An embankment dam is a large artificial dam. It is created by the placement and compaction of a complex semi-plastic mound of various compositions of soil, clay, or rock, it has a semi-pervious waterproof natural covering for a dense, impervious core. This makes such a dam impervious to seepage erosion; such a dam is composed of fragmented independent material particles. The friction and interaction of particles binds the particles together into a stable mass rather than by the use of a cementing substance. Embankment dams come in two types: the earth-filled dam made of compacted earth, the rock-filled dam. A cross-section of an embankment dam shows a shape like hill. Most have a central section or core composed of an impermeable material to stop water from seeping through the dam; the core can be of concrete, or asphalt concrete. This dam type is a good choice for sites with wide valleys, they can be built on softer soils. For a rock-fill dam, rock-fill is blasted using explosives to break the rock.
Additionally, the rock pieces may need to be crushed into smaller grades to get the right range of size for use in an embankment dam. The building of a dam and the filling of the reservoir behind it places a new weight on the floor and sides of a valley; the stress of the water increases linearly with its depth. Water pushes against the upstream face of the dam, a nonrigid structure that under stress behaves semiplastically, causes greater need for adjustment near the base of the dam than at shallower water levels, thus the stress level of the dam must be calculated in advance of building to ensure that its break level threshold is not exceeded. Overtopping or overflow of an embankment dam beyond its spillway capacity will cause its eventual failure; the erosion of the dam's material by overtopping runoff will remove masses of material whose weight holds the dam in place and against the hydraulic forces acting to move the dam. A small sustained overtopping flow can remove thousands of tons of overburden soil from the mass of the dam within hours.
The removal of this mass unbalances the forces that stabilize the dam against its reservoir as the mass of water still impounded behind the dam presses against the lightened mass of the embankment, made lighter by surface erosion. As the mass of the dam erodes, the force exerted by the reservoir begins to move the entire structure; the embankment, having no elastic strength, would begin to break into separate pieces, allowing the impounded reservoir water to flow between them and removing more material as it passes through. In the final stages of failure the remaining pieces of the embankment would offer no resistance to the flow of the water and continue to fracture into smaller and smaller sections of earth or rock until these would disintegrate into a thick mud soup of earth and water. Therefore, safety requirements for the spillway are high, require it to be capable of containing a maximum flood stage, it is common for its specifications to be written such. A number of embankment dam overtopping protection systems have been developed.
These techniques include the concrete overtopping protection systems, timber cribs, sheet-piles and gabions, reinforced earth, minimum energy loss weirs, embankment overflow stepped spillways and the precast concrete block protection systems. Earth structure Gravity dam List of largest dams in the world Embankment dams Table of contents An introduction to embankment dams 100 Years of Embankment Dam Design and Construction in the U. S. Bureau of Reclamation
Concrete Portland cement concrete, is a composite material composed of fine and coarse aggregate bonded together with a fluid cement that hardens over time—most a lime-based cement binder, such as Portland cement, but sometimes with other hydraulic cements, such as a calcium aluminate cement. It is distinguished from other, non-cementitious types of concrete all binding some form of aggregate together, including asphalt concrete with a bitumen binder, used for road surfaces, polymer concretes that use polymers as a binder; when aggregate is mixed together with dry Portland cement and water, the mixture forms a fluid slurry, poured and molded into shape. The cement reacts chemically with the water and other ingredients to form a hard matrix that binds the materials together into a durable stone-like material that has many uses. Additives are included in the mixture to improve the physical properties of the wet mix or the finished material. Most concrete is poured with reinforcing materials embedded to provide tensile strength, yielding reinforced concrete.
Famous concrete structures include the Panama Canal and the Roman Pantheon. The earliest large-scale users of concrete technology were the ancient Romans, concrete was used in the Roman Empire; the Colosseum in Rome was built of concrete, the concrete dome of the Pantheon is the world's largest unreinforced concrete dome. Today, large concrete structures are made with reinforced concrete. After the Roman Empire collapsed, use of concrete became rare until the technology was redeveloped in the mid-18th century. Worldwide, concrete has overtaken steel in tonnage of material used; the word concrete comes from the Latin word "concretus", the perfect passive participle of "concrescere", from "con-" and "crescere". Small-scale production of concrete-like materials was pioneered by the Nabatean traders who occupied and controlled a series of oases and developed a small empire in the regions of southern Syria and northern Jordan from the 4th century BC, they discovered the advantages of hydraulic lime, with some self-cementing properties, by 700 BC.
They built kilns to supply mortar for the construction of rubble-wall houses, concrete floors, underground waterproof cisterns. They kept the cisterns secret; some of these structures survive to this day. In the Ancient Egyptian and Roman eras, builders discovered that adding volcanic ash to the mix allowed it to set underwater. German archaeologist Heinrich Schliemann found concrete floors, which were made of lime and pebbles, in the royal palace of Tiryns, which dates to 1400–1200 BC. Lime mortars were used in Greece and Cyprus in 800 BC; the Assyrian Jerwan Aqueduct made use of waterproof concrete. Concrete was used for construction in many ancient structures; the Romans used concrete extensively from 300 BC to a span of more than seven hundred years. During the Roman Empire, Roman concrete was made from quicklime, pozzolana and an aggregate of pumice, its widespread use in many Roman structures, a key event in the history of architecture termed the Roman Architectural Revolution, freed Roman construction from the restrictions of stone and brick materials.
It enabled revolutionary new designs in terms of both structural dimension. Concrete, as the Romans knew it, was a revolutionary material. Laid in the shape of arches and domes, it hardened into a rigid mass, free from many of the internal thrusts and strains that troubled the builders of similar structures in stone or brick. Modern tests show that opus caementicium had as much compressive strength as modern Portland-cement concrete. However, due to the absence of reinforcement, its tensile strength was far lower than modern reinforced concrete, its mode of application was different: Modern structural concrete differs from Roman concrete in two important details. First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the placement of aggregate, which, in Roman practice consisted of rubble. Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon the strength of the concrete bonding to resist tension.
The long-term durability of Roman concrete structures has been found to be due to its use of pyroclastic rock and ash, whereby crystallization of strätlingite and the coalescence of calcium–aluminum-silicate–hydrate cementing binder helped give the concrete a greater degree of fracture resistance in seismically active environments. Roman concrete is more resistant to erosion by seawater than modern concrete; the widespread use of concrete in many Roman structures ensured that many survive to the present day. The Baths of Caracalla in Rome are just one example. Many Roman aqueducts and bridges, such as the magnificent Pont du Gard in southern France, have masonry cladding on a concrete core, as does the dome of the Pantheon. After the Roman Empire, the use of burned lime and pozzolana was reduced until the technique was all but forgotten between 500 and the 14th century. From the 14th century to the mid-18th century, the use of cement returned; the Canal du Midi was built using concrete in 1670.
The greatest step forward in the modern use
Bryntail lead mine
Bryntail lead mine is a disused lead mine near Llanidloes in Powys, Wales. It is in the care of Cadw. There were three main shafts, Murray's, Gundry's and Western shaft; the majority of the scheduled buildings on the site are associated with Gundry's shaft, including a barytes mill, two crushing houses, ore bins, roasting ovens and water tanks. On the eastern dressing floor are jigger box placements, three buddles, two more ore bins and washing and picking floors. Other mine buildings include the manager's office, store buildings and a circular magazine, as well as the miners' footbridge. Photos of Bryntail lead mine and surrounding area on geograph Cadw visitor's page
A reservoir is, most an enlarged natural or artificial lake, pond or impoundment created using a dam or lock to store water. Reservoirs can be created in a number of ways, including controlling a watercourse that drains an existing body of water, interrupting a watercourse to form an embayment within it, through excavation, or building any number of retaining walls or levees. Defined as a storage space for fluids, reservoirs may hold gasses, including hydrocarbons. Tank reservoirs elevated, or buried tanks. Tank reservoirs for water are called cisterns. Most underground reservoirs are used to store liquids, principally either water or petroleum, below ground. Reservoir is most an enlarged natural or artificial lake. A dam constructed in a valley relies on the natural topography to provide most of the basin of the reservoir. Dams are located at a narrow part of a valley downstream of a natural basin; the valley sides act as natural walls, with the dam located at the narrowest practical point to provide strength and the lowest cost of construction.
In many reservoir construction projects, people have to be moved and re-housed, historical artifacts moved or rare environments relocated. Examples include the temples of Abu Simbel, the relocation of the village of Capel Celyn during the construction of Llyn Celyn, the relocation of Borgo San Pietro of Petrella Salto during the construction of Lake Salto. Construction of a reservoir in a valley will need the river to be diverted during part of the build through a temporary tunnel or by-pass channel. In hilly regions, reservoirs are constructed by enlarging existing lakes. Sometimes in such reservoirs, the new top water level exceeds the watershed height on one or more of the feeder streams such as at Llyn Clywedog in Mid Wales. In such cases additional side dams are required to contain the reservoir. Where the topography is poorly suited to a single large reservoir, a number of smaller reservoirs may be constructed in a chain, as in the River Taff valley where the Llwyn-on, Cantref and Beacons Reservoirs form a chain up the valley.
Coastal reservoirs are fresh water storage reservoirs located on the sea coast near the river mouth to store the flood water of a river. As the land based reservoir construction is fraught with substantial land submergence, coastal reservoir is preferred economically and technically since it does not use scarce land area. Many coastal reservoirs were constructed in Europe. Saemanguem in South Korea, Marina Barrage in Singapore and Plover Cove in China, etc are few existing coastal reservoirs. Where water is pumped or siphoned from a river of variable quality or size, bank-side reservoirs may be built to store the water; such reservoirs are formed by excavation and by building a complete encircling bund or embankment, which may exceed 6 km in circumference. Both the floor of the reservoir and the bund must have an impermeable lining or core: these were made of puddled clay, but this has been superseded by the modern use of rolled clay; the water stored in such reservoirs may stay there for several months, during which time normal biological processes may reduce many contaminants and eliminate any turbidity.
The use of bank-side reservoirs allows water abstraction to be stopped for some time, when the river is unacceptably polluted or when flow conditions are low due to drought. The London water supply system is one example of the use of bank-side storage: the water is taken from the River Thames and River Lee. Service reservoirs store treated potable water close to the point of distribution. Many service reservoirs are constructed as water towers as elevated structures on concrete pillars where the landscape is flat. Other service reservoirs can be entirely underground in more hilly or mountainous country. In the United Kingdom, Thames Water has many underground reservoirs, sometimes called cisterns, built in the 1800s, most of which are lined with brick. A good example is the Honor Oak Reservoir in London, constructed between 1901 and 1909; when it was completed it was said to be the largest brick built underground reservoir in the world and it is still one of the largest in Europe. This reservoir now forms part of the southern extension of the Thames Water Ring Main.
The top of the reservoir is now used by the Aquarius Golf Club. Service reservoirs perform several functions, including ensuring sufficient head of water in the water distribution system and providing water capacity to out peak demand from consumers, enabling the treatment plant to run at optimum efficiency. Large service reservoirs can be managed to reduce the cost of pumping, by refilling the reservoir at times of day when energy costs are low. Circa 3 000 BC, the craters of extinct volcanoes in Arabia were used as reservoirs by farmers for their irrigation water. Dry climate and water scarcity in India led to early development of stepwells and water resource management techniques, including the building of a reservoir at Girnar in 3000 BC. Artificial lakes dating to the 5th century BC have been found in ancient Greece; the artificial Bhojsagar lake in present-day Madhya Pradesh state of India, constructed in the 11th century, covered 650 square kilometres. In Sri Lanka large reservoirs were created by ancient Sinhalese kings in order to save the water for irrigation.
The famous Sri Lankan king Pa
Ystradgynlais is a town on the banks of the River Tawe in southwest Powys, is the second largest in the principal area and county of Powys. It is in the historic county of Brecknockshire; the place-name Ystradgynlais, meaning'vale of the river Cynlais' - Cynlais may be a personal name, or derive from cyn and glais - is first recorded in 1372. In the 1600s there were only a couple of houses by a pub. In 1801 there were only 993 residents in the town living in only 196 houses; the first documented written evidence of iron working in the area was at Ynyscedwyn and is of a deed of release dated 1729. By 1750 there were seven furnaces in south Wales, one of, at Ynyscedwyn; the first written evidence of coal workings in the area was in 1780 in Wauclawdd. Most of the coal dug up in the area was sent to the blast furnaces of the iron works. By 1790 the full extent of the mineral resources in the valley were better known and it was realised that to exploit these to the full, improved transport would be essential.
The greatest increase in population was from 1821-41 which coincides with the coming of George Crane and the development of the Ynyscedwyn Ironworks. By 1870 however the area's industrial development was in decline due to various economic factors. Although coal mining carried on in the area a few light industries have replaced the heavy industries. Ystradgynlais is one of the few areas within Brecknockshire which has a high proportion of Welsh-speakers. Ystradgynlais hosted the 1954 National Eisteddfod, an annual Welsh festival of literature and music; the century-old award-winning Ystradgynlais Public Band competed in the 2005 National Eisteddfod. Ystradgynlais's Parc-yr-Orsedd has a monument to the fallen heroes of both World Wars from Ystradgynlais, Cwmtwrch, Cwmgiedd and Coelbren. Dan yr Ogof caves are a short journey from the town centre, passing Craig-y-Nos Castle and country park; the caves are reputed to have once been the hideout of folk figure Twm Siôn Cati. Henrhyd Falls are nearby. Ysgol Maesydderwen.
Ystradgynlais is home to the Miners Welfare Hall and promoted as'The Welfare', which plays host to a cinema. It has a number of public houses. In 2016 The Stephen Lewis Tristars Aquathlon in Ystradgynlais won the Welsh triathlon event of the Year 2016 National Cycle Route 43 passes by the southern edge of the town on the line of the former Swansea Vale Railway which linked Swansea via the Neath and Brecon Railway at Coelbren with Brecon. Ystradgynlais railway station was operational from 1869 to 1923; the A4067 road ran through the town but was diverted in the 1970s onto a bypass route which follows the line of the former Swansea Canal. Thomas Levi was a Welsh, Calvinistic Methodist minister, literary figure who played a role in the political life of Wales. Born in Ystradgynlais he spent his life as minister of Tabernacl, Aberystwyth. Madame Adelina Patti, the renowned opera singer who lived at Craig y Nos Castle, was married in the parish church and her body lay there in state after her death.
Composer Daniel Protheroe, was born in Ystradgynlais and lived there prior to emigrating to Scranton, Pennsylvania. Tudor Thomas was born in Ystradgynlais. Thomas was an early specialist in corneal grafting, he was knighted in 1955 The Polish painter Josef Herman, spent 11 years living and painting in Ystradgynlais. William Lewis Thomas born in Ystradgynlais, was a rugby union and rugby league footballer of the 1930s, 1940s, he played club level rugby union for Ystradgynlais RFC, club level rugby league for Ystradgynlais RLFC Sir Goronwy Hopkin Daniel KCVO was a Welsh academic and civil servant. The novelist Menna Gallie was born here, wrote two novels based on the area, Strike for a Kingdom and The Small Mine John Howard Purnell OBE MA PhD ScD CChem FRSC was a Welsh chemist, he attended Maes y Dderwen County School in Ystradgynlais. In 1965 he became Professor of Physical Chemistry at University College, Swansea and he was president of the Royal Society of Chemistry between 1994 and 1996. Caerwyn Roderick Member of Parliament for Brecon and Radnor, 1970–79, was born in the town Julian Hopkin is a physician and medical teacher.
In 2004, he became the founding Head of the new Medical School at Swansea University. He is Professor of Experimental Medicine at Swansea University Medical School and Honorary Physician at the Abertawe-Bro-Morgannwg University Hospital. Received a CBE in 2011 for his services to medicine Rowan Williams, the former Archbishop of Canterbury grew up in Ystradgynlais Huw David Richards is a former Welsh and Neath RFC rugby union player, he played in the 1987 Rugby World Cup, as a lock, became the first player to receive a red card in a Rugby World Cup tournament. Richards was born in Carmarthen and attended school in Ystradgynlais Kevin Hopkins a former Wales international rugby player was brought up in Ystradgynlais, attending Maesydderwen Comprehensive School, started his playing career with Ystradgynlais RFC, he too played for Wales in the 1987 Rugby World Cup. Prison reform campaigner Ben Gunn grew up in the town. Convicted of murder at the age of 14, he served 32 years in prison before being released on licence.
Grownups actor Steve Meo attended Maesydderwen Comprehensive School in the town. It i
Knighton is a small market town and community in central Powys, Wales, on the Teme and the Wales-England border. A small part of the town including Knighton railway station is in England; this Anglo-Saxon settlement became a Norman fortified town. The Welsh name, Tref-y-clawdd, meaning "town on the dyke", was first recorded in 1262 and given to the town in 1971; the name Knighton derives from the Old English words cniht and tūn meaning "... a soldier, personal follower, young man, thane, freeman" and "... farm, homestead". This implies that the settlement was founded as the result of a grant of land to freemen. Knighton's earliest history is obscure but there are local clues: Caer Caradoc is 2 miles away and just off the road towards Clun. Watling Street, a Roman road, passes a few miles to the east at Leintwardine. Any settlements around the Knighton area would have been part of the Iron Age kingdom of Cornovii which consisted of the modern-day counties as Cheshire, North Staffordshire, North Herefordshire, parts of Powys and Worcestershire.
Knighton is known for a well-preserved section of Offa's Dyke. Intriguingly, Wat's Dyke runs parallel to Offa's Dyke and a few miles to the east. An earthwork that runs north-south along the English/Welsh border from Basingwerk near Holywell to Oswestry; the dykes aside, two Norman castles, constructed in the 12th century, are the oldest survivors in modern Knighton. The town became a borough in 1203, with a charter permitting annual fair; the castle was besieged by Owain Glyndŵr in 1402 and the castle and much of the town were destroyed. The major battle of the rebellion was fought at Pilleth 3 miles south of the town in the same year; the town's church dates from the 11th century. It is one of only two in Wales dedicated to St Edward; this dedication to an English saint is a symptom of the dual English/Welsh nature of the town, not resolved until 1535 when Knighton was confirmed as part of Wales by the Acts of Union. Knighton has a Baptist chapel and a small Catholic church. Knighton first prospered as a centre of the wool trade in the 15th century and was an important point on the two drover routes from Montgomery to Hereford, from London to Aberystwyth.
Otherwise, Knighton was remote from the centres of commerce. It seemed that the railway revolution would fail to reach the town; the construction of the railway was made economically viable – just – by an entrepreneurial drive to connect the Mumbles and Milford Haven with the cities and factories of the industrial Midlands. The Knighton Railway Company was formed by local landowners and businessmen to build a line from Craven Arms to the town. Work began in August 1858 and the line reached Knighton in March 1861; the station itself was built in 1865. To mark the accession of H. M. Queen Elizabeth II in 1953 the initials "ER" were planted out in deciduous trees within an evergreen forest on the hill to the north of the town. In August 1970, Knighton hosted a rock festival with bands such as The Move and the somewhat more obscure Pete Brown & Piblokto, Roger Bunn, Forever More, Clark-Hutchinson, James Litherland's Brotherhood and Killing Floor. Comperes were radio DJ Pete Drummond and local resident and bluesman Alexis Korner, who performed.
After the Acts of Union, Knighton was for nearly 450 years part of the traditional County of Radnorshire. In common with many ancient counties Radnorshire ceased to exist in 1974 and was subsumed in the county of Powys; the town council of 13 councillors elects a ceremonial mayor annually. Real municipal authority lies with Powys County Council; the Knighton electoral ward was represented by two county councillors on Powys County Council, until 1999 when its representation was reduced to one. Knighton has been represented by the Liberal Democrats. Since May 2017 it has been represented by Independent councillor Ange Williams. Above the county council, the National Assembly for Wales forms the next tier of government. Knighton falls within the Westminster constituency of Brecon and Radnorshire and the current MP is Christopher Davies – a Conservative. Wales forms one large Wales European Parliamentary constituency, it is part of the National Assembly for Wales constituency of Brecon and Radnorshire and represented by Kirsty Williams AM.
The town returns a single councillor to Powys County Council. The few roads and houses that lie across the border in England are part of the civil parish of Stowe, in the county of Shropshire; this is part of the Westminster constituency of Ludlow and the current MP is Philip Dunne – a Conservative. It lies in the European Parliamentary Constituency of West Midlands. Knighton has a fire station served by a part-time crew and part of the Mid and West Wales Fire and Rescue Service. Knighton's police station is part-time. Knighton has a hospital on Ffrydd Road on the site of and using some of the former buildings of the workhouse, it has maternity facilities but no emergency capacity. Primary care is provided by a Boots pharmacy. Social housing is provided by two housing associations.
In hydrology, the inflow of a body of water is the source of the water in the body of water. It can refer to the average volume of incoming water in unit time, it is contrasted with outflow. All bodies of water have multiple inflows, but one inflow may predominate and be the largest source of water. However, in many cases, no single inflow will predominate and there will be multiple primary inflows. For a lake, the inflow may be a river or stream that flows into the lake. Inflow may be speaking, not flows, but rather precipitation, like rain. Inflow can be used to refer to groundwater recharge; the dictionary definition of inflow at Wiktionary