From the wiki: https://wiki.openstreetmap.org/wiki/Tag:waterway%3Dstream - "the commonly accepted rule for OpenStreetMap is that a stream can be jumped across by an active, able-bodied person". I would guess that around 99% (maybe 99.9%) of named waterways in Texas should actually be classed as "rivers" on OSM. In contrast, "streams" are small enough that they are not typically visible via satellite/aerial imagery, and rarely mapped as they require firsthand, in-person knowledge. 

I realize this may be counterintuitive, in part because what we refer to outside OSM as a "river" is quite different, but it is the long-established rule.