- The entire region drained by a waterway or into a lake or reservoir. More specifically, a watershed is an area of land above a given point on a stream that contributes water to the streamflow at that point.
- Areas that are permanently wet or are intermittently covered with water.
- Wilderness (Wilderness Area)
- Undeveloped federal land retaining its primeval character, without permanent human habitation or improvements. It is protected and managed to preserve its natural condition. Wilderness Areas are designated by Congress. (See 'pre existing use')
- Wildland Fire
- Any non-structure fire, other than prescribed fire, that occurs in the wildland.
- Wildland urban interface (WUI)
- Areas where communities are expanding into tracitional forest and other resource lands.
- Wildlife habitat diversity
- The distribution and abundance of different plant and animal communities and species within a specific area.
- Trees uprooted by wind (See edge-effect).