[Tagging] Proposed features - RFC 2 - Pressurized waterways

Kevin Kenny kevin.b.kenny+osm at gmail.com
Wed Feb 21 16:25:43 UTC 2018

On Wed, Feb 21, 2018 at 9:05 AM, Fran├žois Lacombe
<fl.infosreseaux at gmail.com> wrote:
> In the same time, systems like "Los Angeles Aqueduct" are called aqueduct
> and are composed of canals, tunnels and pipelines.
> https://en.wikipedia.org/wiki/Los_Angeles_Aqueduct
> That's why I like the definition of Aqueduct like a system and not like a
> precise building.
> Am I wrong ?

I think you're right. The Aqua Marcia, Aqua Ano Vetus, Aqua Anio
Novus, and Aqua Claudia were all known as 'aqueducts' and were systems
that were tens of km, in canals where possible, but mostly in
underground conduits. There were pressurized syphons for valley
crossings. Only the terminal portions of the aqueducts, as they
approached the City, or crossings of deep valleys, were on arcades -
but these make the tourist pictures, so people get the incorrect
impression that 'aqueduct' is synonymous with 'arcade'.

The arcades were used as the water approached Rome because the whole
system was gravity fed, and having the water up on a high arcade was
the way to get decent water pressure at the tap.

New York City's system runs on a similar plan, but with pressurized
tunnels. The system is entirely gravity driven from its sources in the
Catskill Mountains to the tap. The upper sources of the system are as
far away as https://www.openstreetmap.org/way/135512500 (for the
Catskill Aqueduct) and https://www.openstreetmap.org/way/134694145
(the tunnel doesn't appear to be mapped) for the Delaware Aqueduct.

Using 'canal' for https://www.openstreetmap.org/way/135512500 - when
it's a pressurized syphon - is suboptimal, but is the 'least wrong'
thing in current tagging.

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