The Iranian rivers can be divided into the following groups:
Caspian Sea group
Most of the rivers in this zone originate from the northern slopes of Alborz Mountain Range. With the exception of rivers flowing to the sea from east or west because of closeness to the sea these rivers are short in length:
The length of Aras River is 1,072 kilometers. This river originates from Hezarberkeh Mountain Range in Turkey and forms the border line between Iran and Azerbaijan Republic in the Qaradooni region and pours into Caspian Sea. Maku, Khooni and Maraud rivers join Aras River before reaching the Caspian Sea.
The Ancient Greek name of this river was Amardos and it was called Nahre-ul-Beiz by Arabs. During the medieval ages the whole river was called Sefidrood but nowadays only that part of the river falling between Manjil and Caspian Sea (with a length of 765 km) is called Sefidrood. Sefldrood originates from Chehel Cheshmeh Mountain Range in Kurdestan Province.
The length of Chalus River is 72 km and it originates from Taleghan and Kandovan mountains.
With a length of 150 km Haraz River originates from Lar Valley north of Damavand. Its main tributary is Noor which joins Haraz at Kialooband. After passing Amol Haraz River pours into Caspian Sea at Babolsar.
The length of this river is approximately 101.5 km. It originates from Savadkuh Mountain at Alborz Mountain Range and pours into Caspian Sea at Babolsar.
The length of this river is 143 km. It originates from Savadkuh Mountain and pours into Caspian Sea after passing Ghaemshahr.
With a length of 140 km Tajan River begins in Rood bar near Hezarjerib and after passing Sari it pours into Caspian Sea near Farahabad.
This river is 176 km long. It originates from Shahkuh Mountain in Gorgan and pours into Gorgan Gulf.
With a length of 300 km Gorgan River springs from Aladagh Mountain Range and after passing Kukalan and Jorjan it divides into two branches and pours into Gorgan Gulf.
This river originates from Chehel Nabalghan Mountains in Nahavand. Mahidasht, Karand, Gharesoo and Dinor tributaries join Gamasab River in Kermanshah. After Sirvan the river changes its name to Simreh River. Its major tributary in Lorestan is Lashkanrud River. After reaching Pay-e Pol Simreh, River changes its name to Karkheh (ancient Xoaspes) River. Karkheh passes the moats in the Iranian border with Iraq and pours into Tigris River. Having a length of 875 km Karkheh River is one of the longest rivers in Iran.
With a length of 950 km Karun and its branches form the longest river in Iran. Being deep enough Karun is the only river in Iran which is suitable for navigation. Its originates from Zardkuh Mountain in Chaharmahal and Dez River which joins Karun River near Qir Port is its most important tributary. After passing Ahwaz, Karun divides into two branches: Bahmanshir River which pours into Persian Gulf and Karun River which joins Arvandrud River near Khorramshahr. (In ancient times Karun was known as Pasitigris River).
Jarahi River is formed of two tributaries i.e. Abzolal and Maroonrud. They originate from the eastern mountains of Khuzestan Province and after joining each other they form the Jarahi River. After passing Doorgh Moat the river divided into Shadgan and Jarahi branches. Shadgan joins Karun River and keeping is original name (Jarahi) the other branch pours into Khoor Musa Estuary in Persian Gulf. The length of that part of the river which is called Jarahi is 438 km.
Zohre or Hendijan River
With a length of 490 km, this river originates from Kohgilooye Mountain and pours into Persian Gulf.
Dalaki River originates from the mountains in Arzhan Plain. It is formed of two tributaries: Dalaki and Shapur. The two tributaries join each other at Kulal region, form the Dalaki River and pour into Persian Gulf. The total length of Dalaki River is 170 km.
With a length of 187 km Mand River originates from the mountains northwest of Shiraz. Then it divides into several branches and pours into Persian Gulf at Ziarat Village.
Naband originates from Larestan Mountains and pours into a small gulf known as Naband Estuary in Persian Gulf.
With a length of 66 km Mehran River originates from Lar Mountains and pours into Persian Gulf north of Qeshm Island.
Minab River starts from the eastern parts of Darab mountains and pours into Persian Gulf north of Hormoz Strait. Beside the above rivers several small rivers originating from Makran and Baluchestan namely Jagin. Sadooieh, etc. pass through salty marshes and are briny. The only deep river in this group is Sarbaz River which originates from Bampour and pours into Guatr Gulf. Nahang River, part of which forms the borderline between Iran and Pakistan, changes name to Rooddasht and pours into Guatr Gulf.
Hirmand River originates from Baba Mountain in Afghanistan and has a length of approximately 1,100 km and the important branch of it is called Andab. Almost the whole length of Hirmand River is located in Afghanistan and only a small part of it at south flows in Iran. In Iran this river irrigates the Sistan Plain and pours into Hamoon Lake.
This river also originates from Baba Mountain in Afghanistan. After irrigating Harat it flows to north and forms part of the borderline between Iran and Afghanistan. Its southern branch, known as Tajan, flows to Kharazm Plain. The most important branches of Harirud River in Iran are Kashfrud and Jam rivers.
This river originates from Kermanshah and Kurdistan. It joins Tigris River southeast of Baghdad. That portion of Dialeh which flows in Iran is called Sirvan River.
Located northwest of Iran. This river is formed of several streams originating from the mountains south of Urmia Lake and Uramanat region. With a length of approximately 40 km Zabsaghir Riser flows towards southwest and joins Tigris River in Iraq This river was called ‘Kaoros’ by the Greek historians.