Karun in the context of "Khuzestan Province"

The Shatt al-Arab (Arabic: شط العرب, lit. 'River of the Arabs') is a river about 200 kilometres (120 mi) in length that is formed at the confluence of the Euphrates and Tigris rivers in the town of al-Qurnah in the Basra Governorate of southern Iraq. The southern end of the river constitutes the Iran–Iraq border down to its mouth, where it discharges into the Persian Gulf. The Shatt al-Arab varies in width from about 232 metres (761 ft) at Basra to 800 metres (2,600 ft) at its mouth. It is thought that the waterway formed relatively recently in geological time, with the Tigris and Euphrates originally emptying into the Persian Gulf via a channel further to the west. Kuwait's Bubiyan Island is part of the Shatt al-Arab delta.

The Karun, a tributary which joins the waterway from the Iranian side, deposits large amounts of silt into the river; this necessitates continuous dredging to keep it navigable.

Zard-Kuh (meaning "Yellow Mountain", also spelled Zardkuh, Zarduh Kuh or Zard Kuh-e Bakhtiari; Persian: زردکوه بختیاری) is a sub-range in the central Zagros Mountains, Iran.

With an elevation of 4,221 metres (13,848 ft), its highest peak "Kolonchin" is located in the Kuhrang County, in the Chaharmahal and Bakhtiari province of Iran. The Karun and also Zayanderud rivers originate in the Zagros Mountains near the Zard-Kuh. There are small glaciers on the mountain owing to the relatively high precipitation, which are the only glaciers in the subtropics outside the Himalayas, Andes and Trans-Mexican Volcanic Belt.

Characene (Ancient Greek: Χαρακηνή), also known as Mesene (Μεσσήνη) or Meshan, was a kingdom founded by the Iranian Hyspaosines located at the head of the Persian Gulf mostly within modern day Iraq. Its capital, Charax Spasinou (Χάραξ Σπασινού), was an important port for trade between Mesopotamia and India, and also provided port facilities for the city of Susa further up the Karun River. The kingdom was frequently a vassal of the Parthian Empire. Characene was mainly populated by Arabs, who spoke Aramaic as their cultural language. All rulers of the principality had Iranian names. Members of the Arsacid dynasty also ruled the state.

The Koohrang (also known as Kouhrang and Kurang) is a river originating in the Zagros mountains of western Iran, which joins the Beheštābād river (32°00′44″N 50°36′37″E / 32.01222°N 50.61028°E / 32.01222; 50.61028) to form the Karun, Iran's largest (by volume) river. A series of tunnels (Kuhrang Tunnels) have been built since the 1950s to redirect some of the Kuhrang's water toward the Zayandeh River to meet the demands of increased population in Esfahan and Yazd provinces.

The Zayandeh River basin encompasses about 41,500 square kilometres (16,000 sq mi) and is connected to the upper Karun River basin (which drains to the Persian Gulf) by the Kuhrang Dam and Tunnel 1 (32°26′10.94″N 50°06′04.50″E / 32.4363722°N 50.1012500°E / 32.4363722; 50.1012500 (Koorang Dam and Tunnel 1)) constructed in 1953 although first proposed in the early sixteenth century. Two additional tunnels (Kurang 2 and Kurang 3) were constructed in late 1990s and early 2000s. A hydroelectric dam at Godar-e Langar (also known as Karun-4) would also supply piped water to Esfahan 300 kilometres (190 mi) away if it is completed (Whitley and Gallagher, 1995). Dams have deleterious effects on a riverine fish and other fauna and are often stocked with exotic species. The upper Karun has not been well explored for endemic taxa. Mean annual flow of the Zayandeh River is estimated at 1.2 to 1.45 cubic kilometres (970,000 to 1,180,000 acre⋅ft) and is used mostly for agriculture, but an increase in population and industry has necessitated dam construction (Chadegan Reservoir, capacity 1.45 cubic kilometres (0.35 cu mi)) and diversion schemes. There is also the Hana Dam on the Hana River at Semirom with a height of 35 metres (115 ft) and a capacity of 45 million cubic metres (1.6×10 cu ft).

The Bahmanshir channel (Persian: بهمن‌شیر, IPA: [bæhmænˈʃiːɾ]) is a secondary estuary of the Karun River that parallels the Shatt al-Arab/Arvand Rud waterway on the far side of the Abadan Island, Iran, for 70 miles before emptying into the Persian Gulf.

The Bahamanshir served as the main estuary of the Karun River before the digging of the Haffar canal, by the Daylamite Buwayhid king Panah Khusraw Adud ad-Dawlah, that joined the Karun to the Arvand Rud / Shatt al-Arab waterway at the site of the present-day Khorramshahr. The Haffar in time became the main estuary of the Karun, relegating the Bahmanshir to a secondary estuary status.

Haffar is a canal in Iran.

During the early Islamic centuries, the Daylamite Buwayhid king, Panah Khusraw Adud ad-Dawlah, ordered the digging of a canal to join the Karun River, which at the time emptied independently into the Persian Gulf through the Bahmanshir channel, to the Shatt al-Arab waterway (known as Arvand Rud in Iran), the joint estuary of the Tigris and Euphrates rivers. The extra water from the Karun, which, at times during the spring melt, discharged over 27 times the volume of the Tigris-Euphrates water that reaches the Shatt al-Arab) makes the joint estuary more reliably navigable.

Khorramshahr (Persian: خرمشهر; [xoræmˈʃæhɾ]) is a city in the Central District of Khorramshahr County, Khuzestan province, Iran, serving as capital of both the county and the district. It is also known in Arabic by the local ethnically Arab population as Al-Muhammarah (Arabic: المحمرة).

Khorramshahr is an inland port city located approximately 10 kilometres (6.2 mi) north of Abadan. The city extends to the right bank of the Shatt Al Arab waterway near its confluence with the Haffar arm of the Karun river. The city was destroyed in the Iran–Iraq War, with the 1986 census recording a population of zero. Khorramshahr was rebuilt after the war, and more recent censuses show that the population has returned to the pre-war level.