A hunter-gatherer is a human living in a society in which most or all food is obtained by foraging. Hunter-gatherer societies stand in contrast to agricultural societies, which rely on domesticated species. Hunting and gathering was humanity's first and most successful adaptation, occupying at least 90 percent of human history. Following the invention of agriculture, hunter-gatherers who did not change have been displaced or conquered by farming or pastoralist groups in most parts of the world. In West Eurasia, agriculture lead to widespread genetic changes when older hunter-gatherer populations were replaced by Middle Eastern farmers during the Neolithic who in turn were overrun by Indo-Europeans during the Bronze Age. Only a few contemporary societies are classified as hunter-gatherers, many supplement their foraging activity with horticulture or pastoralism. During the 1970s, Lewis Binford suggested that early humans were obtaining food via scavenging, not hunting. Early humans in the Lower Paleolithic lived in forests and woodlands, which allowed them to collect seafood, eggs and fruits besides scavenging.
Rather than killing large animals for meat, according to this view, they used carcasses of such animals that had either been killed by predators or that had died of natural causes. Archaeological and genetic data suggest that the source populations of Paleolithic hunter-gatherers survived in sparsely wooded areas and dispersed through areas of high primary productivity while avoiding dense forest cover. According to the endurance running hypothesis, long-distance running as in persistence hunting, a method still practiced by some hunter-gatherer groups in modern times, was the driving evolutionary force leading to the evolution of certain human characteristics; this hypothesis does not contradict the scavenging hypothesis: both subsistence strategies could have been in use – sequentially, alternating or simultaneously. Hunting and gathering was the subsistence strategy employed by human societies beginning some 1.8 million years ago, by Homo erectus, from its appearance some 0.2 million years ago by Homo sapiens.
Prehistoric hunter-gatherers lived in groups that consisted of several families resulting in a size of a few dozen people. It remained the only mode of subsistence until the end of the Mesolithic period some 10,000 years ago, after this was replaced only with the spread of the Neolithic Revolution. Starting at the transition between the Middle to Upper Paleolithic period, some 80,000 to 70,000 years ago, some hunter-gatherers bands began to specialize, concentrating on hunting a smaller selection of game and gathering a smaller selection of food; this specialization of work involved creating specialized tools such as fishing nets and bone harpoons. The transition into the subsequent Neolithic period is chiefly defined by the unprecedented development of nascent agricultural practices. Agriculture originated as early as 12,000 years ago in the Middle East, independently originated in many other areas including Southeast Asia, parts of Africa and the Andes. Forest gardening was being used as a food production system in various parts of the world over this period.
Forest gardens originated in prehistoric times along jungle-clad river banks and in the wet foothills of monsoon regions. In the gradual process of families improving their immediate environment, useful tree and vine species were identified and improved, whilst undesirable species were eliminated. Superior introduced species were selected and incorporated into the gardens. Many groups continued their hunter-gatherer ways of life, although their numbers have continually declined as a result of pressure from growing agricultural and pastoral communities. Many of them reside in arid regions or tropical forests. Areas that were available to hunter-gatherers were—and continue to be—encroached upon by the settlements of agriculturalists. In the resulting competition for land use, hunter-gatherer societies either adopted these practices or moved to other areas. In addition, Jared Diamond has blamed a decline in the availability of wild foods animal resources. In North and South America, for example, most large mammal species had gone extinct by the end of the Pleistocene—according to Diamond, because of overexploitation by humans, one of several explanations offered for the Quaternary extinction event there.
As the number and size of agricultural societies increased, they expanded into lands traditionally used by hunter-gatherers. This process of agriculture-driven expansion led to the development of the first forms of government in agricultural centers, such as the Fertile Crescent, Ancient India, Ancient China, Sub-Saharan Africa and Norte Chico; as a result of the now near-universal human reliance upon agriculture, the few contemporary hunter-gatherer cultures live in areas unsuitable for agricultural use. Archaeologists can use evidence such as stone tool use to track hunter-gatherer activities, including mobility. Most hunter-gatherers are semi-nomadic and live in temporary settlements. Mobile communities construct shelters using impermanent building materials, or they may use natural rock shelters, where they are available; some hunter-gatherer cultures, such as the indigenous peoples of the Pacific Northwest Coast and the Yakuts, lived in rich environments that allowed them to be sedentary or semi-sedentary.
Hunter-gatherers tend to have an egalitarian social ethos, although settled hunter-gatherers are an exception to this rule. Nearly
The Tabqa Dam, or al-Thawra Dam as it is named, most known as Euphrates Dam, is an earthen dam on the Euphrates, located 40 kilometres upstream from the city of Raqqa in Raqqa Governorate, Syria. The city of Al-Thawrah is located south of the dam; the dam is 60 metres high and 4.5 kilometres long and is the largest dam in Syria. Its construction led to the creation of Syria's largest water reservoir; the dam was constructed between 1973 with help from the Soviet Union. At the same time, an international effort was made to excavate and document as many archaeological remains as possible in the area of the future lake before they would be flooded by the rising water; when the flow of the Euphrates was reduced in 1974 to fill the lake behind the dam, a dispute broke out between Syria and Iraq, settled by intervention from Saudi Arabia and the Soviet Union. The dam was built to generate hydroelectric power, as well as irrigate lands on both sides of the Euphrates; the dam has not reached its full potential in either of these objectives.
In 1927, when Syria was a French mandate, it was proposed to build a dam in the Euphrates near the Syro–Turkish border. After Syria became independent in 1946, the feasibility of this proposal was re-investigated, but the plan was not carried out. In 1957, the Syrian government reached an agreement with the Soviet Union for technical and financial aid for the construction of a dam in the Euphrates. Syria, as part of the United Arab Republic, signed an agreement with West Germany in 1960 for a loan to finance the construction of the dam. After Syria left the UAR in 1961, a new agreement about the financing of the dam was reached with the Soviet Union in 1965. A special government department was created in 1961 to oversee the construction of the dam. In the early 1960s Swedish geomorphologist Åke Sundborg worked as advisor in the dam project with the task of estimating the amount and fate of sediments that would enter into the dam. Sundborg developed for this purpose a mathematical model on the prognosed growth of a river delta in the dam.
The Tabqa Dam was conceived as a dual-purpose dam. The dam would include a hydroelectric power station with eight turbines capable of producing 824 MW in total, would irrigate an area of 640,000 hectares on both sides of the Euphrates. Construction of the dam lasted between 1968 and 1973, while the accompanying power station was finished on 8 March 1978; the dam was constructed during the agricultural reform policies of Hafez al-Assad, who had re-routed the Euphrates river for the dam in 1974. Total cost of the dam was US$340 million of which US$100 million was in the form of a loan by the Soviet Union; the Soviet Union provided technical expertise. During construction, up to 12 thousand Syrians and 900 Russian technicians worked on the dam, they were housed in the expanded town near the construction site, subsequently renamed Al-Thawra. To facilitate this project, as well as the construction of irrigation works on the Khabur River, the national railway system was extended from Aleppo to the dam, Deir ez-Zor, Qamishli.
The four thousand-some Arab families, living in the flooded part of the Euphrates Valley were resettled in other parts of northern Syria. This resettlement was part of an only implemented plan to establish an "Arab belt" along the borders with Turkey and Iraq in order to separate Kurds living in Syria from Kurds living in Turkey and Iraq. In 1974, Syria started to fill the lake behind the dam by reducing the flow of the Euphrates. Earlier, Turkey had started filling the reservoir of the newly constructed Keban Dam, at the same time the area was hit by significant drought; as a result, Iraq received less water from the Euphrates than normal, complained that annual Euphrates flow had dropped from 15.3 cubic kilometres in 1973 to 9.4 cubic kilometres in 1975. Iraq asked the Arab League to intervene but Syria argued that it received less water from Turkey as well and refused to cooperate; as a result, tensions rose and Iraq and Syria sent troops to their shared border. Iraq threatened to bomb the Tabqa Dam.
Before the dispute could escalate any further, an agreement was reached in 1975 by mediation of Saudi Arabia and the Soviet Union whereby Syria increased the flow from the dam and henceforth agreed to let 60 percent of the Euphrates water flow into Iraq. In 1987, Turkey and Iraq signed an agreement by which Turkey was committed to maintain an average Euphrates flow of 500 cubic metres per second into Syria, which translates into 16 cubic kilometres of water per year; the upper part of the Syrian Euphrates valley has been intensively occupied at least since the Late Natufian period. Nineteenth- and early twentieth-century European travellers had noted the presence of numerous archaeological sites in the area that would be flooded by the new reservoir. In order to preserve or at least document as many of these remains as possible, an extensive archaeological rescue programme was initiated during which more than 25 sites were excavated. Between 1963 and 1965, archaeological sites and remains were located with the help of aerial photographs, a ground survey was carried out as well to determine the periods that were present at each site.
Between 1965 a
In archaeology, a tell, or tel, is an artificial mound formed from the accumulated refuse of generations of people living on the same site for hundreds or thousands of years. A classic can be up to 30 metres high. Tells are most associated with the archaeology of the ancient Near East, but they are found elsewhere, such as Central Asia, Eastern Europe, West Africa and Greece. Within the Near East, they are concentrated in less arid regions, including Upper Mesopotamia, the Southern Levant and Iran, which had more continuous settlement. A tell is an artificial hill created by many generations of people living and rebuilding on the same spot. Over time, the level rises; the single biggest contributor to the mass of a tell are mud bricks. Excavating a tell can reveal buried structures such as government or military buildings, religious shrines, homes, located at different depths depending on their date of use, they overlap horizontally, vertically, or both. Archaeologists excavate tell sites to interpret architecture and date of occupation.
List of tells Archaeological site Tells portal Lloyd, Seton. Mounds of the Near East. Edinburgh: Edinburgh University Press – via Internet Archive
Rye is a grass grown extensively as a grain, a cover crop and a forage crop. It is a member of the wheat tribe and is related to barley and wheat. Rye grain is used for flour, beer, crisp bread, some whiskeys, some vodkas, animal fodder, it can be eaten whole, either as boiled rye berries or by being rolled, similar to rolled oats. Rye is a cereal grain and should not be confused with ryegrass, used for lawns and hay for livestock. Rye is one of a number of species that grow wild in central and eastern Turkey and in adjacent areas. Domesticated rye occurs in small quantities at a number of Neolithic sites in Turkey, such as the Pre-Pottery Neolithic B Can Hasan III near Çatalhöyük, but is otherwise absent from the archaeological record until the Bronze Age of central Europe, c. 1800–1500 BCE. It is possible that rye traveled west from Turkey as a minor admixture in wheat, was only cultivated in its own right. Although archeological evidence of this grain has been found in Roman contexts along the Rhine, in Ireland and Britain, Pliny the Elder was dismissive of rye, writing that it "is a poor food and only serves to avert starvation" and spelt is mixed into it "to mitigate its bitter taste, then is most unpleasant to the stomach".
Since the Middle Ages people have cultivated rye in Central and Eastern Europe. It serves as the main bread cereal in most areas east of the French-German border and north of Hungary. In Southern Europe, it was cultivated on marginal lands. Claims of much earlier cultivation of rye, at the Epipalaeolithic site of Tell Abu Hureyra in the Euphrates valley of northern Syria remain controversial. Critics point to inconsistencies in the radiocarbon dates, identifications based on grain, rather than on chaff. Winter rye is any breed of rye planted in the fall to provide ground cover for the winter, it grows during warmer days of the winter when sunlight temporarily warms the plant above freezing while there is general snow cover. It can be used to prevent the growth of winter-hardy weeds, can either be harvested as a bonus crop or tilled directly into the ground in spring to provide more organic matter for the next summer's crop, it is a common nurse crop. The nematode Ditylenchus dipsaci, leaf beetle, fruit fly, gout fly, cereal chafer, dart moth, cereal bug, Hessian fly, rustic shoulder knot are among insects which can affect rye health.
Rye is grown in Eastern and Northern Europe. The main rye belt stretches from northern Germany through Poland, Belarus and Latvia into central and northern Russia. Rye is grown in North America, in South America, in Oceania, in Turkey, in Kazakhstan and in northern China. Production levels of rye have fallen in most of the producing nations, as of 2012. For instance, production of rye in Russia fell from 13.9 million metric tons in 1992 to 2.1 t in 2012. Corresponding figures for other countries are as follows: Poland – falling from 5.9 t in 1992 to 2.9 t in 2005. Most rye is consumed locally or exported only to neighboring countries, rather than being shipped worldwide. World trade of rye is low compared with other grains such as wheat; the total export of rye for 2016 was $186M compared with $30.1B for wheat. Poland consumes the most rye per person at 32.4 kg/capita. Nordic and Baltic countries are very high; the EU in general is around 5.6 kg/capita. The entire world only consumes 0.9 kg/capita.
Rye is susceptible to the ergot fungus. Consumption of ergot-infected rye by humans and animals results in a serious medical condition known as ergotism. Ergotism can cause both physical and mental harm, including convulsions, necrosis of digits and death. Damp northern countries that have depended on rye as a staple crop were subject to periodic epidemics of this condition; such epidemics have been found to correlate with periods of frequent witch trials, such as the Salem witch trials in Massachusetts in 1692. Modern grain-cleaning and milling methods have eliminated the disease, but contaminated flour may end up in bread and other food products if the ergot is not removed before milling. Rye grain is refined into a flour. Rye flour is low in glutenin, it therefore has a lower gluten content than wheat flour. It contains a higher proportion of soluble fiber. Alkylresorcinols are phenolic lipids present in high amounts in the bran layer of rye. Rye bread, including pumpernickel, is made using rye flour and is a eaten food in Northern and Eastern Europe.
Rye is used to make crisp bread. Rye grain is used to make like rye whiskey and rye beer. Other uses of rye grain include an herbal medicine known as rye extract. Rye straw is used as livestock bedding, as a cover crop and green manure for soil amendment, to make crafts such as corn dollies. Physical properties of rye affect attributes of the final food product such as seed size and surface area, porosity; the surface area of the seed directly correlates to the heat transfer time. Smaller seeds have increased heat transfer. Seeds with lower amounts of porosity have lower tendencies to lose water during the process of drying. Rye grows well in much poorer soils than those necessary for most cereal grains. Thus, it is an especially
The almond is a species of tree native to Mediterranean climate regions of the Middle East, but cultivated elsewhere. The almond is the name of the edible and cultivated seed of this tree. Within the genus Prunus, it is classified with the peach in the subgenus Amygdalus, distinguished from the other subgenera by corrugations on the shell surrounding the seed; the fruit of the almond is a drupe, consisting of an outer hull and a hard shell with the seed, not a true nut, inside. Shelling almonds refers to removing the shell to reveal the seed. Almonds are sold unshelled. Blanched almonds are shelled almonds that have been treated with hot water to soften the seedcoat, removed to reveal the white embryo; the almond is a deciduous tree. The young twigs are green at first, becoming purplish where exposed to sunlight grey in their second year; the leaves are 8 -- 13 cm long, with a 2.5 cm petiole. The flowers are white to pale pink, 3–5 cm diameter with five petals, produced singly or in pairs and appearing before the leaves in early spring.
Almond grows best in Mediterranean climates with mild, wet winters. The optimal temperature for their growth is between 15 and 30 °C and the tree buds have a chilling requirement of 300 to 600 hours below 7.2 °C to break dormancy. Almonds begin bearing an economic crop in the third year after planting. Trees reach full bearing five to six years after planting; the fruit matures in 7 -- 8 months after flowering. The almond fruit is 3.5–6 cm long. In botanical terms, it is not a nut but a drupe; the outer covering or exocarp, fleshy in other members of Prunus such as the plum and cherry, is instead a thick, grey-green coat, called the hull. Inside the hull is a reticulated, woody shell called the endocarp. Inside the shell is the edible seed called a nut. One seed is present, but two occur. After the fruit matures, the hull splits and separates from the shell, an abscission layer forms between the stem and the fruit so that the fruit can fall from the tree; the almond is native to the Mediterranean climate region of the Middle East, from Syria, Turkey and eastward to Pakistan.
It was spread by humans in ancient times along the shores of the Mediterranean into northern Africa and southern Europe, more transported to other parts of the world, notably California, United States. The wild form of domesticated almond grows in parts of the Levant. Selection of the sweet type from the many bitter types in the wild marked the beginning of almond domestication, it is unclear as to. The species Prunus fenzliana may be the most wild ancestor of the almond in part because it is native of Armenia and western Azerbaijan where it was domesticated. Wild almond species were grown by early farmers, "at first unintentionally in the garbage heaps, intentionally in their orchards". Almonds were one of the earliest domesticated fruit trees due to "the ability of the grower to raise attractive almonds from seed. Thus, in spite of the fact that this plant does not lend itself to propagation from suckers or from cuttings, it could have been domesticated before the introduction of grafting".
Domesticated almonds appear in the Early Bronze Age such as the archaeological sites of Numeria, or earlier. Another well-known archaeological example of the almond is the fruit found in Tutankhamun's tomb in Egypt imported from the Levant. Of the European countries that the Royal Botanic Garden Edinburgh reported as cultivating almonds, Germany is the northernmost, though the domesticated form can be found as far north as Iceland; the word "almond" comes from Old French almande or alemande, Late Latin *amandula, derived through a form amygdala from the Greek ἀμυγδάλη, an almond. The al- in English, for the a- used in other languages may be due a confusion with the Arabic article al, the word having first dropped the a- as in the Italian form mandorla. Other related names of almond include mandel or knackmandel, mandorla, amêndoa, almendra; the adjective "amygdaloid" is used to describe objects which are almond-shaped a shape, part way between a triangle and an ellipse. See, for example, the brain structure amygdala, which uses a direct borrowing of the Greek term amygdalē.
The pollination of California's almonds is the largest annual managed pollination event in the world, with close to one million hives being trucked in February to the almond groves. Much of the pollination is managed by pollination brokers, who contract with migratory beekeepers from at least 49 states for the event; this business has been affected by colony collapse disorder, causing nationwide shortages of honey bees and increasing the price of insect pollination. To protect almond growers from the rising cost of insect pollination, researchers at the Agricultural Research Service have developed a new line of self-pollinating almond trees. Self-pollinating almond trees, such as the'Tuono', have been around
Accelerator mass spectrometry
Accelerator mass spectrometry is a form of mass spectrometry that accelerates ions to extraordinarily high kinetic energies before mass analysis. The special strength of AMS among the mass spectrometric methods is its power to separate a rare isotope from an abundant neighboring mass; the method suppresses molecular isobars and in many cases can separate atomic isobars also. This makes possible the detection of occurring, long-lived radio-isotopes such as 10Be, 36Cl, 26Al and 14C, their typical isotopic abundance ranges from 10−12 to 10−18. AMS can outperform the competing technique of decay counting for all isotopes where the half-life is long enough. Negative ions are created in an ion source. In fortunate cases this allows the suppression of an unwanted isobar, which does not form negative ions; the pre-accelerated ions are separated by a first mass spectrometer of sector-field type and enter an electrostatic "tandem accelerator". This is a large nuclear particle accelerator based on the principle of a Tandem van de Graaff Accelerator operating at 0.2 to many million volts with two stages operating in tandem to accelerate the particles.
At the connecting point between the two stages, the ions change charge from negative to positive by passing through a thin layer of matter. Molecules will break apart in this stripping stage; the complete suppression of molecular isobars is one reason for the exceptional abundance sensitivity of AMS. Additionally, the impact strips off several of the ion's electrons, converting it into a positively charged ion. In the second half of the accelerator, the now positively charged ion is accelerated away from the positive centre of the electrostatic accelerator which attracted the negative ion; when the ions leave the accelerator they are positively charged and are moving at several percent of the speed of light. In a second stage of mass spectrometer, the fragments from the molecules are separated from the ions of interest; this spectrometer may consist of magnetic or electric sectors, so-called velocity selectors, which utilizes both electric fields and magnetic fields. After this stage, no background is left, unless a stable isobar forming negative ions exists, not suppressed at all by the setup described so far.
Thanks to the high energy of the ions, these can be separated by methods borrowed from nuclear physics, like degrader foils and gas-filled magnets. Individual ions are detected by single-ion counting. Thanks to the high energy of the ions, these detectors can provide additional identification of background isobars by nuclear-charge determination; the above is just one example. There are other ways. L. W. Alvarez and Robert Cornog of the United States first used an accelerator as a mass spectrometer in 1939 when they employed a cyclotron to demonstrate that 3He was stable. In 1977, inspired by this early work, Richard A. Muller at the Lawrence Berkeley Laboratory recognised that modern accelerators could accelerate radioactive particles to an energy where the background interferences could be separated using particle identification techniques, he published the seminal paper in Science showing how accelerators could be used for detection of tritium and several other isotopes of scientific interest including 10Be.
His paper was the direct inspiration for other groups using cyclotrons and tandem linear accelerators. K. Purser and colleagues published the successful detection of radiocarbon using their tandem at Rochester. Soon afterwards the Berkeley and French teams reported the successful detection of 10Be, an isotope used in geology. Soon the accelerator technique, since it was more sensitive by a factor of about 1,000 supplanted the older “decay counting” methods for these and other radioisotopes; the applications are many. AMS is most employed to determine the concentration of 14C, e.g. by archaeologists for radiocarbon dating. An accelerator mass spectrometer is required over other forms of mass spectrometry due to their insufficient suppression of molecular isobars to resolve 13CH and 12CH2 from radiocarbon; because of the long half-life of 14C decay counting requires larger samples. 10Be, 26Al, 36Cl are used for surface exposure dating in geology. 3H, 14C, 36Cl, 129I are used as hydrological tracer.
Accelerator mass spectrometry is used in biomedical research. In particular 41Ca has been used to measure bone resorption in postmenopausal women. List of accelerator mass spectrometry facilities Arizona Accelerator Mass Spectrometry Laboratory
The Euphrates is the longest and one of the most important rivers of Western Asia. Together with the Tigris, it is one of the two defining rivers of Mesopotamia. Originating in eastern Turkey, the Euphrates flows through Syria and Iraq to join the Tigris in the Shatt al-Arab, which empties into the Persian Gulf; the Ancient Greek form Euphrátēs was adapted from Old Persian Ufrātu, itself from Elamite ú-ip-ra-tu-iš. The Elamite name is derived from a name spelt in cuneiform as, which read as Sumerian language is "Buranuna" and read as Akkadian language is "Purattu". In Akkadian the river was called Purattu, perpetuated in Semitic languages and in other nearby languages of the time; the Elamite and Sumerian forms are suggested to be from an unrecorded substrate language. Tamaz V. Gamkrelidze and Vyacheslav Ivanov suggest the Proto-Sumerian *burudu "copper" as an origin, with an explanation that Euphrates was the river by which the copper ore was transported in rafts, since Mesopotamia was the center of copper metallurgy during the period.
The earliest references to the Euphrates come from cuneiform texts found in Shuruppak and pre-Sargonic Nippur in southern Iraq and date to the mid-3rd millennium BCE. In these texts, written in Sumerian, the Euphrates is called Buranuna; the name could be written KIB. NUN. or dKIB. NUN, with the prefix "d" indicating that the river was a divinity. In Sumerian, the name of the city of Sippar in modern-day Iraq was written UD. KIB. NUN, indicating a strong relationship between the city and the river; the Euphrates is the longest river of Western Asia. It emerges from the confluence of the Kara Su or Western Euphrates and the Murat Su or Eastern Euphrates 10 kilometres upstream from the town of Keban in southeastern Turkey. Daoudy and Frenken put the length of the Euphrates from the source of the Murat River to the confluence with the Tigris at 3,000 kilometres, of which 1,230 kilometres is in Turkey, 710 kilometres in Syria and 1,060 kilometres in Iraq; the same figures are given by Mikhailova. The length of the Shatt al-Arab, which connects the Euphrates and the Tigris with the Persian Gulf, is given by various sources as 145–195 kilometres.
Both the Kara Su and the Murat Su rise northwest from Lake Van at elevations of 3,290 metres and 3,520 metres amsl, respectively. At the location of the Keban Dam, the two rivers, now combined into the Euphrates, have dropped to an elevation of 693 metres amsl. From Keban to the Syrian–Turkish border, the river drops another 368 metres over a distance of less than 600 kilometres. Once the Euphrates enters the Upper Mesopotamian plains, its grade drops significantly; the Euphrates receives most of its water in the form of rainfall and melting snow, resulting in peak volumes during the months April through May. Discharge in these two months accounts for 36 percent of the total annual discharge of the Euphrates, or 60–70 percent according to one source, while low runoff occurs in summer and autumn; the average natural annual flow of the Euphrates has been determined from early- and mid-twentieth century records as 20.9 cubic kilometres at Keban, 36.6 cubic kilometres at Hīt and 21.5 cubic kilometres at Hindiya.
However, these averages mask the high inter-annual variability in discharge. The discharge regime of the Euphrates has changed since the construction of the first dams in the 1970s. Data on Euphrates discharge collected after 1990 show the impact of the construction of the numerous dams in the Euphrates and of the increased withdrawal of water for irrigation. Average discharge at Hīt after 1990 has dropped to 356 cubic metres per second; the seasonal variability has changed. The pre-1990 peak volume recorded at Hīt was 7,510 cubic metres per second, while after 1990 it is only 2,514 cubic metres per second; the minimum volume at Hīt remained unchanged, rising from 55 cubic metres per second before 1990 to 58 cubic metres per second afterward. In Syria, three rivers add their water to the Euphrates; these rivers rise in the foothills of the Taurus Mountains along the Syro–Turkish border and add comparatively little water to the Euphrates. The Sajur is the smallest of these tributaries; the Balikh receives most of its water from a karstic spring near'Ayn al-'Arus and flows due south until it reaches the Euphrates at the city of Raqqa.
In terms of length