The Zayandeh starts in the
Zard-Kuh subrange of the
Zagros Mountains in
Chaharmahal and Bakhtiari Province. It flows eastward before ending in the
Gavkhouni swamp, a seasonal salt lake, southeast of
Isfahan (Esfahan) city. The Zayandeh used to have significant flow all year long, unlike many of Iran's rivers which are seasonal, but today it runs dry due to water extraction before reaching the city of Esfahan. In the early 2010s, the lower reaches of the river dried out completely after several years of seasonal dry-outs. The Zayandeh River basin has an area of , an altitude from to , an average rain fall of and a monthly average temperature of to . There are of irrigated land in the Zayandeh River basin, with water derived from the nine main
hydraulic units of the Zayandeh River, wells,
qanat and
springs in lateral valleys. Zayandeh River water gave life to the people of central Iran mainly in
Isfahan and
Yazd provinces. Before the drying-out, water diverted per person was 240 litres (63 US gallons/53
imp gallons) per day in urban areas and 150 litres (40 US gallons/33 imp gallons) per day in villages. In the 1970s, the flow of the river was estimated at per annum, or per second. ==History==