Waterway relations

The waterway=river tag is used in OSM on ways that make up a river. Like many things in OSM, an actual river will almost certainly be split up into many individual ways. Luckily there is a waterway relation. You can create one relation for each actual river, and then add all the ways that make up the river into that relation. Data consumers can then easily work with one object for a river and reason about it. (e.g. How long is it? What countries is this river in? What other rivers flow into it?)

Using Overpass to find missing waterway relations

Adding rivers to the relation is easy enough. But how do you know how to find them? Overpass Turbo can be used for that.

This overpass query will show you all the rivers in a bbox which are candidates for a waterway relation:

[out:json][timeout:250];
(
  // all ways that are tagged river, and have a name
  way["waterway"~"(river|stream)"]["name"~"."]({{bbox}});
  -
  // minus all the ways that are in a relation
  ( relation["type"="waterway"]({{bbox}}) ; > );
);
// print results
out body;
>;
out skel qt; 

It find all ways with the waterway=river or waterway=stream tag, that also have a name tag, and it excludes all ways that are already in a type=waterway relation.

Loading into JOSM

When you have run that query in Overpass Turbo, you can export the result to JOSM using the remote control feature of JOSM.

However JOSM has a very useful “Download from Overpass API” feature for loading data direct into JOSM, if you want to avoid your browser having to load and display a massive amount of data. However you must use a slightly different overpass format. Instead of {{bbox}} use bbox. This is the query you need for JOSM:

(
  // all ways that are tagged river, and have a name
  way["waterway"~"river|stream"]["name"~"."](bbox);
  -
  // minus all the ways that are in a relation
  ( relation["type"="waterway"](bbox) ; > );
);
// print results
out meta;
>;
out meta;

Examples

Some examples of waterway relations:

• River Liffey in Dublin
• River Shannon in Ireland