Water (shui) is one of the Wu Xing, the five phases of Chinese cosmology. It is the phase of descent, cold, and inward stillness, associated in the classical correspondences with the direction north, the colour black, the season of winter, the emotion of fear, and the salty taste. In the generating cycle (sheng) Water produces Wood, nourishing the growing plant; in the controlling cycle (ke) Water restrains Fire, quenching the flame. These cycles of mutual generation and control order the relations among the five phases and underlie their use in Chinese medicine, the almanac, feng shui, and fate calculation. These are the conventions of the Chinese cosmological tradition, in which the five phases, Wood, Fire, Earth, Metal, and Water, turn through their generating and controlling relations to account for the movement and balance of all things.
Water closes the generating cycle (Sheng), condensing from Metal and in turn nourishing Wood, so that the sequence Wood, Fire, Earth, Metal, Water returns to its start; in the controlling cycle (Ke) Water quenches Fire, while Earth controls Water by damming it. The Huangdi Neijing correlates Water with the kidneys and bladder, the salty taste, the colour black or deep blue, the direction north, and winter, and treats it as the phase of storage, stillness and the reserve of vital essence (jing) on which the other phases are said to draw. In four pillars (BaZi) astrology a chart dominated by Water is read as adaptable and reflective but at risk of dispersal or fear without the containment given by Earth.
Sources Science and Civilisation in China, Volume 2: History of Scientific ThoughtJoseph Needham with Huangdi Neijing (The Yellow Emperor's Inner Classic)Traditionally attributed to Huangdi; actual authorship unknown, Chinese Mathematical Astrology: Reaching Out to the StarsHo Peng Yoke