Hello,
I am currently mapping a limestone area which has a number of small streams that that start as springs and then end in a wetland area or a hole in the ground. Is there any strategy for tagging these in a way that does not generate osmose “unconnected waterway or wrong way flow” errors?
I suppose marking the end node as natural=coastline would be very bad “tagging for osmose” karma 
Roger
The validators are only alerting to possible errors that may need correcting and there are many false positives at times. So if correctly mapped and tagged that is fine.
If you want to inform other editors to the situation you could add a note= tag and a short explantion.
It won’t help with Osmose, but a note indicating that “the water disappears underground here” would help other mappers.
The most famous UK example of this that I can think of is Water Sinks near Malham such as http://www.openstreetmap.org/node/12792309, which is tagged as “waterway=cave_of_debouchement”. A web search doesn’t find that term outside of an OSM context, and the only OSM ones http://overpass-turbo.eu/s/g6D are at Malham. I don’t remember it from Geology lectures at college, but maybe I slept through more of them than Mike Collinson (who originally tagged it) did.
It might be worth checking other limestone areas in OSM to see what people have gone for.
“sink” is also used (see http://overpass-turbo.eu/s/g6E ), but at least some are sources and some not natural sinks.
Comment retracted
I have settled on tagging upstream end nodes with natural=spring and putting a note on the downstream end nodes. I am not sure that it is correct to use debouchement on a place where water disappears. As far as I remember a debouchment is describing something emerging or “coming out of the mouth”.
The place I am working on is the " Morecambe bay limestone" landscape character area.
Roger
I’d be a bit careful about tagging the upstream end as a spring. It’s quite possible in a limestone area that these are underground streams.
A good example might be Long Kin East pot on the Ingleborough plateau, where one can walk underground along the stream between two entrances (not too far or you go over the waterfall).
I’d really not worry about it: adding tags for a QA tool in the end is similar to adding them for a renderer. In KR you can switch off certain validations too.