> Not sure about small rock-cut waterways  with massive impermeable sides, are 
> these ditches or canals or drains?

We don't have these in the western USA, but generally our ditches are
dug out of the soil, so I would be surprised to see a feature tagged
as waterway=ditch if it were cut from bedrock or lined with stone.

I'd think waterway=canal would be appropriate for these if they are
large enough.

One tag that's already used is canal=qanat for "a gently sloping
underground channel or tunnel constructed to lead water from the
interior of a hill to a village below", found in the Middle East

If there are small irrigation waterways that area lined with stone (or
concrete etc), we probably need a new tag, since waterway=drain is
pretty strongly associated with drainage, not irrigation, and
waterway=canal probably has a minimum width?


On 5/29/19, Martin Koppenhoefer <[email protected]> wrote:
>
>
> sent from a phone
>
>> On 29. May 2019, at 03:37, Joseph Eisenberg <[email protected]>
>> wrote:
>>
>> What, then, should be the distinguishing characteristic between
>> waterway=canal and waterway=ditch or =drain? Width or importance or
>> navigability, or should we still mention the usage as the main
>> difference?
>
>
> IIRR ditches were seen without construction like steel or concrete, just a
> man made depression to channel water, while drains are required to have
> their borders (and maybe base) constructed.
>
> Not sure about small rock-cut waterways  with massive impermeable sides, are
> these ditches or canals or drains?
>
> Stating the usage explicitly might help interpretation of the data, or while
> we’re still mapping fragments of an incomplete network, although I would
> have guessed with a more mature mapping this could already be seen from
> looking at the network structure and flow directions?
>
> What about the practical, human scale distinction we use for natural
> waterways (can be jumped over), wouldn’t it be equally interesting for man
> made waterways?
> Is a canal you can jump over still a canal, or does size somehow come into
> the equation? Can there be draining canals, or are these always drains?
>
> Cheers, Martin
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>

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