Lesson plan
Hydrological code
A hydrological code or hydrologic unit code is a sequence of numbers or letters (a geocode) that identify a hydrological unit or feature, such as a river, river reach, lake, or area like a drainage basin (also called watershed in North America) or catchment. One system, developed by Arthur Newell Strahler, known as the Strahler stream order, ranks streams based on a hierarchy of tributaries. Each segment of a stream or river within a river network is treated as a node in a tree, with the next segment downstream as its parent. When two first-order streams come together, they form a second-order stream. When two second-order streams come together, they form a third-order stream, and so on. Another example is the system of assigning IDs to watersheds devised by , known as the Pfafstetter Coding System or the Pfafstetter System. Drainage areas are delineated in a hierarchical fashion, with "level 1" watersheds at continental scales, subdivided into smaller level 2 watersheds, which are divided into level 3 watersheds, and so on. Each watershed is assigned a unique number, called a Pfafsetter Code, based on its location within the overall drainage system.
Article summary
A hydrological code or hydrologic unit code is a sequence of numbers or letters (a geocode) that identify a hydrological unit or feature, such as a river, river reach, lake, or area like a drainage basin (also called watershed in North America) or catchment. One system, developed by Arthur Newell Strahler, known as the Strahler stream order, ranks streams based on a hierarchy of tributaries. Each segment of a stream or river within a river network is treated as a node in a tree, with the next segment downstream as its parent. When two first-order streams come together, they form a second-order stream. When two second-order streams come together, they form a third-order stream, and so on. Another example is the system of assigning IDs to watersheds devised by , known as the Pfafstetter Coding System or the Pfafstetter System. Drainage areas are delineated in a hierarchical fashion, with "level 1" watersheds at continental scales, subdivided into smaller level 2 watersheds, which are divided into level 3 watersheds, and so on. Each watershed is assigned a unique number, called a Pfafsetter Code, based on its location within the overall drainage system.
Key claims
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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Key claims and bibliography are generated from the same tracked claims and sources as the article page.