Drainage basin / watershed
Overview
A drainage basin or watershed is the area of land where all surface water converges to a single outlet, such as a river, lake, or ocean. Trails often cross multiple basins along their length.
Key points
- Defines which direction precipitation and runoff ultimately flow.
- Separated from adjacent basins by ridges or high ground.
- Influences water availability, river orientation, and valley patterns.
- Understanding basins can help interpret maps and anticipate water flow.
- Large rivers may serve as basin outlets many kilometers away from the trail.
Details
Drainage basins, also known as watersheds or catchments, describe how water moves through landscapes. Precipitation that falls within a given basin tends to flow downhill through streams and rivers that eventually join a main watercourse and exit at a single point. Ridges and high ground define the boundaries between neighboring basins.
For thru hikers, awareness of drainage patterns can help make sense of how valleys align, where major rivers are likely to be encountered, and how terrain may change when crossing from one side of a continental divide to another. In some regions, basins correspond to distinct climatic or ecological zones.
On maps, identifying which direction streams flow within a basin assists with orientation and micro-navigation. It can also aid in understanding why certain sections of a route are wetter, drier, or more prone to flooding.
While detailed hydrological analysis is not usually necessary for day-to-day hiking decisions, the concept of drainage basins provides a broader framework for understanding landscape structure along a long route.
Related topics
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Illustrative hiking footage
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