http://jglobal.jst.go.jp/public/20090422/200902034180210990

As there does not seem to be a set translation for this, and the text does not seem to be overly technical, I would probably opt for something more reader-friendly than semi-mountainous, etc. Looking at the context, I think "rural" would fit well - whether urban or rural, from urban to rural, etc.

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Note added at 2 days2 hrs (2012-07-13 17:48:05 GMT)
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To clarify, and to address comments (the character limit for replies is quite small), I am aware that 中山間地域 is translated as "Hilly and Mountainous Areas" within the scope of the 食料・農業・農村基本法. That said, I don't think this text calls for such a translation.

I think it is important to consider the context and intended meaning/writing style, and I think that the author used this term to create contrast with 都市部. I don't think that using the term chosen for use in the translation of a law in all contexts other than literary is the job of a translator. We are more than dictionaries, and real people in the real world use terms in ways that may not match up perfectly with the dictionary/proper meanings of those words.

I think that urban and rural convey this contrast well, which is why I've chosen rural. I think that perhaps Oikawa-san and Yamaguchi-san have a different (more restrictive?) image of rural than I (and probably other native speakers). It can actually be a fairly broad term. From the dictionary:

1. Living in or characteristic of farming or country life
2. Of or relating to the countryside as opposed to the city

This second definition is an image that contrasts with urban, and it is this image that I think the author intended to convey (though I may be wrong, of course). There are other ways to achieve this - e.g. in the city vs. in the country(side) - but I chose urban-rural because it is succinct and to the point, and seems to fit the text well.

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Note added at 2 days9 hrs (2012-07-14 00:46:14 GMT)
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To Yamaguchi-san:

The reason that I think that this fits with the author's intention is that I think the author wanted to show contrast, hence the ～から～まで construction. I think that the range is what is important here, more so than the legal definition of each term, and the contrasting urban-rural pair expresses that better than urban-hilly and mountainous areas. There also seems to be some correlation with the pair 水道事業－農業用水路, i.e. the urban waterworks system versus the irrigation channels or whatnot that once again reflect a rural image. It seems to me that the author wants to say that this type of power generation can be implemented close to home despite where you may be living, whether that be in the city or far from it. The source doesn't seem to me to be worried about geographical features as much as this contrast, but you do have the understanding advantage as a Japanese native, so I could be way off.

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Note added at 5 days (2012-07-16 18:22:35 GMT)
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Yamaguchi-san:

That is indeed a good point. If the author meant rural, then why not use 農村 or 田舎, etc.? Of course, we can't really know. Like you said, the author may have wanted to avoid the image associated with such words. Then again, we think about words differently as translators. Most writers will not be considering what a word would become were it to be translated. Even so, writers give careful attention to word choice, and perhaps that is why I dislike the "hilly and mountainous areas" solution - perhaps I am thinking too much like a writer and not enough like a translator, because it would make for poor writing. Even if the author wanted to focus on geographical features, I would go about it in a different way, with description, because "hilly and mountainous areas" is not a single, familiar concept in English like 中山間地域 is in Japanese. I might consider something like "whether in the city or in the mountains" if I wanted to emphasize geological features. But this is just the introduction of a magazine article, and unless I could read the full article and determine that it were of some importance later in the article, I would want to focus on good writing more than making sure that my terminology matched the translation of some law. If I had no context, I may choose "hilly and mountainous areas" to be safe, but I'm assuming JE-T has access to the full article, and within the context of what I can access online, the stilted writing that "hilly and mountainous areas" would create can be safely avoided.