"stream" vs "river" must a matter of degree. 

I haven't seen what's on the ground here, but from my hike elsewhere on Monsanto, I think this I highly likely to be what the documentation calls a stream: 

" (the commonly accepted rule for OpenStreetMap is that a stream can be jumped across by an active, able-bodied person)." 

That's all the more so as it's intermittent: in Europe, intermittent rivers are (afaik) very rare.