Karkheh

Karkheh (kär`kĕ), ancient Choaspes, river, c.350 mi (560 km) long, rising in the Zagros Mts., W Iran, and flowing S into the Khuzestan lowland, where it forms a swamp bordering the Tigris River. An ancient storage dam on the river at Shush made Khuzestan one of the most prosperous agricultural regions of SW Asia until the system fell into disrepair and the irrigated area reverted to desert. The area has been reclaimed as part of the Khuzestan project.

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Karkheh 

a river in Iran whose lower course crosses into Iraq. It is 870 km long and drains an area of about 50,000 sq km. The river rises in the Zagros Mountains and, in its upper and middle course, flows mostly along the bottoms of deep gorges and sometimes through canyons. In its lower course the Karkheh flows through the Khuzistan Lowland, where it branches and disappears in the swamps of El Hawiza. During high-water periods it empties into the Tigris. High-water occurs during the spring when the snow has melted in the mountains, and there are summer floods caused by rain; the lowest water level occurs during autumn and winter. The average discharge in the lower course is about 220 cu m per sec. More than 100,000 hectares are irrigated in the Karkheh basin.