Getting watershed from OpenStreetMap

You'd have to infer watershed data - it's not something stored in OSM normally.

Rivers and streams are directional in OSM - the direction of the ways should be downstream, and they join other streams on the way to their destination (usually the sea). You can therefore work out where watersheds are by looking at which streams and rivers are connected indirectly to which seas, and drawing the watershed between them.

A few rivers like River Ob have watersheds in super-relations, but for most rivers there are not any data.

To find out a watershed, you need to get all ways of the relation of the primary outflow river. Then search for nodes with intersections with that river. Get the river up to the source then you will get the final data for a watershed.

By the way, watersheds are usually clearly visible in the cycling map as it is just the ridge of a mountain, except for some borders like the one between the Dnieper and the Don, which are both located on the Eastern European Plain.

http://www.openstreetmap.org/relation/2086905 http://www.openstreetmap.org/relation/416351

These contours should help http://www.opendem.info/download_contours.html

Hi, have a look at the plateau de Langres, with 5 France rivers flowing in all directions its a water shed or simple a good water source for rivers. Like the Marne & Seine go west, La Saone goes south, Meuse and Meurthe go north. but no sign of a water shed on the standard OSM map.