Severe, recurrent flooding of the Little Zab River to northeastern Iraq was formerly commonplace. The rate of flow in this river as it passes through the Dukan gorge is about 34 cubic yards (26 cu m) per minute during the dry season, rising to more than 4,000 cubic yards (3,000 cu m) per minutes at flood time. Iraq's Development Board was already considering major flood control, drainage, and irrigation schemes throughout the country when the Little Zab gave rise to a series of major floods in 1941, 1946, 1949, 1953, and 1954. The highest flood levels were recorded in this latest year when the river's rate of flow reached 4,800 cubic yards (3,660 cu m) per minute despite a normal average daily rainfall.
In 1954, to control further flooding of the Little Zab and to provide water for irrigation in northeastern Iraq, the Development Board awarded a contract to a French consortium for the construction of an arch dam at Dukan gorge on the Little Zab, some 37 miles (60 km) northwest of Sulaymaniya and 60 miles (100 km) northeast of Kirkuk. Between 1,000 and 1,200 families, representing the population of some fifty villages in the adjacent region, were moved and settled to the northwest at Sanga Sir. The Dukan dam and reservoir were completed in 1959 although structural problems necessitated ongoing repairs and further expense. As part of the Dukan project, a series of regulators and dams were built on the Little Zab and adjacent Udayn River, while a spillway conveying water from the Little Zab to the Udayn provided irrigation to the Ghurfa lands and the lands on the right bank of the Udayn River.
The project was tested almost immediately when the Little Zab flooded in 1959, depositing over 2.6 billion cubic yards (2 billion cu m) of water into the reservoir. This allowed a constant runoff for irrigation during the dry season from August to November. Over 20 billion cubic yards (15 billion cu m) of water were processed through the reservoir during the first six years of its operation.
The dam itself is an enormous structure, 382 feet (116.5 m) high and 1,180 feet (360 m) long. It is 20 feet (6.2 m) wide at the top and 107 feet (32.5 m) wide at its base. The reservoir behind it, covering an area of some 104 square miles (270 sq km) or more, has an estimated usual capacity of 8.9 billion cubic yards (6.8 billion cu m), but a maximum capacity of 10.9 billion cubic yards (8.3 billion cu m). The complex serves multiple purposes including flood control, the provision of hydroelectric power (originally rated at 200,000 kilowatts), and the storage of water for lean periods when the Tigris is low. Indeed, the water contained in the reservoir is intended chiefly for the Kirkuk irrigation project whereby over 890,000 acres (360,000 ha) of land around Irbil, Kirkuk, and Diyala districts are to be brought under cultivation, almost 494,000 acres (200,000 ha) around Kirkuk alone.
See also Iraq; Kirkuk; Sulaymaniya; Zab Rivers.
Ali, Hassan Mohammad. Land Reclamation and Settlement in Iraq. Baghdad: Baghdad Printing Press, 1955.
Salter, Arthur. The Development of Iraq: A Plan of Action. London, 1955.