Khersan River is one of the branch of Karun which is originated from “Tang Sorkh” and “Kanedodehse” Mountains in 43 km south-east of Yasuj City and 15 km north-west of Ardakan Fars City. This branch continues its way with the name of “Boshar” River toward north-west. While passing through western valley of “Tang Sorkh” this river irrigates “Bardzard” and “Tang Khoshk” Rivers. It then joins “Tang Sorkh” River or “Mahmood Beigy”, one kilometer west of “Tang Sorkh” Village and then enters the valley, which is located in the middle of “Toop Abdollah” (in the east) and “Pazanan” Mountains (in the west).
In the entrance of mentioned valley it irrigates “Deh Tuly” Village and after joining another eastern river joins the water of “Dely Safadr” Valley and then “Vazag” River and flows toward “Kalgeh” Village through eastern valley of “Kharkelon” Mountain.
After passing from “Sartang” Village in 3 km distance of “Deh Sheikh” Village it joins the river of “Abza” Valley and after crossing “Deh Kohneh” and “Sarsoor” Villages, it reaches “Dorah” Village.
In the eastern part of this village, it mixes with “Gerdab” River which is passing from “Abdehi” Valley and with the name of “Garm” or “Khersan” River, enters Lordegan region in Charmahal va Bakhtiari Province. Length of Khersan River is 180 km and the height of its sources is 2900 masl.