The most important river in the center of the Iranian plateau is the Zayandeh Rud. Its source is Kuhrang in the zarkuh Bakhtiari Mountains from where it runs to the east before finally vanishing in the Gavkhuni Marshland. It is a meandering 420 km long, but from source to end covers only 270 km in a straight line.
Numerous springs and smaller rivers (Dimeh, Abzari, chamdar, Abkhorbe and na’leshkanan) join together at shurab Villag in the tange Gazi district (Gazi strait). The river at this point then becomes known as the zayandeh rud. Another branch originating at kuhrang is soon added. After tange Gazi the wasters of three further rivers (kagunag, khersanak and plaskan) contribute to the zayandeh rud. After zayandeh rud Dam lake no further additions are found.
Barrages were built to allow irrigation of farmlands wherever it was necessary. The most important of these barrages are marvan Barrage from the 9th century in Ruydasht, Allah Gholi Barrage in Jondich which dates from the Afsharid dynasty (18th century), shanzdah De Barrage built by command of the shah Suleiman the Safavid in the 17th century (the last of these is near the end of the river where it disappears into the Gavkuni Marshland). Abshar, Asiab, Goli, shakh Miyan and shakh kenar are the other notable barrages along the route.
one of the amazing bridges on the Zayandeh rud is Si-o-se-pol.
Si-o-se pol is a unique masterpiece from the era of Shah Abbas I and was built at the expense of his famous commander, Alaverdi khan (after whom the bridge is alternatively). It was built over six years (1592-1598) by the well-known master architect, Hossein Banna Esfahan. It is 295 m long and 14.75 m wide and links the upper and lower haves of chahr Bag Avenue.
On the top part of the bridge, there are two covered corridors with arched walls on both decks and on either side of the upper part, there are false arches. On the lower story, there are 25 rooms of different sizes. On the southern and northern foundations rooms have been converted into teahouses.
During the Safavid, the Abrizan or Abpashan celebrations were held at this bridge. The Safavid king would add to the grandeur of these celebrations by taking part himself. Since the Armenian Quarter of Jolfa is closed held its own khajshuyan celebrations by this bridge.