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42-794: The first irrigation works along the Diyala River were undertaken in Parthian times. Indeed, it may be that the lower part of the Nahrawan Canal was originally the lower course of the Diyala. The large-scale canal system of early medieval times however was created in the reign of the Sassanid ruler Khosrow I ( r.  531–579 ), who also established it as a separate administrative district ( Bazidjan Khusraw ). A treasury and mint were possibly established there. In early Islamic times,

84-750: A river and tributary of the Tigris . It is formed by the confluence of the Sirwan and Tanjaro rivers in Darbandikhan Dam in the Sulaymaniyah Governorate of Northern Iraq. It covers a total distance of 445 km (277 mi). It rises near Hamadan , in the Zagros Mountains of Iran. It then descends through the mountains, where for some 32 km it forms the border between the two countries. It finally flows into

126-571: A brightly coloured pottery with pictorial representations, was typical of sites along the Diyala River. It developed around 2800 BC, and is related to the Jemdet Nasr ware in central Mesopotamia of the same period. The red colour was achieved predominantly by using haematite paint. Scarlet Ware is typical of Early Dynastic I and II periods. Along the Diyala is located one of the most important trade routes linking south Mesopotamia with

168-488: A negative effect on fish species that migrate as part of their breeding cycle (e.g., salmonids ), but it also can be useful as a method of preventing invasive species moving upstream. For example, weirs in the Great Lakes region have helped to prevent invasive sea lamprey from colonising farther upstream. Mill ponds are created by a weir that impounds water that then flows over the structure. The energy created by

210-415: A range of biota , including poor swimmers. Even though the water around weirs can often appear relatively calm, they can be extremely dangerous places to boat, swim, or wade, as the circulation patterns on the downstream side—typically called a hydraulic jump —can submerge a person indefinitely. This phenomenon is so well known to canoeists, kayakers, and others who spend time on rivers that they even have

252-416: A rueful name for weirs: "drowning machines". The Ohio DNR recommends that a victim should "tuck the chin down, draw the knees up to the chest with arms wrapped around them. Hopefully, conditions will be such that the current will push the victim along the bed of the river until swept beyond the boil line and released by the hydraulic." The Pennsylvania State Police also recommends to victims, "curl up, dive to

294-449: A weir is broad-crested for much of its length, but has a section where the weir stops or is 'open' so that small boats and fish can traverse the structure. A notch weir is any weir where the physical barrier is significantly higher than the water level except for a specific notch (often V-shaped) cut into the panel. At times of normal flow all the water must pass through the notch, simplifying flow volume calculations, and at times of flood

336-410: Is Wehr , which means the same as English weir. Commonly, weirs are used to prevent flooding , measure water discharge, and help render rivers more navigable by boat. In some locations, the terms dam and weir are synonymous, but normally there is a clear distinction made between the structures. Usually, a dam is designed specifically to impound water behind a wall, whilst a weir is designed to alter

378-405: Is a flat-crested structure, where the water passes over a crest that covers much or all of the channel width. This is one of the most common types of weir found worldwide. A compound weir is any weir that comprises several different designs into one structure. They are commonly seen in locations where a river has multiple users who may need to bypass the structure. A common design would be one where

420-473: Is a generic relationship and specific calculations are available for the many different types of weir. Flow measurement weirs must be well maintained if they are to remain accurate. The flow over a V-notch weir (in ft /s) is given by the Kindsvater–Shen equation: where As weirs are a physical barrier, they can impede the longitudinal movement of fish and other animals up and down a river. This can have

462-702: Is mentioned in Herodotus ' Histories under the name Gyndes, where it is stated that the king Cyrus the Great dispersed it by digging 360 channels as punishment after a sacred white horse perished there. The river returned to its former proportions after the channels disappeared under the sand. In March 1917 the British Empire defeated the Ottoman Empire at the confluence with the Tigris, leading to

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504-622: The Fall of Baghdad , part of the Mesopotamian Campaign of World War I. Major excavations were done in the lower Diyala river basin in the 1930s. They were conducted by the University of Chicago Oriental Institute (1930–1937) and by the University of Pennsylvania (1938–1939). The sites such as Tell Agrab , Tell Asmar (ancient Eshnunna ), Ishchali (ancient Neribtum), and Khafaje (ancient Tutub ) were excavated. At that time,

546-528: The 48 km (30 mi) long Nosoud Water Conveyance Tunnel and to produce hydroelectric power. In Iraq, the river first reaches the Darbandikhan Dam which generates hydroelectric power and stores water for irrigation. It then flows down to the Hemrin Dam for similar purposes. In the lower Diyala Valley near Baghdad the river is controlled by the Diyala Weir which controls floods and irrigates

588-424: The Diyala was relatively unexplored compared to southern and northern Mesopotamia. But looting of sites was already underway. As the result, the professional excavations were launched. Archaeologists James Breasted and Henri Frankfort were leading these projects. These excavations provided very comprehensive data on Mesopotamian archaeology and chronology. They covered the time between the late Uruk period and

630-735: The Iranian plateau. Thus, Scarlet ware was also popular in Pusht-i Kuh, Luristan , and it was traded to Susa during Susa II period. During the Larsa period, Eshnunna especially became prominent. The Diyala river also bore the name "Shu-durul" at the time. In 693 BC, the Battle of Diyala River took place between the forces of the Assyrians and the Elamites of southern Iran. The river

672-531: The Nahr Bin, connected Jisr al-Nahrawan with Kalwadha south of Baghdad. Just south of Jisr al-Nahrawan there was another canal, the Diyala canal—the present course of the namesake river—which joined the Tigris some 5 km south of Baghdad. Jisr al-Nahrawan itself was a wealthy place, as there the Khurasan Road connecting Baghdad with Central Asia crossed the canal. Surviving descriptions record that it

714-563: The Nahrawan canal was simply the most dramatic example of a widespread phenomenon of the time; and it was symbolic of the end of ‘Abbasid power just as the breach of the Marib Dam was of the end of the prosperity of pre-Islamic south Arabia ". The lower and middle Nahrawan were entirely abandoned for almost 14 years, until the Buyids under Mu'izz al-Dawla restored the canal. Nevertheless,

756-538: The Tigris below Baghdad . Navigation of the upper reaches of the Diyala is not possible because of its narrow defiles , but the river's valley provides an important trade route between Iran and Iraq. The river flows southwest of the Hamrin Mountains . Its Aramaic origin is "Diyalas" and in Kurdish it is called "Sirwan", meaning 'roaring sea' or 'shouting river'. In early Islamic period, the lower course of

798-556: The Tigris, the Yahudi ('of the Jews'), the al-Ma'muni, named after Caliph al-Ma'mun ( r.  813–833 ), and the largest of the three, the Abu al-Jund ('father of the army'), built under Harun al-Rashid ( r.  786–809 ). Some 20 km south of the inflow of the Abu al-Jund stood the town of Salwa or Bab Salwa (Basalwa), and a little further on the town of Ba'quba , the capital of

840-625: The Upper Nahrawan district, some 50 km north-northeast of Baghdad. From there, the main canal, now known as the Tamarra, turned south to the towns of Bajisra (originally Bayt al-Jisr , 'bridge-house') and finally Jisr al-Nahrawan, from where it was known as the Nahrawan proper. From Bajisra a canal, the Nahr al-Khalis, connected the main canal with the Tigris at Baradan and supplied the eastern suburbs of Baghdad with water, while another,

882-512: The area northeast of Baghdad. 33°13′15″N 44°30′23″E  /  33.2208°N 44.5064°E  / 33.2208; 44.5064 Weir A weir / w ɪər / or low-head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the river level. Weirs are also used to control the flow of water for outlets of lakes, ponds, and reservoirs. There are many weir designs, but commonly water flows freely over

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924-502: The bottom, and swim or crawl downstream". As the hydraulic jump entrains air, the buoyancy of the water between the dam and boil line will be reduced by upward of 30%, and if a victim is unable to float, escape at the base of the dam may be the only option for survival. There are many different types of weirs and they can vary from a simple stone structure that is barely noticeable, to elaborate and very large structures that require extensive management and maintenance. A broad-crested weir

966-528: The canal network continued to decline thereafter. As late as 1140, the Seljuk governor Bihruz tried to restore it, but according to the 13th-century scholar Yaqut al-Hamawi , infighting among the Seljuks once again meant the neglect of the canal, and its use as a road by their troops compounded the destruction of the network. By Yaqut's time, the canal network had largely silted up and the countryside along them

1008-501: The change in height of the water can then be used to power waterwheels and power sawmills, grinding wheels, and other equipment. Weirs are commonly used to control the flow rates of rivers during periods of high discharge. Sluice gates (or in some cases the height of the weir crest) can be altered to increase or decrease the volume of water flowing downstream. Weirs for this purpose are commonly found upstream of towns and villages and can either be automated or manually operated. By slowing

1050-399: The city of Iskaf Bani Junayd , divided by the canal in upper and lower towns. From Iskaf, the canal went on for another 100 km amidst a heavily cultivated landscape to rejoin the Tigris at Madharaya, near modern Kut . Diyala River The Diyala ( Arabic : نهر ديالى ‎ Nahr Diyālā ; Kurdish : Sîrwan ; Farsi : دیاله Diyâlah , سيروان Sīrvān ) is

1092-414: The design of a weir that ensure that fish can bypass the barriers and access upstream habitats. Unlike dams, weirs do not usually prevent downstream fish migration (as water flows over the top and allows fish to bypass the structure in that water), although they can create flow conditions that injure juvenile fish. Recent studies suggest that navigation locks have also potential to provide increased access for

1134-552: The end of the Old Babylonian period (3000–1700 BC). Subsequently, nine detailed monographs were published, but most of the objects, numbering 12,000, remained unpublished. Launched in 1992, the Diyala Database Project has been publishing a lot of this material. Other scholars who worked there were Thorkild Jacobsen as epigrapher, Seton Lloyd , and Pinhas Delougaz . Around 1980, the Diyala region

1176-399: The largest may be many metres tall and hundreds of metres long. Some common weir purposes are outlined below. Weirs allow hydrologists and engineers a simple method of measuring the volumetric flow rate in small to medium-sized streams/rivers or in industrial discharge locations. Since the geometry of the top of the weir is known and all water flows over the weir, the depth of water behind

1218-423: The maximum height a species can jump or creates flow conditions that cannot be bypassed (e.g., due to excessive water velocity) effectively limits the maximum point upstream that fish can migrate. In some cases this can mean that huge lengths of breeding habitat are lost, and over time this can have a significant impact on fish populations. In many countries, it is now a legal requirement to build fish ladders into

1260-413: The rate at which water moves downstream even slightly, a disproportionate effect can be had on the likelihood of flooding. On larger rivers, a weir can also alter the flow characteristics of the waterway to the point that vessels are able to navigate areas previously inaccessible due to extreme currents or eddies . Many larger weirs will have construction features that allow boats and river users to "shoot

1302-513: The region was divided into three tax districts, Upper, Middle and Lower Nahrawan. The canal was breached in 937/8, during the revolt of Bajkam against Ibn Ra'iq ; the latter tried to impede Bajkam's advance from Wasit to Baghdad by flooding the region in between. The move barely obstructed Bajkam, but succeeded in destroying the agriculture of the region, hitherto the breadbasket of the Abbasid capital. As Hugh N. Kennedy writes, "the breach of

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1344-427: The river bottom) that reduces the water oxygen content and smothers invertebrate habitat and fish spawning sites. The oxygen content typically returns to normal once water has passed over the weir crest (although it can be hyper-oxygenated), although increased river velocity can scour the river bed causing erosion and habitat loss. Weirs can have a significant effect on fish migration . Any weir that exceeds either

1386-403: The river flow characteristics. A common distinction between dams and weirs is that water flows over the top (crest) of a weir or underneath it for at least some of its length. Accordingly, the crest of an overflow spillway on a large dam may therefore be referred to as a weir. Weirs can vary in size both horizontally and vertically, with the smallest being only a few centimetres in height whilst

1428-778: The river formed part of the Nahrawan Canal . The Diyala Governorate in Iraq is named after the river. It may be the ancient Tornas river. This area flourished already during the Jemdet Nasr and Early Dynastic periods , through to the Akkadian period . In Eshnunna (Tell Asmar) , the Tell Asmar Hoard is particularly notable. Twelve remarkable statues were found belonging to the Early Dynastic period (2900–2350 BC). A type of pottery known as 'Scarlet Ware',

1470-443: The top of the weir crest before cascading down to a lower level. There is no single definition as to what constitutes a weir. Weir can also refer to the skimmer found in most in-ground swimming pools, which controls the flow of water pulled into the filtering system. The word likely originated from Middle English were , Old English wer , a derivative of the root of the verb werian, meaning "to defend, dam". The German cognate

1512-579: The town of Jisr al-Nahrawan in the middle of the canal was the site of the Battle of Nahrawan on 17 July 658 between Rashidun caliph Ali and the Kharijites under Abd Allah ibn Wahb. Under the early Caliphates , and especially under the Abbasids who made nearby Baghdad their capital, the canal network was repaired and expanded, reaching its peak in the 9th and early 10th centuries. In Abbasid times,

1554-515: The water level can rise and submerge the weir without any alterations made to the structure. A polynomial weir is a weir that has a geometry defined by a polynomial equation of any order n . In practice, most weirs are low-order polynomial weirs. The standard rectangular weir is, for example, a polynomial weir of order zero. The triangular (V-notch) and trapezoidal weirs are of order one. High-order polynomial weirs are providing wider range of Head-Discharge relationships, and hence better control of

1596-496: The weir can be converted to a rate of flow. However, this can only be achieved in locations where all water flows over the top of the weir crest (as opposed to around the sides or through conduits or sluices) and at locations where the water that flows over the crest is carried away from the structure. If these conditions are not met, it can make flow measurement complicated, inaccurate, or even impossible. The discharge calculation can be summarised as where However, this calculation

1638-546: The weir" and navigate by passing up or down stream without having to exit the river. Weirs constructed for this purpose are especially common on the River Thames , and most are situated near each of the river's 45 locks . Because a weir impounds water behind it and alters the flow regime of the river, it can have an effect on the local ecology . Typically, the reduced river velocity upstream can lead to increased siltation (deposition of fine particles of silt and clay on

1680-457: Was abandoned. In medieval times, the main canal was divided into three sections, described in detail by al-Hamawi, in his Mu'jam al-Buldan . The initial feeder canal drawing water from the Tigris at Dur al-Arabaya near Samarra and carrying it to the Diyala at Ba'quba was called al-katul al-kisrawi ('the Cut of Khosrau'). During its course, it was joined by three smaller canals taken from

1722-632: Was also explored intensively as part of the Hamrin Dam Salvage Project. The following sites were excavated from 1977 to 1981: Tell Yelkhi , Tell Hassan, Tell Abu Husaini, Tell Kesaran, Tell Harbud, Tell al-Sarah, and Tell Mahmud. In Iran the Daryan Dam is constructed near Daryan in Kermanshah Province . One of the goals of the dam is to divert a portion of the water to Southwestern Iran for irrigation through

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1764-404: Was extended on both sides of the canal, each with its own mosques, markets and hostels for travellers and pilgrims. It was abandoned by the 14th century, as the road to Khurasan was diverted north, through Ba'quba. Below Jisr al-Nahrawan came a large Sasanian-era weir ( Shadhurwan ), followed by the towns of Jisr Buran/Puran (named after al-Ma'mun's wife), Yarzatiya, 'Abarta, another weir, and

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