Chalchiuhtlicue's rule over the Fourth Sun and its ending in flood is not a loose detail but comes from a specific surviving text, the Leyenda de los Soles, a Nahuatl language account preserved within the colonial manuscript known as the Codex Chimalpopoca, compiled in the late sixteenth century from earlier native material. The text sets out the sequence of five world ages, each ruled by a different god and destroyed by a different catastrophe, jaguars, wind, fire, water and finally the age humanity now lives in, and it names Chalchiuhtlicue specifically as the deity presiding over the fourth of these ages, which lasted a set number of years before ending when the sky itself collapsed onto the waters and a great deluge covered the earth, its human inhabitants transformed into fish rather than killed outright, a detail that softens the catastrophe into transformation rather than pure extinction. The same text describes survivors escaping the flood inside a hollowed tree trunk, a detail some scholars compare, cautiously, to flood survival motifs found in other world mythologies without claiming any direct historical connection between them.
The Leyenda de los Soles is one of relatively few colonial Nahuatl sources that preserve a systematic native cosmogony in something closer to its own narrative voice rather than filtered primarily through a Spanish friar's commentary, which is why Chalchiuhtlicue's role in it carries particular weight for reconstructing pre-conquest belief. Her placement as ruler of the age that ends in flood also fits her double character noted elsewhere, a goddess of nourishing water who is, in the same breath, the water that can rise up and end an entire era of the world.