Great Zab
Estimates of the drainage basin of the Great Zab vary widely – from a low to a high figure of . Approximately 62 percent of the basin is located in Iraq; the remainder is in Turkey. To the south, the Great Zab basin borders on that of the Little Zab while on the east it adjoins the Tigris basin. The Zagros consists of parallel limestone folds rising to elevations of over amsl. The valleys – including that of the Great Zab – and the south-western foothill zone are filled with gravel, conglomerate, and sandstone; the result of water erosion. The Amadiya valley within the Great Zab drainage basin is the third-largest valley in the Iraqi Zagros, after the Shahrazor and the Ranya Plain.