Yam (vegetable)
Yam is the common name for some plant species in the genus Dioscorea that form edible tubers. Yams are perennial herbaceous vines cultivated for the consumption of their starchy tubers in many temperate and tropical world regions; the tubers themselves are called "yams", having numerous cultivars and related species. In parts of the United States and Canada, "yam" is sometimes used to refer to varieties of the unrelated sweet potato; the name, appears to derive from Portuguese inhame or Canarian ñame, which derived from West African languages during trade. The main derivations borrow from verbs meaning "to eat". In various places other unrelated root vegetables are sometimes referred to as "yams", including: In the United States, the sweet potato those with orange flesh, are referred to as "yams" In Okinawa, purple sweet potatoes may be called "yams" In New Zealand, the oca is referred to as "yam" In Japan, konjac corms are colloquially referred to as "yams" In Malaysia and Singapore the taro is referred to as a "yam"Yam has various common names across multiple world regions.
A monocot related to lilies and grasses, yams are vigorous herbaceous vines, providing an edible tuber. They are native to Africa and the Americas; some yams are invasive plants considered a "noxious weed", outside cultivated areas. Yam tubers vary in size from that of a small potato to over 60 g; some 870 species of yams are known, 95% of these crops are grown in Africa. Yam tubers can grow up to 15 m in length and 7.6 to 15.2 cm high. The tuber may grow into the soil up to 1.5 metres deep. The plant disperses by seed; the edible tuber softens after heating. The skins vary in color from dark brown to light pink; the majority of the vegetable is composed of a much softer substance known as the "meat". This substance ranges in color from pink in mature yams. Yam crop begins when whole seed tubers or tuber portions are planted into mounds or ridges, at the beginning of the rainy season; the crop yield depends on how and where the sets are planted, sizes of mounds, interplant spacing, provision of stakes for the resultant plants, yam species, tuber sizes desired at harvest.
Small-scale farmers in West and Central Africa intercrop yams with cereals and vegetables. The seed yams are bulky to transport. Farmers who do not buy new seed yams set aside up to 30% of their harvest for planting the next year. Yam crops face pressure from a range of insect pests and fungal and viral diseases, as well as nematode, their growth and dormant phases correspond to the wet season and the dry season. For maximum yield, the yams require a humid tropical environment, with an annual rainfall over 1500 mm distributed uniformly throughout the growing season. White and water yams produce a single large tuber per year weighing 5 to 10 kg. Despite the high labor requirements and production costs, consumer demand for yam is high in certain subregions of Africa, making yam cultivation quite profitable to certain farmers. Many cultivars of yams are found throughout the humid tropics; the most economically important are discussed below. Dioscorea rotundata, the white yam, D. cayenensis, the yellow yam, are native to Africa.
They are the most important cultivated yams. In the past, they were considered as two separate species, but most taxonomists now regard them as the same species. Over 200 varieties between them are cultivated. White yam tuber is cylindrical in shape, the skin is smooth and brown, the flesh is white and firm. Yellow yam has yellow flesh, caused by the presence of carotenoids, it looks similar to the white yam in outer appearance. The yellow yam has a shorter dormancy than white yam. The'Kokoro' variety is important in making dried yam chips, they are large plants. The tubers most weigh about 2.5 to 5 kg each, but can weigh as much as 25 kg. After 7 to 12 months' growth, the tubers are harvested. In Africa, most are pounded into a paste to make the traditional dish of "pounded yam," known as Iyan. D. alata, called "white yam", winged yam, water yam, purple yam, was first cultivated in Southeast Asia. Although not grown in the same quantities as the African yams, it has the largest distribution worldwide of any cultivated yam, being grown in Asia, the Pacific islands and the West Indies.
In Africa, the popularity of water yam is second only to white yam. The tuber shape is cylindrical, but can vary. Tuber flesh is watery in texture. Uhi was brought to Hawaii by the early Polynesian settlers and became a major crop in the 19th century when the tubers were sold to visiting ships as an stored food supply for their voyages. D. polystachya, Chinese yam, is native to China. The Chinese yam plant is somewhat smaller with the vines about 3 m long, it can be grown in much cooler conditions than other yams. It is grown in Korea and Japan, it was introduced to Europe in the 19th century, when the potato crop there was falling victim to disease, is still grown in France for the Asian food market. The tubers are harvested after about 6 months of growth; some are eaten right after harvesting and some are used as ingredients for other dishes, including noodles, for traditional medicines. D. bulbifera, the air
Ogbomosho North
Ogbomosho North is a Local Government Area in Oyo State, Nigeria. Its headquarters is in Ogbomoso and headed by Chairman Oladeji A. Olanrewaju; the local government serves as a home to one of Nigeria's best institution of learning, Ladoke Akintola University of Technology and it teaching hospital. The Nigerian Baptist Medical Center and Bowen University Teaching hospital are situated there; the SOUN Palace is the major traditional home of the town. Ogbomoso North is the largest local government in the city, it is the most populous local government in the city as at the 2006 census. The postal code of the area is 201
Nigeria
Nigeria the Federal Republic of Nigeria, is a federal republic in West Africa, bordering Niger in the north, Chad in the northeast, Cameroon in the east, Benin in the west. Its coast in the south is located on the Gulf of Guinea in the Atlantic Ocean; the federation comprises 36 states and 1 Federal Capital Territory, where the capital, Abuja, is located. The constitution defines Nigeria as a democratic secular country. Nigeria has been home to states over the millennia; the modern state originated from British colonial rule beginning in the 19th century, took its present territorial shape with the merging of the Southern Nigeria Protectorate and Northern Nigeria Protectorate in 1914. The British set up administrative and legal structures while practising indirect rule through traditional chiefdoms. Nigeria became a formally independent federation in 1960, it experienced a civil war from 1967 to 1970. It thereafter alternated between democratically elected civilian governments and military dictatorships until it achieved a stable democracy in 1999, with the 2011 presidential election considered the first to be reasonably free and fair.
Nigeria is referred to as the "Giant of Africa", owing to its large population and economy. With 186 million inhabitants, Nigeria is the most populous country in Africa and the seventh most populous country in the world. Nigeria has the third-largest youth population in the world, after India and China, with more than 90 million of its population under age 18; the country is viewed as a multinational state as it is inhabited by 250 ethnic groups, of which the three largest are the Hausa and Yoruba. The official language is English. Nigeria is divided in half between Christians, who live in the southern part of the country, Muslims, who live in the north. A minority of the population practice religions indigenous to Nigeria, such as those native to the Igbo and Yoruba ethnicities; as of 2015, Nigeria is the world's 20th largest economy, worth more than $500 billion and $1 trillion in terms of nominal GDP and purchasing power parity respectively. It overtook South Africa to become Africa's largest economy in 2014.
The 2013 debt-to-GDP ratio was 11 percent. Nigeria is considered to be an emerging market by the World Bank. However, it has a "low" Human Development Index, ranking 152nd in the world. Nigeria is a member of the MINT group of countries, which are seen as the globe's next "BRIC-like" economies, it is listed among the "Next Eleven" economies set to become among the biggest in the world. Nigeria is a founding member of the African Union and a member of many other international organizations, including the United Nations, the Commonwealth of Nations and OPEC; the name Nigeria was taken from the Niger River running through the country. This name was coined in the late 19th century by British journalist Flora Shaw, who married Lord Lugard, a British colonial administrator; the origin of the name Niger, which applied only to the middle reaches of the Niger River, is uncertain. The word is an alteration of the Tuareg name egerew n-igerewen used by inhabitants along the middle reaches of the river around Timbuktu prior to 19th-century European colonialism.
The Nok civilisation of Northern Nigeria flourished between 500 BC and AD 200, producing life-sized terracotta figures that are some of the earliest known sculptures in Sub-Saharan Africa. Further north, the cities Kano and Katsina have a recorded history dating to around 999 AD. Hausa kingdoms and the Kanem–Bornu Empire prospered as trade posts between North and West Africa; the Kingdom of Nri of the Igbo people consolidated in the 10th century and continued until it lost its sovereignty to the British in 1911. Nri was ruled by the Eze Nri, the city of Nri is considered to be the foundation of Igbo culture. Nri and Aguleri, where the Igbo creation myth originates, are in the territory of the Umeuri clan. Members of the clan trace their lineages back to the patriarchal king-figure Eri. In West Africa, the oldest bronzes made using the lost-wax process were from Igbo-Ukwu, a city under Nri influence; the Yoruba kingdoms of Ife and Oyo in southwestern Nigeria became prominent in the 12th and 14th centuries, respectively.
The oldest signs of human settlement at Ife's current site date back to the 9th century, its material culture includes terracotta and bronze figures. Oyo, at its territorial zenith in the late 17th to early 18th centuries, extended its influence from western Nigeria to modern-day Togo; the Edo's Benin Empire is located in southwestern Nigeria. Benin's power lasted between the 19th centuries, their dominance reached further. At the beginning of the 19th century, Usman dan Fodio directed a successful jihad and created and led the centralised Fulani Empire; the territory controlled by the resultant state included much of modern-day northern and central Nigeria. For centuries, various peoples in modern-day Nigeria traded overland with traders from North Africa. Cities in the area became regional centres in a broad network of trade routes that spanned western and northern Africa. In the 16th century, Portuguese explorers were the first Europeans to begin significant, direct trade with peoples of modern-day Nigeria, at the port they named Lago
Textile
A textile is a flexible material consisting of a network of natural or artificial fibers. Yarn is produced by spinning raw fibres of wool, cotton, hemp, or other materials to produce long strands. Textiles are formed by weaving, crocheting, knotting or tatting, felting, or braiding; the related words "fabric" and "cloth" and "material" are used in textile assembly trades as synonyms for textile. However, there are subtle differences in these terms in specialized usage. A textile is any material made of interlacing fibres, including carpeting and geotextiles. A fabric is a material made through weaving, spreading, crocheting, or bonding that may be used in production of further goods. Cloth may be used synonymously with fabric but is a piece of fabric, processed; the word'textile' is from Latin, from the adjective textilis, meaning'woven', from textus, the past participle of the verb texere,'to weave'. The word'fabric' derives from Latin, most from the Middle French fabrique, or'building, thing made', earlier as the Latin fabrica'workshop.
The word'cloth' derives from the Old English clað, meaning a cloth, woven or felted material to wrap around one, from Proto-Germanic kalithaz. The first clothes, worn at least 70,000 years ago and much earlier, were made of animal skins and helped protect early humans from the ice ages. At some point people learned to weave plant fibers into textiles; the discovery of dyed flax fibres in a cave in the Republic of Georgia dated to 34,000 BCE suggests textile-like materials were made in prehistoric times. The production of textiles is a craft whose speed and scale of production has been altered beyond recognition by industrialization and the introduction of modern manufacturing techniques. However, for the main types of textiles, plain weave, twill, or satin weave, there is little difference between the ancient and modern methods. Textiles have an assortment of uses, the most common of which are for clothing and for containers such as bags and baskets. In the household they are used in carpeting, upholstered furnishings, window shades, coverings for tables and other flat surfaces, in art.
In the workplace they are used in scientific processes such as filtering. Miscellaneous uses include flags, tents, handkerchiefs, cleaning rags, transportation devices such as balloons, kites and parachutes. Textiles are used in many traditional crafts such as sewing and embroidery. Textiles for industrial purposes, chosen for characteristics other than their appearance, are referred to as technical textiles. Technical textiles include textile structures for automotive applications, medical textiles, agrotextiles, protective clothing. In all these applications stringent performance requirements must be met. Woven of threads coated with zinc oxide nanowires, laboratory fabric has been shown capable of "self-powering nanosystems" using vibrations created by everyday actions like wind or body movements. Textiles are made from many materials, with four main sources: animal, plant and synthetic; the first three are natural. In the 20th century, they were supplemented by artificial fibres made from petroleum.
Textiles are made in various strengths and degrees of durability, from the finest microfibre made of strands thinner than one denier to the sturdiest canvas. Textile manufacturing terminology has a wealth of descriptive terms, from light gauze-like gossamer to heavy grosgrain cloth and beyond. Animal textiles are made from hair, skin or silk. Wool refers to the hair of the domestic sheep or goat, distinguished from other types of animal hair in that the individual strands are coated with scales and crimped, the wool as a whole is coated with a wax mixture known as lanolin, waterproof and dirtproof. Woollen refers to a bulkier yarn produced from carded, non-parallel fibre, while worsted refers to a finer yarn spun from longer fibres which have been combed to be parallel. Wool is used for warm clothing. Cashmere, the hair of the Indian cashmere goat, mohair, the hair of the North African angora goat, are types of wool known for their softness. Other animal textiles which are made from hair or fur are alpaca wool, vicuña wool, llama wool, camel hair used in the production of coats, ponchos and other warm coverings.
Angora refers to the long, soft hair of the angora rabbit. Qiviut is the fine inner wool of the muskox. Wadmal is a coarse cloth made of wool, produced in Scandinavia 1000~1500 CE. Sea silk is an fine and valuable fabric, made from the silky filaments or byssus secreted by a gland in the foot of pen shells. Silk is an animal textile made from the fibres of the cocoon of the Chinese silkworm, spun into a smooth fabric prized for its softness. There are two main ty
Agriculture
Agriculture is the science and art of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to live in cities; the history of agriculture began thousands of years ago. After gathering wild grains beginning at least 105,000 years ago, nascent farmers began to plant them around 11,500 years ago. Pigs and cattle were domesticated over 10,000 years ago. Plants were independently cultivated in at least 11 regions of the world. Industrial agriculture based on large-scale monoculture in the twentieth century came to dominate agricultural output, though about 2 billion people still depended on subsistence agriculture into the twenty-first. Modern agronomy, plant breeding, agrochemicals such as pesticides and fertilizers, technological developments have increased yields, while causing widespread ecological and environmental damage. Selective breeding and modern practices in animal husbandry have increased the output of meat, but have raised concerns about animal welfare and environmental damage.
Environmental issues include contributions to global warming, depletion of aquifers, antibiotic resistance, growth hormones in industrial meat production. Genetically modified organisms are used, although some are banned in certain countries; the major agricultural products can be broadly grouped into foods, fibers and raw materials. Food classes include cereals, fruits, meat, milk and eggs. Over one-third of the world's workers are employed in agriculture, second only to the service sector, although the number of agricultural workers in developed countries has decreased over the centuries; the word agriculture is a late Middle English adaptation of Latin agricultūra, from ager, "field", which in its turn came from Greek αγρός, cultūra, "cultivation" or "growing". While agriculture refers to human activities, certain species of ant and ambrosia beetle cultivate crops. Agriculture is defined with varying scopes, in its broadest sense using natural resources to "produce commodities which maintain life, including food, forest products, horticultural crops, their related services".
Thus defined, it includes arable farming, animal husbandry and forestry, but horticulture and forestry are in practice excluded. The development of agriculture enabled the human population to grow many times larger than could be sustained by hunting and gathering. Agriculture began independently in different parts of the globe, included a diverse range of taxa, in at least 11 separate centres of origin. Wild grains were eaten from at least 105,000 years ago. From around 11,500 years ago, the eight Neolithic founder crops and einkorn wheat, hulled barley, lentils, bitter vetch, chick peas and flax were cultivated in the Levant. Rice was domesticated in China between 11,500 and 6,200 BC with the earliest known cultivation from 5,700 BC, followed by mung and azuki beans. Sheep were domesticated in Mesopotamia between 11,000 years ago. Cattle were domesticated from the wild aurochs in the areas of modern Turkey and Pakistan some 10,500 years ago. Pig production emerged in Eurasia, including Europe, East Asia and Southwest Asia, where wild boar were first domesticated about 10,500 years ago.
In the Andes of South America, the potato was domesticated between 10,000 and 7,000 years ago, along with beans, llamas and guinea pigs. Sugarcane and some root vegetables were domesticated in New Guinea around 9,000 years ago. Sorghum was domesticated in the Sahel region of Africa by 7,000 years ago. Cotton was domesticated in Peru by 5,600 years ago, was independently domesticated in Eurasia. In Mesoamerica, wild teosinte was bred into maize by 6,000 years ago. Scholars have offered multiple hypotheses to explain the historical origins of agriculture. Studies of the transition from hunter-gatherer to agricultural societies indicate an initial period of intensification and increasing sedentism. Wild stands, harvested started to be planted, came to be domesticated. In Eurasia, the Sumerians started to live in villages from about 8,000 BC, relying on the Tigris and Euphrates rivers and a canal system for irrigation. Ploughs appear in pictographs around 3,000 BC. Farmers grew wheat, vegetables such as lentils and onions, fruits including dates and figs.
Ancient Egyptian agriculture relied on its seasonal flooding. Farming started in the predynastic period at the end of the Paleolithic, after 10,000 BC. Staple food crops were grains such as wheat and barley, alongside industrial crops such as flax and papyrus. In India, wheat and jujube were domesticated by 9,000 BC, soon followed by sheep and goats. Cattle and goats were domesticated in Mehrgarh culture by 8,000–6,000 BC. Cotton was cultivated by the 5th-4th millennium BC. Archeological evidence indicates an animal-drawn plough from 2,500 BC in the Indus Valley Civilisation. In China, from the 5th century BC there was a nationwide granary system and widespread silk farming. Water-powered grain mills were in use followed by irrigation. By the late 2nd century, heavy ploughs had been developed with iron mouldboards; these spread westwards across Eurasia. Asian rice was domesticated 8,200–13,500 years ago – depending on the molecular clock estimate, used – on the Pearl River in southern China with a single genetic origin from the wild rice Oryza rufipogon
Cassava
Manihot esculenta called cassava, yuca, mandioca and Brazilian arrowroot, is a woody shrub native to South America of the spurge family, Euphorbiaceae. It is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates. Though it is called yuca in Spanish and in the United States, it is not related to yucca, a shrub in the family Asparagaceae. Cassava, when dried to a powdery extract, is called tapioca. Cassava is the third-largest source of food carbohydrates in the tropics, after maize. Cassava is a major staple food in the developing world, providing a basic diet for over half a billion people, it is one of the most drought-tolerant crops, capable of growing on marginal soils. Nigeria is the world's largest producer of cassava, while Thailand is the largest exporter of dried cassava. Cassava is classified as either bitter. Like other roots and tubers, both bitter and sweet varieties of cassava contain antinutritional factors and toxins, with the bitter varieties containing much larger amounts.
It must be properly prepared before consumption, as improper preparation of cassava can leave enough residual cyanide to cause acute cyanide intoxication and ataxia, partial paralysis, or death. The more toxic varieties of cassava are a fall-back resource in times of famine or food insecurity in some places. Farmers prefer the bitter varieties because they deter pests and thieves; the cassava root is long and tapered, with a firm, homogeneous flesh encased in a detachable rind, about 1 mm thick and brown on the outside. Commercial cultivars can be 5 to 10 cm in diameter at the top, around 15 to 30 cm long. A woody vascular bundle runs along the root's axis; the flesh can be yellowish. Cassava roots are rich in starch and contain small amounts of calcium and vitamin C. However, they are poor in protein and other nutrients. In contrast, cassava leaves are a good source of protein, but deficient in the amino acid methionine and tryptophan. Wild populations of M. esculenta subspecies flabellifolia, shown to be the progenitor of domesticated cassava, are centered in west-central Brazil, where it was first domesticated no more than 10,000 years BP.
Forms of the modern domesticated species can be found growing in the wild in the south of Brazil. By 4,600 BC, manioc pollen appears in the Gulf of Mexico lowlands, at the San Andrés archaeological site; the oldest direct evidence of cassava cultivation comes from a 1,400-year-old Maya site, Joya de Cerén, in El Salvador. With its high food potential, it had become a staple food of the native populations of northern South America, southern Mesoamerica, the Caribbean by the time of European contact in 1492. Cassava was a staple food of pre-Columbian peoples in the Americas and is portrayed in indigenous art; the Moche people depicted yuca in their ceramics. Spaniards in their early occupation of Caribbean islands did not want to eat cassava or maize, which they considered insubstantial and not nutritious, they much preferred foods from Spain wheat bread, olive oil, red wine, meat, considered maize and cassava damaging to Europeans. For these Christians in the New World, cassava was not suitable for communion since it could not undergo transubstantiation and become the body of Christ.
"Wheat flour was the symbol of Christianity itself" and colonial-era catechisms stated explicitly that only wheat flour could be used. The cultivation and consumption of cassava was nonetheless continued in both Portuguese and Spanish America. Mass production of cassava bread became the first Cuban industry established by the Spanish, Ships departing to Europe from Cuban ports such as Havana, Santiago and Baracoa carried goods to Spain, but sailors needed to be provisioned for the voyage; the Spanish needed to replenish their boats with dried meat, water and large amounts of cassava bread. Sailors complained. Tropical Cuban weather was not suitable for wheat planting and cassava would not go stale as as regular bread. Cassava was introduced to Africa by Portuguese traders from Brazil in the 16th century. Around the same period, it was introduced to Asia through Columbian Exchange by Portuguese and Spanish traders, planted in their colonies in Goa, Eastern Indonesia and the Philippines. Maize and cassava are now important staple foods.
Cassava has become an important staple in Asia, extensively cultivated in Indonesia and Vietnam. Cassava is sometimes described as the "bread of the tropics" but should not be confused with the tropical and equatorial bread tree, the breadfruit or the African breadfruit. In 2016, global production of cassava root was 277 million tonnes, with Nigeria as the world's largest producer having 21% of the world total. Other major growers were Thailand and Indonesia. Cassava is one of the most drought-tolerant crops, can be grown on marginal soils, gives reasonable yields where many other crops do not grow well. Cassava is well adapted within latitudes 30° north and south of the equator, at elevations between sea level and 2,000 m above sea level, in equatorial temperatures, with rainfalls from 50 mm to 5 m annually, to poor soils with a pH ranging from acidic to alkaline; these conditions are common in certain parts of Africa and So
Dam
A dam is a barrier that stops or restricts the flow of water or underground streams. Reservoirs created by dams not only suppress floods but provide water for activities such as irrigation, human consumption, industrial use and navigability. Hydropower is used in conjunction with dams to generate electricity. A dam can be used to collect water or for storage of water which can be evenly distributed between locations. Dams serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions; the earliest known dam is the Jawa Dam in Jordan, dating to 3,000 BC. The word dam can be traced back to Middle English, before that, from Middle Dutch, as seen in the names of many old cities; the first known appearance of dam occurs in 1165. However, there is one village, mentioned in 1120; the word seems to be related to the Greek word taphos, meaning "grave" or "grave hill". So the word should be understood as "dike from dug out earth".
The names of more than 40 places from the Middle Dutch era such as Amsterdam and Rotterdam bear testimony to the use of the word in Middle Dutch at that time. Early dam building took place in the Middle East. Dams were used to control the water level, for Mesopotamia's weather affected the Tigris and Euphrates rivers; the earliest known dam is the Jawa Dam in Jordan, 100 kilometres northeast of the capital Amman. This gravity dam featured an 9-metre-high and 1 m-wide stone wall, supported by a 50 m-wide earth rampart; the structure is dated to 3000 BC. The Ancient Egyptian Sadd-el-Kafara Dam at Wadi Al-Garawi, located about 25 km south of Cairo, was 102 m long at its base and 87 m wide; the structure was built around 2800 or 2600 BC as a diversion dam for flood control, but was destroyed by heavy rain during construction or shortly afterwards. During the Twelfth Dynasty in the 19th century BC, the Pharaohs Senosert III, Amenemhat III and Amenemhat IV dug a canal 16 km long linking the Fayum Depression to the Nile in Middle Egypt.
Two dams called Ha-Uar running east-west were built to retain water during the annual flood and release it to surrounding lands. The lake called "Mer-wer" or Lake Moeris is known today as Birket Qarun. By the mid-late third millennium BC, an intricate water-management system within Dholavira in modern-day India was built; the system included 16 reservoirs and various channels for collecting water and storing it. One of the engineering wonders of the ancient world was the Great Dam of Marib in Yemen. Initiated somewhere between 1750 and 1700 BC, it was made of packed earth – triangular in cross section, 580 m in length and 4 m high – running between two groups of rocks on either side, to which it was linked by substantial stonework. Repairs were carried out during various periods, most important around 750 BC, 250 years the dam height was increased to 7 m. After the end of the Kingdom of Saba, the dam fell under the control of the Ḥimyarites who undertook further improvements, creating a structure 14 m high, with five spillway channels, two masonry-reinforced sluices, a settling pond, a 1,000 m canal to a distribution tank.
These extensive works were not finalized until 325 AD and allowed the irrigation of 25,000 acres. Eflatun Pınar is a Hittite spring temple near Konya, Turkey, it is thought to be from the time of the Hittite empire between the 15th and 13th century BC. The Kallanai is constructed of unhewn stone, over 300 m long, 4.5 m high and 20 m wide, across the main stream of the Kaveri river in Tamil Nadu, South India. The basic structure dates to the 2nd century AD and is considered one of the oldest water-diversion or water-regulator structures in the world, still in use; the purpose of the dam was to divert the waters of the Kaveri across the fertile delta region for irrigation via canals. Du Jiang Yan is the oldest surviving irrigation system in China that included a dam that directed waterflow, it was finished in 251 BC. A large earthen dam, made by Sunshu Ao, the prime minister of Chu, flooded a valley in modern-day northern Anhui province that created an enormous irrigation reservoir, a reservoir, still present today.
Roman dam construction was characterized by "the Romans' ability to plan and organize engineering construction on a grand scale." Roman planners introduced the then-novel concept of large reservoir dams which could secure a permanent water supply for urban settlements over the dry season. Their pioneering use of water-proof hydraulic mortar and Roman concrete allowed for much larger dam structures than built, such as the Lake Homs Dam the largest water barrier to that date, the Harbaqa Dam, both in Roman Syria; the highest Roman dam was the Subiaco Dam near Rome. Roman engineers made routine use of ancient standard designs like embankment dams and masonry gravity dams. Apart from that, they displayed a high degree of inventiveness, introducing most of the other basic dam designs, unknown until then; these include arch-gravity dams, arch dams, buttress dams and multiple arch buttress dams, all of which were known and employed by the 2nd century AD. Roman workforces were the first to build dam bridges, such as the Bridge of Valerian in Iran
Nigeria
