intermittent stream of north-central Iraq, rising from several headstreams in the Sinjār Mountains (west of Mosul) and flowing southward to Lake Tharthār, which is a reservoir 60 miles (100 km) long. The reservoir, formerly a playa lake that varied in size with the amount of rainfall, has been connected by regulators and channels to the Sāmarrāʾ Barrage on the Tigris River, keeping it at a constant level for the purpose of flood control and storage of irrigation water.