Subfield "Z" giddiness

Because I'll be at Special Olympics basketball practice tonight, I'll have to post early, and be brief. First, you'll note, or maybe not even notice, Dear Reader, that I began with the causal "because" and not the temporal, sloppy "since." Proof only that I read James Kilpatrick's recent columns, and haven't forgotten the lessons they contained, as of this moment. I was creating some original bibliographic records today. At work. They were records of hearings before the Oregon State Water Resources Board. The easy, efficient thing to do was to derive each successive record from the previous one. Edit dates, pagination, river names, and geographic subdivisions of subject headings. That's all. Easy. Really. Well there was one record of a hearing that covered both the Malheur River and the Owyhee River. I checked the authority records for both geographic entities. "Malheur River Watershed (Or.)" and "Owyhee River Watershed." No parenthetical state designation. I went with it. The first subject heading would be "Water resources development|zOregon|zMalheur River Watershed." The second, simply "Water resources development|zOwyhee River Watershed." I checked them. They were, they are both correct. But why? I couldn't let go. I had to know. Or die a spiritual death trying to find out. I went to the The Subject Guy and asked. Without any pause for reflection upon my query, he answered. Since the Owyhee River flows through three states, it is subdivided directly. I understood. Clearly. All I could say was "Cool." Geographic subdivision is so much more fun than mathematical long division. But that goes without saying. Doesn't it, Dear Reader?