Question: how did utnapishtim find out about the flood?
Answer: Utnapishtim tells Gilgamesh a secret story that begins in the old city of Shuruppak on the banks of the Euphrates River. The "great gods" Anu, Enlil, Ninurta, Ennugi, and Ea were sworn to secrecy about their plan to cause the flood. ... He asked Ea what he should say to the city elders and the population.