This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Water Branches gathers the two of the twelve Earthly Branches whose own fixed agent is Water: Hai the Pig and Zi the Rat, the branches that open and then crown the winter.
Hai, the twelfth branch, opens the tenth solar month at the Start of Winter and governs the hour from nine to eleven at night, in the north-northwest. It is a growth branch, storing Ren as its principal qi alongside a concealed Jia, so Hai carries the seed of the coming spring's Wood inside its own deepening Water; as the branch that opens the Wood trine, and the branch that closes the whole sexagenary round, it quietly nourishes Wood even at winter's depth. Zi, the first branch, sits at the winter solstice and governs the hour from eleven at night to one in the morning, seated due north. It is a cardinal branch, storing only Gui, so its concealed qi runs cooler and more yielding than its yang face suggests; as the cardinal Water it anchors the Water trine it forms together with Shen and Chen, and it marks the pivot in the Four Pillars where yin begins to turn back toward yang.
Between them the two Water branches trace winter's whole arc, from the seed Hai already carries toward spring to the depth of cold and dark Zi marks at the year's true turning point. Both began, like every branch, as day-count signs in the oracle-bone tradition, combined with the ten Heavenly Stems to number a sixty-day cycle long before either carried an animal at all.