Pfafstetter Coding System

[1] It is designed such that topological information is embedded in the code, which makes it easy to determine whether an event in one river basin will affect another by direct examination of their codes.

[2] In the 1950s, Pfafstetter suggested the use of a hierarchical system of coding river basins,[3] later described in a 1989 paper.

[4] The method was applied to Brazilian water networks, and has been used in a number of other applications.

In a water system to be coded, the main stem is defined as the path which drains the greatest area.

This results in four tributary basins, as well as five inter-basin regions which are drained by the main stem.

Example of Pfafstetter coding
An example of a river system coded with the Pfafstetter coding system. The main tributary water basins are coded with even numbers 2-8, and the inter-basin regions with odd numbers. The code 0 is reserved for basins unconnected to the main stem.
Example of Pfafstetter coding
Coding continues recursively, with each new digit appended to the previously obtained code