Is there a common tag for underground infiltrated watercourses?

According to Wikipedia, there is an underground connection (OSM) between the river “Esera” and the spring “Uelhs deth Joeu”. The water from the Esera seeps away at the “Forau d’Aigualluts” and then emerges again around 3.6 kilometres further on. The Wikipedia article can be easily read using translation tools and is very interesting.

This phenomenon connects the Garonne and Ebro rivers and creates a link between the Atlantic and the Mediterranean.

Is the used waterway=stream the correct tagging for this natural phenomenon?

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The connected watershed can be seen on, on the “Natural Waterway (excl. canals)” map view, which is aimed to be “naturally flowing waterways”. ( intro post)

The current tag filter for calculating this is: waterway∈dam,weir,lock_gate,sluice_gate,security_lock,fairway,dock,boatyard,fuel,riverbank,pond,check_dam,turning_point,water_point,safe_water→F; waterway∈ditch,drain,tidal_channel→F; waterway=canal∧lock∈yes,disused→T; waterway=spillway∧area=yes→F; waterway=canal∧usage=spillway→T; waterway=canal∧usage∈headrace,tailrace→T; waterway=canal→F; waterway→T; F using the osm-lump-ways tag filtering system¹

It’s the waterway=stream tag on w413263368 which causes these 2 watersheds to be joined.

Initially I thought it was a mapping mistake, but now I think it’s a regular river bifurcation. Changing this from waterway=stream to something else might be a good idea. But I think any map of “connected natural water flows” will have to include join the Garonne & Ebro like this. :thinking:

¹ Yes this is a new tag filtering system. :stuck_out_tongue: No, I don’t want to implemented SQL

Here’s how it is done nearby Way: ‪Orbe inférieure‬ (‪1111533314‬) | OpenStreetMap

A better tag would be needed, IMO

A generic waterway=underground until we know better on the actual course?

For basins there’s the basin=infiltration value. There’s also waterway=infiltration_area with agrand usage of 7 times. ;-)))

Just FYI

So, how about a new tag describing natural subterranean water course or flowing aquifers?
Practically the exact course is often unknown, however waterway connection is known from experience or geology.



According to this source Le problème du Trou du Toro, d'après M. Norbert Casteret (Le problème du Trou du Toro. Détermination des sources du rio Esera et de la Garonne occidentale) - Persée? the gorge is connected to the Garonne (page 120 top) but not to the Esera. Established by experiment in 1931: All the green pigment went one way only.

PS: This Way: ‪Ésera‬ (‪1214146466‬) | OpenStreetMap then should not be there at all. I placed Note: 4227245 | OpenStreetMap - The Catalan topo map has no through river there, additionally the water must flow upwards when following the OSM way; Catalan map calls upstream Riu de Barrancs too.

Meanwhile, the underground stream has been deleted achavi - Augmented OSM Change Viewer  [attic] in a quest to fix water flows network. Unfortunately, this is the one that really exists. The other connection that was left in place is the one not existing.

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IMHO there is a big difference between water flowing (both free and pipe) in a cave and aquifers percolating through ground. It shouldn’t be the same waterway value as it’s two different flowing regimes.

waterway=underground mixes too much the flow and its container, and conflicts with canals in tunnels, underground pipelines

The problem may be looking to mix too much things in a single key. It’s important to consider the flow in one hand and its container on the other to get a simpler solution.

There are also underwater waterways. Fresh water rivers under saltwater bodies.