 1847, was the first machine used to extract energy—for flour milling—from the Snowy River.

The early history of the watermill in India is obscure. Ancient Indian texts dating back to the 4th century BC refer to the term cakkavattaka (turning wheel), which commentaries explain as arahatta-ghati-yanta (machine with wheel-pots attached). On this basis, Joseph Needham suggested that the machine was a noria. Terry S. Reynolds, however, argues that the "term used in Indian texts is ambiguous and does not clearly indicate a water-powered device." Thorkild Schiøler argued that it is "more likely that these passages refer to some type of tread- or hand-operated water-lifting device, instead of a water-powered water-lifting wheel."

According to Greek historical tradition, India received water-mills from the Roman Empire in the early 4th century AD when a certain Metrodoros introduced "water-mills and baths, unknown among them [the Brahmans] till then".ancient India, predating, according to Pacey, its use in the later Roman Empire or China,

Around 1150, the astronomer Bhaskara Achārya observed water-raising wheels and imagined such a wheel lifting enough water to replenish the stream driving it, effectively, a perpetual motion machine.Arabic and Persian works. During medieval times, the diffusion of Indian and Persian irrigation technologies gave rise to an advanced irrigation system which bought about economic growth and also helped in the growth of material culture.

After the spread of Islam engineers of the Islamic world continued the water technologies of the ancient Near East; as evident in the excavation of a canal in the Basra region with remains of a water wheel dating from the 7th century. Hama in Syria still preserves some of its large wheels, on the river Orontes, although they are no longer in use.Murcia in Spain, La Nora, and although the original wheel has been replaced by a steel one, the Moorish system during al-Andalus is otherwise virtually unchanged. Some medieval Islamic compartmented water wheels could lift water as high as 30 metres (100 ft).Muhammad ibn Zakariya al-Razi"s Kitab al-Hawi in the 10th century described a noria in Iraq that could lift as much as 153,000 litres per hour (34,000 imp gal/h), or 2,550 litres per minute (560 imp gal/min). This is comparable to the output of modern norias in East Asia, which can lift up to 288,000 litres per hour (63,000 imp gal/h), or 4,800 litres per minute (1,100 imp gal/min).

The industrial uses of watermills in the Islamic world date back to the 7th century, while horizontal-wheeled and vertical-wheeled water mills were both in widespread use by the 9th century. A variety of industrial watermills were used in the Islamic world, including gristmills, hullers, sawmills, shipmills, stamp mills, steel mills, sugar mills, and tide mills. By the 11th century, every province throughout the Islamic world had these industrial watermills in operation, from al-Andalus and North Africa to the Middle East and Central Asia.crankshafts and water turbines, gears in watermills and water-raising machines, and dams as a source of water, used to provide additional power to watermills and water-raising machines.factory complexes built in al-Andalus between the 11th and 13th centuries.

The engineers of the Islamic world developed several solutions to achieve the maximum output from a water wheel. One solution was to mount them to piers of bridges to take advantage of the increased flow. Another solution was the shipmill, a type of water mill powered by water wheels mounted on the sides of ships moored in midstream. This technique was employed along the Tigris and Euphrates rivers in 10th-century Iraq, where large shipmills made of teak and iron could produce 10 tons of flour from corn every day for the granary in Baghdad.flywheel mechanism, which is used to smooth out the delivery of power from a driving device to a driven machine, was invented by Ibn Bassal (fl. 1038–1075) of Al-Andalus; he pioneered the use of the flywheel in the saqiya (chain pump) and noria.Al-Jazari in the 13th century and Taqi al-Din in the 16th century described many inventive water-raising machines in their technological treatises. They also employed water wheels to power a variety of devices, including various water clocks and automata.

A recent development of the breastshot wheel is a hydraulic wheel which effectively incorporates automatic regulation systems. The Aqualienne is one example. It generates between 37 kW and 200 kW of electricity from a 20 m3 (710 cu ft) waterflow with a head of 1 to 3.5 m (3 to 11 ft).

Overshot (and particularly backshot) wheels are the most efficient type; a backshot steel wheel can be more efficient (about 60%) than all but the most advanced and well-constructed turbines. In some situations an overshot wheel is preferable to a turbine.

The development of the hydraulic turbine wheels with their improved efficiency (>67%) opened up an alternative path for the installation of water wheels in existing mills, or redevelopment of abandoned mills.

The kinetic energy can be accounted for by converting it into an equivalent head, the velocity head, and adding it to the actual head. For still water the velocity head is zero, and to a good approximation it is negligible for slowly moving water, and can be ignored. The velocity in the tail race is not taken into account because for a perfect wheel the water would leave with zero energy which requires zero velocity. That is impossible, the water has to move away from the wheel, and represents an unavoidable cause of inefficiency.

The power is how fast that energy is delivered which is determined by the flow rate. It has been estimated that the ancient donkey or slave-powered quern of Rome made about one-half of a horsepower, the horizontal waterwheel creating slightly more than one-half of a horsepower, the undershot vertical waterwheel produced about three horsepower, and the medieval overshot waterwheel produced up to forty to sixty horsepower.

From the cross sectional area and the velocity. They must be measured at the same place but that can be anywhere in the head or tail races. It must have the same amount of water going through it as the wheel.

A parallel development is the hydraulic wheel/part reaction turbine that also incorporates a weir into the centre of the wheel but uses blades angled to the water flow.

The University of Southampton School of Civil Engineering and the Environment in the UK has investigated both types of Hydraulic wheel machines and has estimated their hydraulic efficiency and suggested improvements, i.e. The Rotary Hydraulic Pressure Machine. (Estimated maximum efficiency 85%).

These type of water wheels have high efficiency at part loads / variable flows and can operate at very low heads, < 1 m (3 ft 3 in). Combined with direct drive Axial Flux Permanent Magnet Alternators and power electronics they offer a viable alternative for low head hydroelectric power generation.

The Editors of Encyclopædia Britannica. "Waterwheel". Britannica.com. Encyclopædia Britannica, Inc. Retrieved 19 January 2018. |last1= has generic name (help)

Müller, G.; Wolter, C. (2004). "The breastshot waterwheel: design and model tests" (PDF). Proceedings of the Institution of Civil Engineers - Engineering Sustainability. 157 (4): 203–211. doi:10.1680/ensu.2004.157.4.203. ISSN 1478-4629 – via Semantic Scholar.

Wikander 2000, p. 395; Oleson 2000, p. 229It is no surprise that all the water-lifting devices that depend on subdivided wheels or cylinders originate in the sophisticated, scientifically advanced Hellenistic period, ...

Oleson 2000, pp. 235: The sudden appearance of literary and archaological evidence for the compartmented wheel in the third century B.C. stand in marked contrast to the complete absence of earlier testimony, suggesting that the device was invented not long before.

An isolated passage in the Hebrew Deuteronomy (11.10−11) about Egypt as a country where you sowed your seed and watered it with your feet is interpreted as an metaphor referring to the digging of irrigation channels rather than treading a waterwheel (Oleson 2000, pp. 234).

As for a Mesopotamian connection: Schioler 1973, p. 165−167: References to water-wheels in ancient Mesopotamia, found in handbooks and popular accounts, are for the most part based on the false assumption that the Akkadian equivalent of the logogram GIS.APIN was nartabu and denotes an instrument for watering ("instrument for making moist").As a result of his investigations, Laessoe writes as follows on the question of the saqiya: "I consider it unlikely that any reference to the saqiya will appear in ancient Mesopotamian sources." In his opinion, we should turn our attention to Alexandria, "where it seems plausible to assume that the saqiya was invented."

Adriana de Miranda (2007), Water architecture in the lands of Syria: the water-wheels, L"Erma di Bretschneider, pp. 48f, ISBN 978-8882654337 concludes that the Akkadian passages "are counched in terms too general too allow any conclusion as to the excat structure" of the irrigation apparatus, and states that "the latest official Chicago Assyrian Dictionary reports meanings not related to types of irrigation system".

Terry S, Reynolds, Stronger than a Hundred Men; A History of the Vertical Water Wheel. Baltimore; Johns Hopkins University Press, 1983. Robert, Friedel, A Culture of Improvement. MIT Press. Cambridge, Massachusetts. London, England. (2007). p. 33.

Smeaton, "An Experimental Inquiry Concerning the Natural Powers of Water and Wind to Turn Mills, and Other Machines, depending on Circular Motion," Royal Society, Philosophical Transactions of the Royal Society of London 51 (1759); 124–125

Davies, Peter; Lawrence, Susan (2013). "The Garfield water wheel: hydraulic power on the Victorian goldfields" (PDF). Australasian Historical Archaeology. 31: 25–32.

Wikander 2000, p. 400: This is also the period when water-mills started to spread outside the former Empire. According to Cedrenus (Historiarum compendium), a certain Metrodoros who went to India in c. A.D. 325 "constructed water-mills and baths, unknown among them [the Brahmans] till then".

Gies, Frances; Gies, Joseph (1994). Cathedral, Forge, and Waterwheel: Technology and Invention in the Middle Ages. HarperCollins Publishers. p. 115. ISBN 0060165901.

Donners, K.; Waelkens, M.; Deckers, J. (2002), "Water Mills in the Area of Sagalassos: A Disappearing Ancient Technology", Anatolian Studies, Anatolian Studies, Vol. 52, vol. 52, pp. 1–17, doi:10.2307/3643076, JSTOR 3643076, S2CID 163811541

Murphy, Donald (2005), Excavations of a Mill at Killoteran, Co. Waterford as Part of the N-25 Waterford By-Pass Project (PDF), Estuarine/ Alluvial Archaeology in Ireland. Towards Best Practice, University College Dublin and National Roads Authority

Oleson, John Peter (1984), Greek and Roman Mechanical Water-Lifting Devices: The History of a Technology, University of Toronto Press, ISBN 978-90-277-1693-4

Quaranta Emanuele, Revelli Roberto (2015), "Performance characteristics, power losses and mechanical power estimation for a breastshot water wheel", Energy, Energy, Elsevier, 87: 315–325, doi:10.1016/j.energy.2015.04.079

Oleson, John Peter (2000), "Water-Lifting", in Wikander, Örjan (ed.), Handbook of Ancient Water Technology, Technology and Change in History, vol. 2, Leiden: Brill, pp. 217–302, ISBN 978-90-04-11123-3

Reynolds, T.S. (1983) Stronger Than a Hundred Men: A History of the Vertical Water Wheel, Johns Hopkins studies in the history of technology: New Series 7, Baltimore: Johns Hopkins University Press, ISBN 0-8018-2554-7

Siddiqui, Iqtidar Husain (1986). "Water Works and Irrigation System in India during Pre-Mughal Times". Journal of the Economic and Social History of the Orient. 29 (1): 52–77. doi:10.1163/156852086X00036.

Wikander, Örjan (2000), "The Water-Mill", in Wikander, Örjan (ed.), Handbook of Ancient Water Technology, Technology and Change in History, vol. 2, Leiden: Brill, pp. 371–400, ISBN 978-90-04-11123-3

Wilson, Andrew (1995), "Water-Power in North Africa and the Development of the Horizontal Water-Wheel", Journal of Roman Archaeology, vol. 8, pp. 499–510

Illustration 4. Transformation of rotary motion into linear motion can be achieved by having a cam on the axle of the wheel (drawing from Scientific American).

Korean Peninsula is a mountainous region where a significant portion of the landscape is shaped by fast-flowing rivers. Given this basic geographical fact about Korea, it would be reasonable to assume that the Koreans would have actively utilized the water as an energy source. In the past when the steam engines and electricity did not exist, one of the most popular methods of generating energy was through the usage of the waterwheel. Therefore, it would be expected that Koreans would have built many waterwheels to take advantage of the numerous rivers that flowing at perfect rates to rotate them. Surprisingly, one can completely undermine this assumption by simply traveling around Korean countryside. Figure 1 on the left side represents the typical type of waterwheel found in current day Korea. Although this waterwheel looks fine at a glance, it has one major problem. The water has to move uphill in order to rotate the wheel, a phenomenon which goes against the natural law of gravitation. As shown in this example, many waterwheels in Korea nowadays are merely decorative, technically not functional. Moreover, only few waterwheels from the past still stand as historical remnants. Only two waterwheels are currently registered as the official Korean historical heritages. This small number does suggest a significant trend. It implies that the Koreans had little interest in preserving traditional waterwheels that presumably have been considered not that important. This implication ultimately leads to a claim that the waterwheels did not play a major role in Korean history. In contrast, "China during Song Dynasty was on the verge of industrial revolution when its waterwheel technology had reached its zenith" (1). The major force that drove the industrial revolution in Europe before the invention of steam engine was the waterwheels tied to machines through belts. In this historical context, there exists an obvious discrepancy between how the Koreans treated the waterwheel technology and how the Chinese and Europeans treated it.

The purpose of this research is to comparatively analyze the history of waterwheel in mainly three regions: Korea, China and Europe in general. Although the history of the waterwheel dates back to ancient Rome, or even further back, this paper puts significant emphasis on the periods from 960 when Song Dynasty and Goryeo Dynasty flourished in China and Korea respectively. Please understand that there may exist gaps between each periods addressed in this paper. Some of the in-between history of waterwheel in China is purposely omitted to maintain a focus. Because this research focuses mainly on the interaction between China and Korea, the history of waterwheel in Europe is only briefly mentioned to establish a balanced comparison. The history of waterwheel in Japan is also briefly mentioned because there was a major exchange of waterwheel technology between Korean and Japan during the Japanese invasion of Korea in the 16th century. However, Japan is not one of the main regions addressed in this paper because the influence was ephemeral and not continuous throughout history. Through analytic comparison of these three regions, this research ultimately aims to answer three questions listed below.

2) Why did the advanced waterwheel technology of China not spread to Goryeo and Joseon, despite their intimate cultural and military affiliation with China?

The paper is first categorized by the three main regions(China, Korea, Europe). In each chapter, the history of the waterwheel is narrated chronologically, covering a general history but emphasizing certain periods. Most importantly, in chapter V, the different histories of each region will be comparatively analyzed to answer the questions mentioned above.

(Korea) The definition is similar to that in Europe, but it technically includes only the wheels that are used for irrigational purpose. However, this term is often vaguely used by Korean scholars to mean any machine that contains a rotating wheel associated with water power (2). The Spanish called this type of irrigational waterwheel a noria - "a machine for lifting water into a small aqueduct, either for the purpose of irrigation or, in at least one known instance, to feed seawater into a saltern."

A Korean traditional watermill that does not use a waterwheel but instead uses a wooden lever that is pulled down by a water container. The container is constantly filled with water until the water inside is eventually released due to the gravity and pulls the lever down. The lever goes back up slowly as the water inside the container empties. The repeated cycle of the lever moving up and down pounds the grain placed in a hole as shown in the above photo.

Traditional Korean terminology for the waterwheel used for irrigation, especially in the salt ponds. Very similar to "Noria" and "Dragon-bone wheel" in style.

Although this paper mainly deals with the advanced water-power technologies in Song Dynasty, it is necessary to trace their origins from the ancient time, for it is unreasonable to expect a set of advanced technologies to be spontaneously developed in only few hundred years of time.

Xin Lun written by Huan Tan, the first text that mentions the existence of waterwheels in China, implies that the waterwheel was already in widespread use in China by 1st century. It also mentions a mythological figure Fu Xi who lived in about 20 AD. He developed a tool that very much resembled the pestle and mortar - very essential parts that probably evolved into the trip hammer (mentioned in the history of waterwheel in Song Dynasty). Although the mention of such devices is merely mythological, it is inappropriate to disregard the possibility that such tools actually existed in ancient China.

According to Xin Lun, Du Shi, the engineer and Prefect of Nanyang, in 31 AD, used waterwheel to develop a machine that powers an automated furnace to create cast iron. Joseph Needham"s supports this by saying,

"Those who smelted and cast already had the push-bellows to blow up their charcoal fires, and now they were instructed to use the rushing of the water to operate it ... Thus the people got great benefit for little labor. They found the "water-powered bellows" convenient and adopted it widely".

Chinese not only invented technological waterwheels but also developed waterwheels for agriculture. The Dragon-bone wheel, Chinese traditional irrigational waterwheel, was invented during Han Dynasty

As shown in the above examples, the extraordinary usages of ancient Chinese waterwheel stretched into various fields including science, metallurgy, and agriculture.

During Tang Dynasty, the water-mill spread to other countries under Chinese influence, including Korea, Japan and Tibet (7). But it seems like only the agriculture function of the waterwheel got transferred to these regions, for none of the records from these regions during that time period mentions any manfacuring function of the waterwheels.

However, they were adept at using water as their energy source. The photo above is an automated bellow powered by a horizontal waterwheel. While the conventional bellow required a person pumping air with his own hands and feet, this type did not need any human labor. Not only it helped reduce the burden of Chinese workers, it also made it possible for Chinese to deal with more sophisticated metallurgy, for the repeated influx of air into the bellow raised up the temperature inside higher than ever before. One noticeable structure in this bellow is the linear structure that transforms the rotational motion of the waterwheel rotating along with the river located below. The fact that the ancient Chinese already had almost identical device is something to be noted.

More remarkably, there is additional evidence which indicates that the Song could manufacture metal. The below is a trip hammer connected to a long shaft rotating with a waterwheel.

The waterwheel could produce 400kg of force per single rotation. So these could not only crush grain, but also pound metal. This technology is also a revival of ancient Chinese thought as mentioned in the previous chapter. While the ancient people did not provide pictorial models for such devices, later Chinese scholars were generous enough to provide such explanation for their inventions. These mega waterwheels still remain in some regions in China. Chinese during the Song Dynasty could both melt and pound metals in industrial scale - a crucial prerequisite of industrial revolution.

"Particularly remarkable was the use, at least as early as +1313, of water-power for textile machinery. The Nung Shu illustrates a spinning-mill in which we see a vertical undershot waterwheel and a large driving wheel with a belt-drive on the same shaft working a multiple-bobbin spinning-machine for hemp and ramie, perhaps also for cotton�� This should be enough to give pause to any economic historian, especially as Wang Chen clearly says that such installations were common in his time." (11) The textile machinery is shown on the figure above.

Gearing technology is another key to industrial revolution, for it allows intricate operation of metal machines. Also, gears play a crucial role in handling the magnitude of power applied to certain machines. They also help machines to operate in larger scales. It is surprising that the Chinese applied such technologies to their waterwheels. Although the gearing technology had been existing since ancient times, nobody was faster than the Chinese in combining waterwheel and gears (Europeans began to attach gears to waterwheels in 13th century, a century after Song Dynasty). Nine Millstones are attached to the waterwheel below, rotating simultaneously to pound grains. In other words, The Chinese knew how to create maximum efficiency with limited power supply.

Gearing technology was not the only skill that Chinese had mastered. Su Sung, a renowned Chinese genius astronomer and engineer, devised the world"s first power-transmitting chain drive in his astronomical water-clock, which he claimed is an imitation the record of Zhang Heng"s water clock from ancient China. Below is an excerpt from Joseph Needham"s explanation of the water-clock.

The mechanical clockworks for Su Song"s astronomical tower featured a great driving-wheel that was 11 feet in diameter, carrying 36 scoops on its circumference, into each of which water would pour at uniform rate from the "constant-level tank. The main driving shaft of iron, with its cylindrical necks supported on iron crescent-shaped bearings, ended in a pinion which engages with a gear-wheel at the lower end of the main vertical transmission-shaft��

(Su Song"s) clockwork, driven by a water-wheel, and fully enclosed within the tower, rotated an observational armillary sphere on the top platform and a celestial globe in the upper story. Its time-announcing function was further fulfilled visually and audibly by the performances of numerous jacks mounted on the eight superimposed wheels of a time-keeping shaft and appearing at windows in the pagoda-like structure at the front of the tower. Within the building, some 40 ft. high, the driving-wheel was provided with a special form of escapement, and the water was pumped back into the tanks periodically by manual means. The time-annunciator must have included conversion gearing, since it gave "unequal" as well as equal time signals, and the sphere probably had this. Su Sung"s treatise on the clock, the Hsin I Hsiang Fa Yao, constitutes a classic of horological engineering (13)

As shown in the above enumeration of technologies, Song Dynasty had almost everything ready for industrial revolution. They had all the materialistic prerequisites: oil drilling technology, metal manufacturing, and gearing. As mentioned in the later section "Brief History of waterwheel in Europe", what they had is very similar to the technologies found in Europe just before it reached industrial revolution. Some of the inventions, such as the gearing technology and the Su Sung water clock, were perhaps more advanced than the contemporary European technologies. Then what caused such huge big difference? The answer will be addressed in section V : Comparative Analysis.

By the Yuan (1271-1368) and Ming (1368-1644) dynasties, the waterwheel technology had further improved. Nonetheless, there was no more distinct development of Chinese waterwheels after the Yuan and Ming dynasties. What is observed is a shift in the usage of waterwheels from the verge of industrial revolution to merely agricultural state. Although some records of technological waterwheels remain from Qing Dynasty, most of them are simply about the agriculture waterwheels that had been used since ancient times.

After 16th century, Chinese began to adopt the European style irrigational waterwheel named "diancha" for irrigating water. This is a re-adoption of a technology that was long forgotten by the Chinese. They already had a very similar style waterwheel called the "dragon-bone wheel" in Han Dynasty and Song Dynasty. Unfortunately, the reason why such technologies had to be readopted is not clearly answered. The frequent changes of ruling authority and the foreign invasions might serve as a reason that caused the regression of waterwheel technology in China.

In Korean history, the word "waterwheel" first appears in a book from Goryeo Dynasty. According to Goryeosa (the history of Goryeo) (17), in 1362, one liege named Baek Mun Bo of king Gongmin suggested that the adoption of waterwheel technology from the Jiangnan province of China would be helpful for the farmers who often struggle with irrigation during drought periods. He explains to the king that the advantage of Chinese farmers over drought. He said, "the farmers in Jiangnan are not afraid of droughts because they have the waterwheel. Our farmers struggle during droughts because they don"t know how to irrigate water from the river just a meter below the farmland. It would be a great help for the farmers if we would adopt the waterwheel from Jiangnan and enlighten our farmers with it so that they can fight the droughts more easily" (18) . The waterwheel which Baek Mun Bo observed should have been the chain-wheel type, called dragon-bone wheel, for these type of waterwheels is still used in modern day Jiangnan. Although it would have been reasonable for the king to take some action upon such request, not much is known about how the king reacted to this proposal afterward. No documents of Goryeo after 1362 show any trace of waterwheel.

About a century earlier than 1362, there is a record of the King and Queen sightseeing a waterwheel in 1276, but this records lacks any detailed support. (19)

There is a source that suggests the first record of waterwheel is even earlier. The History of Japan suggests that one monk from Goryeo named Dam Jing first introduced the watermill to Japan in 610 (20). In fact, Joseph Needham insinuates this incident in his book by saying, "During the Thang, the water-mill had radiated to other countries in the Chinese culture-area, to Japan (via Korea) in +610 and +670 and to Tibet about +641." (21)

However, this claim is less credible because the original primary source uses the term "Yeon-ae" which can basically indicate any type of mill powered by animals, water, wind and etc. But the record does itself explain that the mill was somewhat associated with water.

More records of the waterwheel are found in the documents from Joseon Dynasty. According to Joseon Wangjo Sillok (Annals of the Joseon Dynasty), King Taejong in December 1406 encouraged his people to build the waterwheel and supported them by constructing few waterwheels per each town as samples and ordering the local government officials to construct additional waterwheels (22). This incident was the first time in Korean history when the government "officially" encouraged its people to utilize waterwheel. That it was supported by the king is also a significant fact. However, it is not clear whether the waterwheel they tried to adopt was from China or Japan. Because the waterwheel technology had already spread from China to Japan long ago, and because Joseon and Japan had already established a diplomatic trade relationship by sending ambassadors in 1404, Koreans could have adopt either type of waterwheel from these two countries.

The next record of the waterwheel appears again in the records of King Sejong. Park Seo Sang, a Korean ambassador who visited Japan in 1429 brought back a mimic diagram of a Japanese waterwheel. Park did not officially gain the model from the Japanese government. Rather, he was motivated to remake a similar model after his companions had observed the automated waterwheel of the Japanese farmers. While the Japanese waterwheels were completely automatic, the old waterwheels of Korea needed both human power and the flow of water(Dragon-bone wheel from Jiangnan). Upon Park"s vehement request to spread this type of waterwheel among farmers, Sejong actively carried a plan to popularize the usage of waterwheel in Joseon. Koreans distinguished this waterwheel by calling the new Japanese waterwheel "Wae-sucha" and the old Chinse waterwheel "Dang-sucha" (23). Sejong ran few test cases to confirm whether these waterwheels were actually effective or not. These tests proved that the waterwheel was greatly effective for irrigation. In 1431, Sejong sent mini-models of this waterwheel to the local rulers and ordered them to build waterwheels according to those models. He also assigned local officials who exclusively dealt with the construction of new waterwheels. The construction of the old type of waterwheel from Taejong"s period also continued along with the new type. The fact that Sejong assigned officials designated only for the spread of waterwheel shows his serious attitude toward promoting the waterwheel to a country-wide trend. Sejong even promised to give royal awards to farmers who successfully utilize the new waterwheel technology (24).

However, Sejong faced two major problems in the process of carrying on this project. First, the rivers which Sejong intended to irrigate the water from were slow-flowing wide rivers. Because the Japanese model was suited for fast-flowing narrow rivers, the slow flow of the Korean rivers was not powerful enough to rotate the wheels automatically. Therefore, a device on which a person could generate additional energy by pedaling was attached to the model, turning the automated waterwheel to not-automated. The other problem Sejong had to deal with was the soil. The Korean soil soaked water so well that even though the irrigation of water from the river up to the farm land was successful, the farm land failed to contain the water long enough for farming. Sejong"s waterwheel project ultimately ended after the officials reported him of this inefficiency.

The efforts to develop the irrigational waterwheels continued throughout Joseon dynasty, but the results were never as effective as that of the other irrigation methods popular in Joseon. In 1488, Choi-Bu, a government official under Seongjong, tested new Chinese waterwheel in Gyeongi Province. In 1502, Yeonsan-gun denied Kim Yik Kyeong"s request to build additional waterwheels (25). Yeonsan-gun claimed three reasons for not constructing anymore waterwheels. "First, waterwheels are difficult to control and manage. Second, the waterwheels become futile when severe droughts take place. Third, farmers do not need to irrigate water by waterwheel if it there is enough rain."

Although these claims partially constitute Joseon"s reluctance to develop waterwheels, the major reason was the dominant popularity of the other irrigation methods. In 16th century, Cheon-bang and Je-eon were the two popular methods used for irrigation. Cheon-bang is an irrigation method which utilizes series of small dams, and Je-eon is the irrigation method which uses the water reservoirs. Because these two methods were so popular and well-working, the kings paid little attention to developing any other type of technology like the waterwheel.

In 1650, Hyojong, a prince who was kidnapped to live in China when the Qing invaded Joseon, expressed his will to promote the Qing style waterwheel when he came back to Joseon to become the king. And in 1783, Seo Ho Su suggested King Jeongjo to adopt Yongmi-cha (Archimedean screw), a type of western waterwheel introduced by a western priest by the name of Sabbathino de Ursis. S. de Ursis was a priest who came to preach China in 1606 and helped Chinese write books on a Western technology. So the Koreans didn"t necessarily learn directly from him but from the books that Chinese had written based on his knowledge. (26) This type of waterwheel was generally of better quality than the Chinese waterwheels and was better suited for larger rivers. Jeongjo"s interest in the waterwheels continued. He attempted to install few waterwheels in his Hwaseong Fortress, but these attempts failed due to financial issues. This suggests that the construction of the waterwheel was not his first priority in building his fortress. Although many books like Haedongnongseo (a book on Korean agriculture in general) (27) from this period mention about the waterwheels, though many Joseon scholars were fascinated by the enlightened ideas of the West, none of the theoretical designs were actually used to construct real waterwheels. (24)

After the 17th century, the government somewhat continueed to promote the waterwheel, but none of these trials had a significant impact on modern Joseon society as did the attempts in previous centuries. What actually takes place instead, is the shift of focus from the waterwheel to the watermill. While the previous attempts focused exclusively on the irrigational function of the waterwheel, Joseon kings from the 17th century shift their gears toward the watermill for pounding grains. The reasons behind this shift will be addressed in an upcoming chapter.

As mentioned in the previous chapters, there were a number of attempts to promote the usage of the waterwheel throughout Joseon dynasty. In general, there were several discrepancies between the conditions of Korea and China that determined the success or failure of adopting the waterwheel technology. There were roughly three reasons why such attempts to spread the waterwheel turned out to be futile in the Korean peninsula. "First, the soil of the farmland was different from that of China. Second, the irrigational condition of the water sources was different. Third, the agricultural condition and economic problem that existed throughout Joseon Dynasty" (30).

The locations where the Chinese utilized the irrigational waterwheel were mainly centered on regions with vast plain and wide rivers like Jiangnan, through which the Yangtze River passes by. The soil in such regions mainly consisted of clay which did not absorb much water. The rivers always had a huge amount of water flowing fast throughout the year. The Chinese did not use the waterwheels in mountainous regions. However, most of rivers in Korea are slow-flowing and almost seem to be stationary in some regions. During droughts, the rivers completely dried up, making it impossible for the farmers to use their waterwheels. During summer, there were many cases when it rained so much that the farmers did not need the waterwheels at all to irrigate any additional water to their farms. These reasons are supported by the cases of Park Seo Sang"s and Kim Yik Kyeong"s case that were mentioned in the previous chapter.

The primary reason that Koreans did not utilize the waterwheel for irrigational purpose was mainly the geographical condition of the Korean Peninsula. While the rivers over-flew during summer, they were too shallow in the other seasons to use waterwheels; the rivers were inconsistent. The dynamic change of climate throughout the year and the vulnerability of the rivers made the other irrigation methods in Korea more effective than the waterwheel. Because many rivers flowing in mountainous regions are shallow and inconsistent, they were not suitable to run the waterwheels. Consistency was the key in using the waterwheel which the Koreans did not have. But this still does not answer the question why they did not apply this waterwheel technology to any other machines like the engineers of Song Dynasty did.

Then why did such attempts persist throughout the 500 years of Joseon Dynasty? It would be normal to give up on a policy if it continuously fails. In the late Joseon Dynasty, the farmers adopted a new type of farming method called Yi-Ang bup which required much more water to be irrigated than the traditional way of farming. The need to irrigate more amount of water eventually led to attempts to develop and utilize the waterwheel to some extent.

Moreover, the introduction of the new farming method led the waterwheel to change its form to the watermill, so called Mullebanga. As the production of food increased due to the new farming method in 17th century, there were more grains to be grinded. Although the existing types of mills had no problem grinding before 17th century, they weren"t enough once the food production had increased. The number of mills powered by oxen decreased because the farmers needed the oxen to work on the farm land instead, and the number of oxen was very limited. Because Mullebanga was 17 times more effective than the traditional mills, it enabled the farmers to focus more on "farming" than grinding their product. In general, Mullebanga greatly contributed to the increase of agricultural production of Joseon since the 17th century. Although waterwheel was thrown off by other irrigational methods in Korea, the other irrigational infrastructure such as dams and water reservoirs were very helpful for providing the adequate water source for the watermills.

As engines operated by fuel and electricity were introduced to the farmers in 20th century, the traditional watermills gradually lost their place in Korean agriculture.

The traditional watermill was modernized by 1930. Although the wheel that generates the power maintained the same style even in the modern time, the structure inside the watermills completely changed with modernization. Although the traditional watermills were connected to wooden levers that repeatedly went up and down, the modern watermills were linked to belts that connected various machines together.

Currently, only two watermills are registered as the official Korean historical heritage. This chapter explores these two watermills as the representative of modern Korean waterwheels.

One of the two Korean watermills addressed in this paper is located at Sil-li, Dogye-eup, exact GPS location of being 37 11"020 1290874. Sil-li watermill was designated as a national historical heritage in 1975. The date when it was built is unknown, but it is a typical 18th century Korean watermill. According to the locals, until 2003, the mill was still in use by the person who built it, so it would be reasonable to assume that it was built around early 1900s.

A trip to this watermill suggested how Koreans disregard the true value of their traditional watermills. The below is an observation from a trip to Sil-li waterwheel in May 26th, 2013 and July 7th, 2013.

Although the roads to historical sites are usually well-guided, it wasn"t the case for this mill. Because it was hidden behind the guard rail of the road, it was necessary to pass by the same place thrice before discovering that the watermill was actually there. The guiding plates were inaccurate, and the mill seemed to be very minor compared to the other parts of the historical sight.

The above photo is the Sil-li waterwheel. The wheel part has recently been renovated, but there was no water flowing to actually rotate it, for the waterway was blocked by large stones. If there were any water, the water would have flowed in the upright direction and the wheel would have rotated forward. However, the axis which connects the wheel and the mill wasn"t properly set. Also, the mill didn"t have a mill stone. Instead, it had a T-Shaped mortar that grinded