By a topographic map I'm referring to a 1/25,000 scale map, of which this is a sample French version.
French OS Maps show water sources (Referred to as source):
The German map equivalent seems to be the ATK25. Do these show water sources?
First of all, Ordnance Survey is the name of the national mapping agency in the UK and Ireland. It is a name that will not be used for other countries. Talking about an OS map outside Great Britain and Ireland is like talking about an IGN map in the UK. Nobody will understand you. Just say topographic map.
Secondly, I am not aware of a series on the scale 1:25000 or even 1:50000 covering all of Germany. There is a national mapping agency, the BKG, but they don't do scales of 1:100000 or bigger.
There are, however, mapping agencies for the different Bundesländer. I'm not German, but this far, each time I needed a German map, I was able to find a series covering the entire Bundesland. The one you linked to is the series for Bayern (Bavaria).
Now, to the point, does the series show sources? Yes. I would be surprised by a decent series on 1:25000 that doesn't. As an example, this are the Gletcherquellen (Glacier Sources) in Ramsau bei Berchtesgaden. Nothing special. Just some named source that I stumbled upon while looking for an example.
What else is shown on the maps? Well, I invite you to take a look. You can find the maps online. On that website, in the upper right corner select "Topografische Karte" in the drop down menu and zoom in on your region of interest until you see in the lower right courner "Hintergrundkarte: Topographische Karte 1:25.000". A an example, the direct link to the Gletscherquellen that I showed above.
This is for Bayern only and you were asking about Germany in general. Well, it will be similar for the other Bundesländer. In the past I've been able to locate the maps for many of them online. I can't say for sure that all of them allow you to see the maps online, but at least a big part of them do.