Sefid-Rud

Other names and transcriptions include Sepīd-Rūd, Sefidrud, Sefidrood, Sepidrood, and Sepidrud. Above Manjil, "Long Red River".

William Smith equated the river with the Amardus (Ancient Greek: Ἀμάρδος) or Mardus (Μάρδος) river of antiquity.

The river is historically famous for its abundant fish, especially the Caspian trout, Salmo trutta caspius.

The Sefid-Rud has cut a water gap through the Alborz mountain range, the Manjil gap, capturing its two headwater tributaries, the Qizil Üzan and Shahrood rivers. It then widens the valley between the Talesh Hills and the main Alborz range. The gap provides a major route between Tehran and Gīlān Province with its Caspian lowlands.

In the wide valley before the Sefid-Rud enters the Caspian Sea, a number of transportation and irrigation canals have been cut; the two biggest are the Khomam and the Now.

Dam and reservoir

The Sefid-Rud was dammed in 1962 by the Shahbanu Farah Dam (later renamed Manjil Dam), which created a 1.86 cubic kilometres (0.45 cu mi) reservoir and allowed the irrigation of an additional 2,380 km² (919 sq mi). The reservoir mediates some flooding and significantly increased rice production in the Sefid Rud delta. The hydroelectric component of the dam generates 87,000 kilowatts. The completion of the dam had a negative impact on the river's fisheries, through reduced stream flow (due to diversion), increased water temperature, and decreased food availability, especially for sturgeon but also for the Caspian trout.

The river was known in antiquity as Mardos (Greek: Μαρδος; Latin: Mardus) and Amardos (Greek: Αμαρδος; Latin: Amardus). In the Hellenistic period, the north side of the Sefid (then Mardus) was occupied by the Cadusii mountain tribe .

David Rohl proposes identification of Sefid-Rud with the Biblical Pishon river.