Hydrological code

A hydrological code is a sequence of numbers or letters that identify a hydrological feature like a [river], [lake], [watershed], [catchment] or [riversegment]. Several hydrological codes are existing. The code developped by [Strahler] orders catchments with respect to the number of tributaries upstream. The hydrological code of [Pfafstetter] identifies riversegments along the longest flowpath.