For those who’d like to untangle this, a river entering the sea at Livorno with sum connected waterways of 28,276 km, nr 2 shows 12,560 km and feeds off the same area. (just a short swim looking at 2,626,228 km where the River Rhine enters the North Sea. :o)))
Awesome tool you’ve built! I can’t seem to get the links that should include natural=water in the network to work… Eg. WaterwayMap.org - OSM River Basins does not seem to (automatically) connect the Cogburn Creek as your post indicates… Should I do more than click the link? Or is that feature no longer available?
Thanks!
Sorry about that. I turned off the natural=water connection ~6 months ago. A lot of natural=water in OSM are mapped with relations, which this tool osm-lump-ways doesn’t support. Rather than have something that is broken for half the water areas in OSM. I turned it off. Although in the area you descibe, there are ways with natural=water.
I would like to support that at some point.
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That’s not the correct way to map it though – ways with waterway=river should come first, and the surrounding natural=water areas only after that (if ever).
Not sure what is the referent of “that” but I don’t think it would be a good idea.
@Duja and @amapanda_ᚐᚋᚐᚅᚇᚐ , sorry for opening that can of worms 
I chose that particular river simply because it was used as an example in the post first describing the feature.
It seems clear that there are differing opinions on how to best map water flowing through extended bodies of water. For me, having the tool visualize connected water systems for all unambiguous mapping methods would be useful.
I guess the question is whether the tool is for detecting “wrongly” mapped water systems, or for visualizing water systems. Maybe it could even do both 
At one point, I also grouped ways based on natural=water. But my tool osm-lump-ways can’t do relations. So half the examples didn’t work. I turned that feature off.
I like connected waterways. IMO WWMorg should show both, to prevent people “mapping for the waterwaymap” 
. (BTW: OSM forum discussion on mapping through .)
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What do you mean? Do you want something fixed?
My post last sentence ended in :o))). Think you could not possibly do anything with any of the 3 cited waterway groups, just an open call to the mapping community to figure out where things need separation. The 2626228(km) number shown on the map at Rotterdam also shows up on the map near Rimini suggesting there’s a way across the Alps, maybe around.
@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.