The Diyala (Arabic: نهر ديالى Nahr Diyālā; Kurdish: Sîrwan; Farsi: دیاله Diyâlah, سيروان Sīrvān) is a river and tributary of the Tigris.It is formed by the confluence of the Sirwan and Tanjaro rivers in Darbandikhan Dam in the Sulaymaniyah Governorate of Northern Iraq.Navigation of the upper reaches of the Diyala is not possible because of its narrow defiles, but the river's valley provides an important trade route between Iran and Iraq.[6] In 693 BC, the Battle of Diyala River took place between the forces of the Assyrians and the Elamites of southern Iran.The river is mentioned in Herodotus's Histories under the name Gyndes, where it is stated that the king Cyrus the Great dispersed it by digging 360 channels as punishment after a sacred white horse perished there.[12][13][14] In Iraq, the river first reaches the Darbandikhan Dam which generates hydroelectric power and stores water for irrigation.