[Tagging] Rivers classification

[Daniel Koć]

I was thinking about better rendering rivers on medium and low zoom 
levels of osm-carto and I've found that we lack any classification of 
them - anything bigger than stream is just a river.

There are no suitable tags defined:

https://wiki.openstreetmap.org/wiki/Tag:waterway%3Driver

and no such tags in database too:

https://taginfo.openstreetmap.org/tags/waterway=river#combinations

There are some waterway classification systems used in cartography:

https://en.wikipedia.org/wiki/Stream_order#Usage

but how should we tag them?

-- 
"Like a halo in reverse" [M. Gore]