[Tagging] How to tag small canals?

Javier Sánchez Portero javiersanp at gmail.com
Fri Aug 17 11:09:38 UTC 2018

This kind of man-made structure for water transportation is very frequent
in Azores, Madeira, Canary Islands and Mediterranean countries. Please see

Now most of them are tagged with waterway=ditch.

As long as I now, they could be used not only for irrigation but also for
drinking. They could be open to air or closed, located on ground, over
(aqueduct) or inside (tunnel). Usual width from 0.2 to 1.0 meters.

El jue., 16 ago. 2018 a las 15:15, Christoph Hormann (<osm at imagico.de>)

> On Thursday 16 August 2018, SelfishSeahorse wrote:
> > Hello
> >
> > What is the usual (or sensible) way to tag small canals like mill
> > races (example: [^1]) or small irrigation channels (example: [^2]),
> > i.e. the small equivalent of waterway=canal?
> A bit of information on current meaning of artificial waterway tags:
> waterway=ditch and waterway=drain are largely used without a well
> defined difference between them.  In terms of documented meaning
> waterway=ditch is more for features collecting water while
> waterway=drain is more for features transporting water.  But this is
> not a difference you can find consistently being made in actual
> mapping.  Both tags were invented and are primarily used for waterways
> removing undesirable water.
> There is also some minor use of waterway=ditch and waterway=drain for
> smaller natural waterways because it is rendered slightly thinner than
> waterway=stream in the standard style but this is generally accepted to
> be abuse of the tags.
> waterway=canal is essentially for all open artificial waterways that are
> not primarily for transporting away undesirable water (which would be
> waterway=ditch or waterway=drain).  However since the standard style
> renders it in a fairly prominent form with a thick line smaller canals
> (like for irrigation purposes) are often tagged differently
> (waterway=ditch, waterway=drain or waterway=stream) despite not
> qualifying as such.  Still waterway=canal is the corrent tagging here,
> nothing except the standard style suggests a lower size limit for
> waterway=canal.
> All of this together has its origin in the fact that in the UK and other
> early OSM countries large artificial waterways are almost always for
> navigation and small artificial waterways are almost always for
> transporting away undesirable water.
> Long story short: My recommendation would be tagging waterway=canal and
> specifying usage=* and width=*.  This might not look ideal on the map
> but will allow all data users to correctly interpret the data.
> --
> Christoph Hormann
> http://www.imagico.de/
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