[Tagging] Start of a river

Dave Swarthout daveswarthout at gmail.com
Mon Feb 27 01:27:46 UTC 2017

Stephan's reference to Wikipedia helps to properly define source in
this context :

Wikipedia: confluence: In geography, a confluence is the meeting of two or
more bodies of water. Also known as a conflux, it refers either to the
point where a tributary joins a larger river, (main stem), or *where two
streams meet to become the source of a river of a new name*, such as the
confluence of the Monongahela and Allegheny rivers in Pittsburgh,
Pennsylvania creating the Ohio River.

The point of confluence isn't a "source" in the normal sense (that is
usually a spring, glacier or pond)  but it does indicate the beginning of a
new named river and as such, justifies special treatment IMO. In the
situation where that beginning point is a spring the two tags one might
use, waterway=source and natural=spring, do not interfere with one another.

The other Wikipedia article about River_source favors using the source of
the named river's longest tributary as its source, so it disagrees with the
first article. In practice, an ordinary OSM user probably will not usually
be able to determine such a source point unless he or she happens to be in
the field with map and measuring tape.

I think waterway=source is a good candidate for inclusion in the OSM Wiki
but I'm not anxious to add it. Editing that blasted Wiki is so difficult I
usually avoid it at all costs. The waterway page looks easily editable so
perhaps I'll give it a try if we are all in agreement that such an
addition makes sense. The Relation:waterway page uses a table. No way I'm
going near that page LOL

I know it's difficult to find consensus on this list, or anywhere for that
matter, so I'll wait until all the comments are in before going ahead with
any change to the Wiki.



On Sun, Feb 26, 2017 at 11:04 PM, Stephan Knauss <osm at stephans-server.de>

> how about extending the waterway relation with a member role which can
> indicate either the "spring" or the "source" in case of a "creation" of a
> river by multiple tributary rivers?
> Not sure how it would best be called. Source? Origin? Confluence? Is there
> a specific hdyrology term for this?
> Wikipedia might indicate that "source" is the right word to use.
> https://en.wikipedia.org/wiki/Confluence
> https://en.wikipedia.org/wiki/River_source
> If this is also suitable for a spring, then changing the role spring to
> source would do the trick.
> https://wiki.openstreetmap.org/wiki/Relation:waterway
> While you update the wiki: I feel the "tributary" role also deserves to be
> documented in the wiki page. It is used nearly 7.000 times.
> Stephan
> On 26.02.2017 09:41, Dave Swarthout wrote:
>> That's interesting. I wonder if the tagging of tourism=attraction is
>> totally appropriate but surely a waterway=source tag is. Presumably the
>> mapper was trying to indicate that the source of that stream is where
>> that node is.
>> I'm going to start using the tag myself and let data consumers figure it
>> out if they wish. After a while I'll consider adding it to the Wiki.
>> There are a few instances of the tag in use already.
>> On Feb 26, 2017 2:23 PM, "Martin Koppenhoefer" <dieterdreist at gmail.com
>> <mailto:dieterdreist at gmail.com>> wrote:
>>     The point where it starts doesn't (yet) have any meaningful tags,
>>     just a property disguised as a
>>     feature: http://www.openstreetmap.org/node/135500355
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Dave Swarthout
Homer, Alaska
Chiang Mai, Thailand
Travel Blog at http://dswarthout.blogspot.com
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