[OSM-talk] waterways through water bodies

[Minh Nguyen]

Vào lúc 08:31 2021-06-22, Mike Thompson đã viết:
> I was reviewing recent changes in my area, and I came upon this:
> https://www.openstreetmap.org/way/956078735 
> <https://www.openstreetmap.org/way/956078735>
> 
> If there is a waterbody (natural=water + water=lake or pond), and a 
> stream or river (waterway=river or stream) flows into and out of that 
> body of water, should the waterway be continued through the body of water?

It's common for a waterway=river to represent the river's main channel 
or, more specifically, the thalweg. Especially if a river passes through 
a reservoir, the dammed-up river's original course is still present, 
just obscured. It isn't purely historical information: after all, in the 
Western U.S., many reservoirs will shrink this summer to the point of 
resembling their original streams. The USGS topographic layer often 
shows the precise course through a large reservoir, but an approximation 
should be fine otherwise.

> If yes, should the portion of the waterway that is inside the body of 
> water have additional tagging indicating this fact?

Pedantically, a river that's generally boat=no could turn into boat=yes 
within a reservoir. For example, [1] runs through a reservoir that has a 
public slipway and hosts rowing competitions, though I don't think 
anyone cares to follow the original river's course in particular. The 
river's course mainly matters because township boundaries are defined in 
terms of it.

[1] https://www.openstreetmap.org/way/26742829#map=14/39.0246/-84.1225

-- 
minh at nguyen.cincinnati.oh.us