Sometimes waterway maps include calculated flowlines. These are algorithmically derived from digital elevation data and more accurately represent where water would flow were there water flowing. That's really important not just for New Mexico arroyos but for most of the surface of the earth; there are a lot more flowlines than perennial streams.

I don't know the provenance of this data though. It's pretty spotty, I don't think someone just imported the NHD flowlines dataset or something.