@amapanda_ᚐᚋᚐᚅᚇᚐ Any issues with the update? I can’t see it’s updated since 9:th of April.
And thanks for a good tool!
Unit is km, so the connection not straight, perhaps some circles around the moon (384.400 km away from Earth)?
There is nothing wrong with grouping rivers or bodies of water because they are in someway related. That grouping should not imply whether or how they are connected. There needs to be some type of connecting water feature. Water has to move from point to point even if it might be underground.
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Hi @IanH, I did not mean to discourage or scold any “grouping rivers or bodies of water” or any mapping practice with my posts… Did they come across like that? Maybe I simply do not understand your comment?
whoops sorry. Fixed now. 
The number on the blob is the total length of all the waterways that are connected. This can easily be very long. Imagine 2 rivers near each other that join. The total length will be longer.
Big thanks to @Mxdanger for a pretty substation improvement to the UI. It now uses a Bootstrap layout, inspired by OSM.org. This is much nicer than my hand rolled former version.
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But seven (7) times the distance Earth - Moon? Or 65 times the length of the Equator?
That’s fractals for ya! you can nest a lot of length into an area.
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I see, the number accounts for everything that is connected to the river Po. Can I place a filter to only see what is in? The Danube number reads 2,635,389 (Po 2,626,228) and the area should be much larger, especially, as the Rhein-Main-Donau-Channel obviously taken into account? – Emilia Romagna, Veneto and Lombardy more thightly knit 
Irrigation for vegetables and rice?
Agri, risotto rice. Kind of makes these numbers salt ridden if drains ditches, swales and furrows are added in.
I don’t think there’s currently a way to filter the map down to show just own “basin”. I’ve been eyeballing it based off of the coloring which fails in a few corner cases when 2 clusters end up with the same color and next to one another. Because colors are randomly assigned, flipping through the number of colors can tease these things apart a bit.
I see, the “basins” are actually colour coded. I did not realize though, because most of Europe is a single “basin”, from France to Ural, from North Sea and Baltikum to Mediterranean.
That’s because of artificial canals that connect the major basins. It’s sufficient to have a small ditch that somehow connects small waterways from different huge basins to get them merged. This ditch may exist by error, or may indeed be a true waterway. For example, this tunnel under the Alps feeds a hydroelectric reservoir Lai da(d) Ova Spin from the Inn river.
If you turn on the “Natural Waterways” option in the Settings, that results are more logical, but then that introduces a different set of problems: many natural waterways have been regulated or redirected using canals, so this option may split basins that are actually contiguous.
We would like to have a method to detect the “bifurcations” from point 1, i.e. waterways that actually connect two basins and possibly tag them somehow. However, doing that is surprisingly difficult for large basins, either by our eyes or programatically.
@amapanda_ᚐᚋᚐᚅᚇᚐ it would help a lot if we had a much larger number of colors available (say, 24), and somehow draw Artificial waterways (a different line style?) even if “Natural Waterways” option is selected… I donć’t know.
You can’t directly filter on an object, but you can adjust the length filter to only include one. e.g. “Show all waterway groups between 2,635,616 km and 2,635,618 km” link. This might not work tomorrow as people map.
The tag combinations for each map view are in the Makefile here on github. It uses osm-lump-ways, so look at the -f or -F arguments for each map view, and consult the documentation on what they mean.
Yes. Initially, I excluded waterway=canal, but had to include waterway=canal,lock=yes. The current tag rules for flowing water (used for the loops & ends, and now the Natural Waterways map is pretty powerful, but can be improved.
If you see a break that you think should be connected (& the OSM tagging is good), please open a github issue.
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I think the difference in length comes just from different times of data. Three quarters of Europe are connected somehow, and it is not here
where the Danube connects with the Po. The tunnel connects the Inn with the Inn.
Did you ever explore using a height model to find flow direction? That might help spot actual “basins” and perhaps also where locks (Schleusen in German) are missing in channels…
PS: No use for height model, way direction already does that.
I don’t know, and it’s hard to find out. I linked that tunnel just as an illustration that long canals do exist over (or under) the Alps, and one of those may indeed be the “bifurcation” between the Danube and the Po, but we haven’t found the culprit yet.
This seemingly innocuous drain links the Po to the Rhone - Way: 435393175 | OpenStreetMap
Curiously, lots of pressurized pipelines appear in the “natural” plane - WaterwayMap.org - OSM River Basins
More about the area - Hydroelectricity: the energy produced in Haute Maurienne
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Thanks for putting your teeth in… the cited drain is upstream not connected from the little intermittent area when looking in tracetrack topo, the underground way (white) from the big dam seemingly going nowhere, at least I don’t see a continuation.
The style does not show pipelines, therefore the gap. Knowing where to look its easy to find links This pipeline Way: Überleitungsstollen Bieltalbach (781351380) | OpenStreetMap links the Rhine to the Danube WaterwayMap.org - OSM River Basins - I’d have tagged a waterway=pressurized usage=headrace there - which would have connected them even on the non-artificial plane. There certainly are more links (Rhein-Main-Donau-Kanal eg.)
Apparently WIP, the 2626228 became 2635707 a week on now Rhein and Danube showing the same number.
Done. patch here for those interested.
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