Usage of “welches”

Question

I came across the following sentence:

Welches ist die zuständige Behörde?

I wondered why it is welches and not welche (using feminine for Behörde).

A quick search in Google seems to indicate that welches is correct (returns many many more results), but why?

Answer 1

Both versions are possible, but they have different nuances.

Welches ist die zuständige Behörde?

The welches here is entirely generic. It can be substituted with everything, which is especially helpful if we don’t know what we are really asking for. It’s like saying ‘I know someone is the appropriate authority, but I have no clue who they actually are.’

Welche ist die zuständige Behörde?

This is a modification of the first sentence but knowing what kind of a thing we are looking for, and implicitly expecting an answer that has feminine genus.

Welche Behörde ist zuständig?

This sounds more like ‘we have a list of possible authorities; which one should I ask?’ It sounds a tad more closed to me than the open-ended welches ist …

Essentially, all three are understood and all three are more or less equally valid. More detail can be found on canoo.net.

Answer 2

Welche would be correct here, too, though in this word ordering with a quite literary touch (and a slightly different meaning, see below). More common would be

Welche Behörde ist zuständig?

as an alternative to

Welches ist die zuständige Behörde?

I’d say, you could express the difference between the two in English by

Which agency is authorized?

vs.

Which agency is the authorized one?

So in the second expression (which for my non-native feeling is not as frequent in English as the German counterpart) you focus more on the fact that there is a finite set of agencies and you ask for the right one, while in the first it's more "open-ended".

“Welches ist die” expresses “Which is … the one”, but I’m not sure about the exact syntactic explanation for it.

Answer 3

Two possible explanations:

1. "Welches" is used in the sense of "Was". An English equivalent would be:

What is the competent agency?

Unlike in English, Germany does not make as sharp a distinction between "welches" and "was" as English makes between "which" and "what".

2. There was a sentence before that included several examples of agencies, and all of them were neuter. E.g. "Wir kennen das Ordnungsamt und das Bauamt. Welches ist die zuständige Behörde?"

(as a side note: Jurists differentiate Amt from Behörde. Everyday language does not.)