Variants of name
- Eulaeus River (Greek)
- Eulaeus/Eulæus (Greek)
- Kara Su
- Gihon—one of the four rivers of Eden/Paradise to the Bible and as the Choaspes in ancient times;
It rises in the Zagros Mountains, and passes west of Shush (ancient Susa), eventually falling in ancient times into the Tigris just below its confluence with the Euphrates very near to the Iran-Iraq border. The river is currently the location of the Karkheh Dam and hydro-power plant in Iran.
In modern times, after approaching within 16 kilometres of the Dez River, it turns to the southwest and then, northwest of Ahvaz, turns northwest and is absorbed by the Hawizeh Marshes that straddle the Iran–Iraq border. Its peculiarly sweet water was sacred to the use of the Persian kings. Ancient names for the Karkheh should be treated as conjectural because the bed of the river has changed in historic times, and because a nearby watercourse between the Karkheh and the Dez River, the Shaur, confuses the identification.
The problem with the ancient names is that while the Karkheh flows a kilometre or two west of Susa, another major watercourse flows parallel to the Karkheh within a few kilometres east of Susa. When these rivers are in flood stage, the entire area south of Susa can be flooded, as the waters of the two watercourses mingle. The watercourse a kilometre or two east of Susa, now called the Shaur, flows east between the Haft Tepe and Shaur ridges into the Dez River, north of where the Dez and Karun rivers merge. At some previous time, the Karkheh may have joined the eastern end of the Shaur. The timing of these changes is not known with any certainty. The ancient name of the Shaur may have been the Choaspes.
Arrian writes....Alexander now ordered Hephaestion to lead the main body of the infantry as far as the Persian Sea, while he himself, his fleet having sailed up into the land of Susiana, embarked, with the shield-bearing guards and the body-guard of infantry; and having also put on board a few of the cavalry Companions, he sailed down the river Eulaeus to the sea. When he was near the place where the river discharges itself into the deep, he left there most of his ships, including those which were in need of repair, and with those especially adapted for fast sailing he coasted along out of the river Eulaeus through the sea to the mouth of the Tigres. The rest of the ships were conveyed down the Eulaeus as far as the canal which has been cut from the Tigres into the Eulaeus, and by this means they were brought into the Tigres. Of the rivers Euphrates and Tigres which enclose Syria between them, whence also its name is called by the natives Mesopotamia, the Tigres flows in a much lower channel than the Euphrates, from which it receives many canals; and after taking up many tributaries and its waters being swelled by them, it falls into the Persian Sea. It is a large river and can be crossed on foot nowhere as far as its mouth, inasmuch as none of its water is used up by irrigation of the country. For the land through which it flows is more elevated than its water, and it is not drawn off into canals or into another river, but rather receives them into itself. It is nowhere possible to irrigate the land from it. But the Euphrates flows in an elevated channel, and is everywhere on a level with the land through which it passes. Many canals have been made from it, some of which are always kept flowing, and from which the inhabitants on both banks supply themselves with water; others the people make only when requisite to irrigate the land, when they are in need of water from drought. For this country is usually free from rain. The consequence is, that the Euphrates at last has only a small volume of water, which disappears into a marsh. Alexander sailed over the sea round the shore of the Persian Gulf lying between the rivers Eulaeus and Tigres; and thence he sailed up the latter river as far as the camp where Hephaestion had settled with all his forces. Thence he sailed again to Opis, a city situated on that river. In his voyage up he destroyed the weirs which existed in the river, and thus made the stream quite level. These weira had been constructed by the Persians, to prevent any enemy having a superior naval force from sailing up from the sea into their country. The Persians had had recourse to these contrivances because they were not a nautical people; and thus by making an unbroken succession of weirs they had rendered the voyage up the Tigres a matter of impossibility. But Alexander said that such devices were unbecoming to men who are victorious in battle; and therefore he considered this means of safety unsuitable for him; and by easily demolishing the laborious work of the Persians, he proved in fact that what they thought a protection was unworthy of the name.
1. The Eulaeus is now called Kara Su. After joining the Ooprates it was called Pasitigris. It formerly discharged itself into the Persian Gulf, but now into the Shat-el-Arab, as the united stream of the Euphrates and Tigris is now called. In Dan. viii. 2, 16, it is called Ulai. Cf. Pliny, vi. 26, 31; xxxi. 21.
2. The Greeks and Romans sometimes speak of Mesopotamia as a part of Syria, and at other times they call it a part of Assyria. The Hebrew and native name of this country was Aram Naharaim, or "Syria of the two rivers."
4. Cf. Arrian, iii. 7, supra; Curtius, iv. 37.
5. Cf. Strabo, xvi. 1; Herodotus, i, 193; Ammianus, xxiv. 3, 14.
6. Probably this city stood at the junction of the Tigris with the Physcus, or Odoneh. See Xenophon (Anab. ii. 4, 26); Herodotus, i. 189; Strabo, (xvi. 1) says that Alexander made the Tigris navigable up to Opis.
- Bosworth, A. B. (1993). Conquest and Empire: The Reign of Alexander the Great. Cambridge University Press. p. 88. ISBN 0-521-40679-X.
- Potts, Daniel T. (1999). The Archaeology of Elam: Formation and Transformation of an Ancient Iranian State. Cambridge University Press. p. 236. ISBN 0-521-56496-4. "One refers to his camp while on campaign and to action near the Ulai, the modern Karkheh river, in Khuzistan"
- Hazlitt, William (1851). "page 108". The Classical Gazetteer. Archived from the original on 2007-03-03.
- John Hansman, "Charax and the Karkheh," Iranica Antiqua VII(1967), pp.21-58, and Michael J. Kirkby, "Land and Water Resources of the Deh Luran and Khuzistan Plains," Appendix I, in Studies in the Archaeological History of the Deh Luran Plain. The Excavation of Chagha Sefid, edited by Frank Hole, pp. 251-288. Memoirs, no. 9, Ann Arbor, Museum of Anthropology, University of Michigan
- The Anabasis of Alexander/7a, Ch.7