| Little Zab | |
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| Location | |
| Country | Iran,Iraq |
| Region | Iraqi Kurdistan |
| District | Erbil Governorate |
| Municipality | Erbil |
| Physical characteristics | |
| Source | |
| • location | Zagros Mountains,Iran |
| • elevation | 3,000 m (9,800 ft)approx. |
| Mouth | |
• location | Tigris,Kirkuk Governorate,Iraq |
• coordinates | 35°14′17″N43°26′11″E / 35.23806°N 43.43639°E /35.23806; 43.43639 |
| Length | 400 km (250 mi)approx. |
| Basin size | 22,000 km2 (8,500 sq mi)approx. |
| Discharge | |
| • average | 197.8 m3/s (6,990 cu ft/s) |
| • maximum | 3,420 m3/s (121,000 cu ft/s) |
| Basin features | |
| Tributaries | |
| • left | Baneh, Qala Chulan, Rubar-i-Basalam |
TheLittle Zab orLower Zab (Arabic:الزاب الاسفل,al-Zāb al-Asfal;Kurdish:Zêy Koya orZêyê Biçûk;Persian:زاب کوچک,Zâb-e Kuchak;Syriac:ܙܒܐ ܬܚܬܝܐ,Zāba Taḥtāya) is a river that originates inIran and joins theTigris just south ofAl Zab in theKurdistan region ofIraq. The Little Zab is approximately 400 kilometres (250 mi) long and drains an area of about 22,000 square kilometres (8,500 sq mi). The river is fed by rainfall and snowmelt, resulting in a peakdischarge in the spring and low water in the summer and early fall. Two dams built on the Little Zab regulate the river flow, providing water forirrigation and generatinghydroelectricity. TheZagros Mountains have been populated since at least theLower Palaeolithic, but the earliest archaeological site in the Little Zab basin, Barda Balka, dates to theMiddle Palaeolithic. Human occupation of the Little Zab basin has been attested for every period since then.
The Little Zab rises in the Mountains in Iraq at an elevation of circa 3,000 metres (9,800 ft)amsl.[2] In its upper reaches, the course of the Little Zab is determined by the alignment of the major mountain chains that make up the Zagros. Thus, the river flows through valleys that are predominantly aligned along a northwest–southeast axis, parallel to the major mountain chains of the Zagros, only to change its direction abruptly where it cuts through these chains in narrow gorges.[3] Along the way, it collects the waters coming down from the eastern face of theQandil Mountains, which now form the border between Iran and Iraq.[4]: 62 The Little Zab enters the Mesopotamian plain south of Dukan, where it first assumes a roughly westward course before turning to the southwest upstream from the town of Altun Kopru and uniting with the Tigris near the town ofAl Zab.[5] Most tributaries join the Little Zab upstream from Dukan, with the largest being the Baneh River and the Qala Chulan.[3] A number of smaller streams joined the Little Zab in theRanya Plain, which is now partly inundated byLake Dukan.[6]
Different estimates have been given for the length of the Little Zab: 380 kilometres (240 mi),[7] 400 kilometres (250 mi)[8] and 456 kilometres (283 mi).[2][9] For a short distance, the Little Zab forms the border between Iran and Iraq, and along its lower course it also constitutes the border betweenErbil Governorate andSulaymaniyah Governorate, and Erbil andKirkuk Governorates. The river is fed by snowmelt and rainfall, resulting in a peak discharge in the period February–May. Low water levels are recorded for the period July–October. The average discharge of the Little Zab is 197.8 cubic metres (6,990 cu ft) per second, whereas the maximum recorded discharge is 3,420 cubic metres (121,000 cu ft) per second. Average annual discharge is 7.2 cubic kilometres (1.7 cu mi).[8][10][11] Because of its torrential nature, Medieval Arab geographers have described the Little Zab, and theGreat Zab as well, as "demoniacally possessed".[1]
Thedrainage basin of the Little Zab covers 21,475–22,250 square kilometres (8,292–8,591 sq mi);[2][12] from the location where theDukan Dam has been constructed, it measures 11,700 square kilometres (4,500 sq mi).[10] The larger part of the basin (74%) is located within Iraqi borders; the remainder is in Iran.[12] On the north, it is bordered by the Great Zab basin while on the south it is adjoined by the basins of theAdhaim andDiyala rivers. The parallel mountain ranges of the Zagros consist oflimestonefolds rising to elevations over 3,000 metres (9,800 ft).Water erosion has filled the Little Zab valley and thefoothill zone south-west of the Zagros with layers ofgravel,conglomerate, andsandstone. The Ranya Plain is the largest valley in the Little Zab drainage basin, and the second-largest in the Iraqi Zagros behind theShahrazor.[13][14]
The Little Zab crosses very diverse climatic and ecological zones. Annual precipitation along the course of the river diminishes from over 1,000 millimetres (39 in) in the Iranian Zagros to less than 200 millimetres (7.9 in) at the confluence with the Tigris nearAl Zab.[15] Average temperatures follow a similar gradient, with the mountain valleys generally experiencing colder winters than the foothill zone, while summers in the latter are hotter.[16] In the high Zagros, three differentbiomes can be distinguished. Thetree line is at approximately 1,800 metres (5,900 ft); above which herbs and shrubs predominate. The dominant vegetation between 1,800 and 610 metres (5,910 and 2,000 ft) was an open oak forest (Quercus aegilops), but not much of this original vegetation remains. The river valleys are characterized by water-loving plants, and marshy areas were in the past – in the absence of drainage – prone tomalaria.[17][18][19] Although the foothill zone, especially the plain of Erbil, is heavily cultivated, patches of natural vegetation remain, with herbs in the genusPhlomis being very common.[20]
Two dams have been constructed on the Little Zab in Iraq while Iran is currently constructing one with two others planned. The two in Iraq are the Dukan Dam and theDibis Dam. The Dukan Dam was constructed between 1957 and 1961 as a multi-purposearch dam upstream from the town of Dukan. The dam's crest is 116 metres (381 ft) above the riverbed (516 metres (1,693 ft) amsl) and 360 metres (1,180 ft) long. Its functions are to regulate the flow of the Little Zab, to store water for irrigation in itsreservoir (Lake Dukan) and to provide hydroelectric power. The maximum storage capacity of the dam's reservoir is 6.97 cubic kilometres (1.67 cu mi).[10][21] Because the flooding of Lake Dukan would lead to the submersion of numerous archaeological sites, anarchaeological survey andrescue excavations were carried out in the endangered region – notably at the sites ofTell Shemshara andTell Bazmusian.[22][23] TheDibis Dam is located approximately 130 kilometres (81 mi) upstream from the confluence with the Tigris and was constructed between 1960 and 1965. Theembankment dam is 376 metres (1,234 ft) long and 23.75 metres (77.9 ft) wide and provides water for theKirkuk Irrigation Project.[24] Currently under construction in Iran is theSardasht Dam. Construction began in 2011 and when complete, the 116 m (381 ft) tallembankment dam will support a 120 MW power station. Above the Sardasht Dam, Iran is planning to construct the Shivahan and Garjhal Dams with the primary purpose of power generation.[25][26][27][28][29]
Iran has diverted as much as 600,000,000 cubic metres (2.1×1010 cu ft) of its water in efforts to restoreLake Urmia. This competes with need for the water inKurdistan Region in Iraq.[30]
AlthoughIraqi Kurdistan is not well known from an archaeological point of view, the available evidence nevertheless shows that the relatively favourable ecological conditions of the Iraqi part of the Zagros attracted human groups from early prehistory onwards.[31] Lower Palaeolithic archaeological sites have to date not been found in the Iraqi part of the Zagros Mountains, but they are known from the Iranian side where numerous cave sites have been found during archaeological surveys.[32] Information on the early prehistory of the wider Little Zab region itself comes from theexcavations carried out by theOriental Institute at archaeological sites east ofKirkuk and south of the Little Zab. The earliest evidence for human occupation in this region comes from the Middle Palaeolithic site ofBarda Balka, where LateAcheulean stone tools have been found.[33] Archaeological research elsewhere in the Zagros confirms the importance of this area to early humanhunter-gatherers – including groups ofNeanderthals as evidenced by the finds inShanidar Cave in the Great Zab basin.[34][35]Mousterian stone tools that were used by either Neanderthals oranatomically modern humans have recently been excavated inErbil, between the Little Zab and the Great Zab.[36] Both open-air and cave sites are attested for theZarzian culture, which straddles theUpper andEpipalaeolithic periods. After the Zarzian, the focus of human occupation shifted from cave-sites, which continue to be used as secondary or seasonal occupation sites up to today, to open-air sites and it was in this period that the trend towarddomestication of plants and animals set in.[37] Domestication of the goat probably occurred first in this area of the Zagros.[38]Jarmo, atell east of Kirkuk, was aNeolithic village community that practiced agriculture and animal husbandry.[39] Pottery occurs from the early occupation levels onward; in its later phases it resembles pottery fromHassuna. The early occupation of Tell Shemshara, in the Ranya Plain, can also be dated to this period.[40][41] The archaeological fieldwork in the Ranya Plain showed that this area was occupied during theUbaid,Uruk and Ninevite V periods – roughly from the middle 6th to the mid-3rd millennium BCE.[42] Evidence for these periods comes from theCitadel of Erbil as well.[43]
The region enters history at the end of the 3rd millennium BCE, when Erbil is mentioned as Urbilum by kingShulgi of theUr III dynasty.[44] From that time onward, the Little Zab basin became increasingly entangled in the affairs of the successive Mesopotamian empires that sought control over the Zagros Mountains. In the early second millennium BCE, kingShamshi-Adad of Upper Mesopotamia waged war to the land ofQabra, which was probably located along the lower course of the Little Zab, and installed garrisons in the conquered towns. The archive ofclay tablets found at Tell Shemshara (ancient Shusharra) shows that the local governor switched allegiance and became a vassal of Shamshi-Adad.[45] During the 14th century BCE, the region was part of theMitannian kingdom, with sites likeNuzi andTell al-Fakhar, south of the Little Zab, yieldingclay tablet archives for this period.[46] During the late second–early first millennia BCE, the lower Little Zab basin belonged to the heartland of theMiddle Assyrian andNeo-Assyrian empires. After the fall of the Neo-Assyrian Empire, control of the Zagros shifted first to theMedes and in 550 BCE to theAchaemenid Empire.[47] The last Achaemenid rulerDarius III was defeated byAlexander the Great at theBattle of Gaugamela in northern Iraq and after Alexander's death in 323, the area fell to hisSeleucid successors.[48]
On theOrteliusTheatrum Orbis Terrarum maps of Turkish Empire and Persian Kingdom it is listed asNoue aque fl.
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