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How can I tag a waterway which is used both for irrigation and for drainage?

In taginfo I see few cases (only three) of waterway=canal;drain, but it's the correct way to act?

Here in Emilia we have a large, complex and versatile system of canals for irrigation (mostly in summer) and for drainage (mostly in winter) so this situation is very common.

asked 31 Jul '14, 07:51

NonnEmilia's gravatar image

accept rate: 0%

It's better not to use a semi-colon (;) separator in the value tag of waterways, see

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answered 31 Jul '14, 13:24

ligfietser's gravatar image

accept rate: 11%


And this is also correct, but in this case it's wrong to create two ways and likewise choose a primary purpose. Those canals do exactly two things.

But I understand the "semicolon problem". Should be more correct something like this?


or, taking inspiration by service:bicycle something like this:

(31 Jul '14, 13:38) NonnEmilia

That would be better, waterway=drain is used for minor artificial waterways, canal is used for bigger waterways. Imho you can't use both at the same time, but of course the canal's purpose can be a drainage of some area.

(01 Aug '14, 09:17) ligfietser

We should keep in mind that if the structure serves dual important purposes, as is clearly the case here (to me anyway), then it should be tagged as such. I don't think it is being suggested by anyone here, but we should bear in mind not to tag for the renderer. The high integrity of the data serves us well for many many varied purposes.

(01 Aug '14, 11:13) nevw

I think a waterway which is used both for irrigation and for drainage is well described by waterway=canal;drain
Key:waterway notes that a canal is an artificial open waterway used for transportation, waterpower, or irrigation. (my emphasis)

Regional differences seem to cloud the issue as many consider that a canal implies being navigable by boats, though where live this would not necessarily be implied for a canal.

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answered 31 Jul '14, 08:49

nevw's gravatar image

accept rate: 9%


Therefore, for completeness, I could use waterway=canal;drain along with service=irrigation.

(31 Jul '14, 09:46) NonnEmilia

even more excellent :)

(31 Jul '14, 10:09) nevw

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question asked: 31 Jul '14, 07:51

question was seen: 7,886 times

last updated: 01 Aug '14, 11:13

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum