Nippur was situated on both sides of the Shatt-en-Nil canal , one of the earliest courses of the Euphrates . It lies between the present bed of that river and the Tigris , almost 160 km southeast of Baghdad . Nippur was situated on both sides of the Shatt-en-Nil canal , one of the earliest courses of the Euphrates , between the present bed of that river and the Tigris , almost 160 km southeast of Baghdad .