What does the watershed in geomantic omen mean?

Watershed refers to the mountains or highlands that separate two adjacent river basins, from which rivers flow in two opposite directions. There are many watersheds in nature, such as mountains and plateaus, but they can also be slightly undulating plains or lakes, and even some rivers become the watershed of two watersheds, and the watershed is the ridge of the watershed. It is the boundary between adjacent basins, usually the highest point of the basin. The watershed in geomantic omen refers to the geomantic effect.