Tablet II begins with more overpopulation of humans and the god Enlil sending first famine and drought at formulaic intervals of 1200 years to reduce the population. In this epic Enlil is depicted as a cruel, capricious god while Enki is depicted as a kind, helpful god, perhaps because priests of Enki were writing and copying the story. Tablet II is mostly damaged, but ends with Enlil’s decision to destroy humankind with a flood and Enki bound by an oath to keep the plan secret.
Tablet III of the Atrahasis Epic contains the flood story. This is the part that was adapted in tablet XI of the Epic of Gilgamesh. Tablet III of Atrahasis tells how the god Enki warns the hero Atrahasis (“Extremely Wise”) of Shuruppak, speaking through a reed wall (suggestive of an oracle) to dismantle his house (perhaps to provide a construction site) and build a boat to escape the flood planned by the god Enlil to destroy humankind. The boat is to have a roof “like Apsu” (a subterranean, fresh water realm presided over by the god Enki), upper and lower decks, and to be sealed with bitumen. Atrahasis boards the boat with his family and animals and seals the door. The storm and flood begin. Even the gods are afraid. In tablet III iv, lines 7-9 the words “river” and “riverbank” are used, which probably mean the Euphrates River, because Atrahasis is listed in WB-62 as a ruler of Shuruppak which was on the Euphrates River.
After seven days the flood ends and Atrahasis offers sacrifices to the gods. Enlil is furious with Enki for violating his oath. But Enki denies violating his oath and argues: “I made sure life was preserved.” Enki and Enlil agree on other means for controlling the human population.
Source: Atra-Hasis – Wikipedia