Sumerian cosmology put fresh water underneath everything. The Abzu, the deep of sweet water below the earth, was the domain of Enki, god of wisdom, craft and the ordering of the world, and his temple at Eridu stood on the water's edge; the great city temples were supplied by canal, and a god's house was expected to have water running to it. The rivers themselves carried judicial authority, since the river ordeal, in which an accused person was thrown in and vindicated by floating, appears in the law collections as a normal procedure.
The literature of the region is full of water rising against the world. The Sumerian flood story, the Atrahasis epic and the flood tablet of Gilgamesh all describe the gods deciding to destroy humanity by deluge and one man building a boat, a family of narratives from which the Genesis account is generally held to descend.
Genesis in turn names the Euphrates as the fourth river of Eden and, repeatedly, as the far boundary of the land promised to Abraham's descendants. The exile of Judah after 586 BCE was to cities on its channels, Nippur and Babylon among them, and Psalm 137 places the exiles sitting and weeping by the rivers of Babylon with their harps hung on the poplars. The Babylonian academies that produced the Talmud sat in the same country a millennium later.