For WWM, I remove loops and cycles, and I figure basically every “only gravity” waterway only has water going downhill. I know water is often pushed uphill. But I’d like to be able to exclude them.
Just reading up on everything and catching up but as far as I understand waterway=pressurized is designed and intended for artificial conduits with no air in it, which is basically what the OSM wiki for it says (and I fully agree with it). I also noticed that the Key:waterways says this which is not the same as the waterway=pressurized tag and what I would disagree with as it’s not pressurized if its natural, it’s just without air
A waterway where water is flowing in a fully enclosed conduit and subject to pressure; this includes gravity-driven penstocks and siphons and pump-driven pipelines, for example.
For anything else natural that is sealed/has no air in it I would say siphon, we should update create a proposal for it if there is a consensus on using that for natural underground sealed waterway.
But to lay it clear what I think
- waterway=pressurized - for sealed artificial pipes only
- waterway=siphon (or similar tag) - primarily for naturally occurring sealed underground waterways
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Understood, se we definitely miss a tag to state it’s gravitational flow.
Currently it’s pretty impossible to target only pumped waterways without removing some important features that should be kept.
Given problem is siphon can be artificial too.
That’s why I still don’t understand why we should put natural/artificial distinction into waterway value instead of surrounding structure.
Why
waterway=pressurised=> artificialwaterway=siphon=> natural
could be clearer than
waterway=pressurised +
tunnel=flooded=> artificialnatural=cave(or karst or anything related to geology with holes) => natural
?
I feel reminded of highway=path: Can/May you walk there? Can/May you ride a bike there? Can/May you ride a horse there?
Certainly, making openstreetmap data hard to consume is a business opportunity 
I am not in the business of consuming openstreetmap data. I would appreciate something, that mappers can reliably tag without an engineering degree.
If we put it on the surrounding structure we need to do a lot more computational stuff to check what everything is. It’s easier if it’s already on the area
For me it’s because pressurized indicates it is intended to be pressurized. So either for pumping against gravity, to generate electricity, or other related things. But if it is not sealed and it’s powered by gravity, I don’t see why siphon wouldn’t work for natural and artificial
For what you linked I don’t see what makes it a siphon vs a pressurized pipe. To me it looks like a pipe network that just happens to go above ground there
I would be interested to learn about these natural siphons. Where do such features exist? Under what conditions do these features form?
Ok. But are there specific examples that are documented well enough that they could actually be mapped in OSM?
Water pipes are pressurised for other reasons than generating electricity, or other related things.
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I’m pretty sure the local speleo organization could help refining the way geometry, at least near the cave entrance.
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Hello
I face this argument since the very beginning.
Dedicating tags to one feature and combine them is way more consistent than mixing many concepts on the same tag.
Figures upside shows it’s not a problem to use waterway + tunnel + usage while mapping.
We are dealing here with ways only, the “surrounding structure” is carried by tunnel=* or natural=*. The only required computing is to look for the appropriate tag.
It would require to redefine waterway=pressurised, for artificial part at least to exclude siphons from it.
A global movement to reduce the cluttering of waterway=* has started years ago (and many work remains to be done), we’d better not split too much existing values as well.
Well, waterway=natural_siphon would work, even if i’m not so keen on it.
It crosses a valley and the bottom pipe is overground over the river, so it’s definitely a siphon.
See this example : File:Waterway siphon duct.JPG - OpenStreetMap Wiki
Well, waterway=natural_siphon would work, even if i’m not so keen on it.
would this really be suitable? I would think of a siphon similar to a bridge or a tunnel, it doesn’t change the way itself, like we do not have highway=bridge it could be siphon=yes (or maybe =natural/artificial?)
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I completely second that, obviously.
But the original proposal is to get rid of waterway=pressurised for natural siphons, so which waterway=* value should we use in combination with siphon=yes?
Waterway=underground_x or subterranean_x , x being river, stream would work with siphon=yes.
For what it’s worth, we have some remarkable siphons along the Colorado River Aqueduct.
This is a siphon crossing a wash at 34.0680006, -115.0330675. The wash is clearly the lowest point in the surrounding terrain, but the aqueduct siphon goes under it and resurfaces in the canal on the other side at higher elevation than the wash. (The aqueduct flows right to left in this picture.)
Edit: It seems like it might be worthwhile to make the distinction between this type of structure and penstocks or pump-driven pipelines.
On the topic of underground waterways:
I’d rather see waterway=river/stream combined with location=underground than coin new tag values to combine the two.
I wouldn’t be amazed if this would have a single value
But as long as we agree, why not. I’d like to be able to tell the ‘natural’ aspect, which is not conveyed well enougb by [quote=“Kai_Johnson, post:55, topic:115222”]
waterway=river/stream combined with location=underground
[/quote].
Sorry, edited and added a negative
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I’m going to update topic topic. Some examples been brought forward in here.
I’d consider that fine as is: A waterway=river, underground. The tunnel looks wrong to me. It is a series of caves, isn’t it?
Yes, the water infiltrates (from the knowledge available to date) from the lakes at SO, then forms an underground river (and siphon) in a cave. Part of that cave is a tourism attraction.
And yes, culvert=tunnel sound strange here. We definitely want to devise a common tagging scheme.
Unfortunately, the tagging for caves is not well established or we might have something better for this case.
There are 255 instances of natural=cave and 448 instances of tunnel=cave. And because the proposal for natural=cave never went forward, the wiki page on caves doesn’t provide clear guidance between the two.
Personally, I would prefer natural=cave over tunnel=cave because tunnel seems like something that has been constructed. And natural=cave allows us to map caves that are not tunnels.
So, the tourist part of the example above might be natural=cave with highway=footway, waterway=stream, level=-1. (Some people might prefer to tag the highway and waterway on coincident ways, but I’d prefer to combine them in this case because you’re walking in the stream.)
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