Parent Water Body

This dimension names the larger body of water that a smaller one is part of, a tributary belonging to a river system, for example. Wikipedia explains that "a drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean," and that hierarchy is exactly what this dimension records. Browsing by parent water body groups tributaries and sub basins under the system they feed.