Together with the rivers Karkheh (the ancient Choaspes) and Karun (Pasitigris), the Dez (Eulaeus) brings water (and sediments) from the Zagros mountains to the alluvial plain of Khuzestan (Elam). The river passes along Susa and Chogha Zanbil, and finally empties itself in the Karun, just north of modern Ahvaz. Like the two other streams, it is a slow, river; its mud makes Khuzestan one of the most fertile areas of modern Iran.