[Tagging] Watershed or Drainage Basin relation draft proposal

[Christoph Hormann]

On Thursday 13 September 2018, Joseph Eisenberg wrote:
> Relations of type=watershed are currently used over 2000 times and
> there is a descriptive Wiki page but no proposal. (
> https://wiki.openstreetmap.org/wiki/Relation:watershed)
>
> It would be useful to have a relation that showed drainage divides
> (aka watersheds) and drainage basins (the network of streams and
> rivers draining into a water body or waterway)

Watershed divides are an abstract non-physical concept that is generally 
not verifiable in practical mapping - there are cases where they are 
(because they evidently coincide with physical features like ridges) 
but there are huge parts of the world where they are not and you would 
only try to estimate them based on already existing data.

In short: This is not something you can reasonably map in OSM.

-- 
Christoph Hormann
http://www.imagico.de/