I think I have some info for you. It too, is based on family lore.
My family had a large cattle ranch, El Pajarito. When the Rio Conchos was dammed, they lost a lot of land. I'm not sure if this ranch was owned by Nunez's or Portillo's. The area they are from is the Valle de Zargoza. If you surf the net for tourist info from the state of Chihuahua, you will find a picture of the dam.