Source of the Danube

[lethargic_man]

A few years ago, aviva_m and I visited the Danube delta in Romania.

Photo credit: Gabriela Mihail

Holidaying in the Black Forest this year, I thought it might be cool to visit the river's upper end; I don't think there's another river which I have visited both source and estuary of.

Traditionally the Danube is considered to start at the confluence of the Breg and Brigach rivers; and the source of the Danube is considered to be that of the Donaubach (Danubesbeck, to render into Northumbrian English), which is a karst spring in the castle grounds in a place called Donaueschingen.

Bar-Navi and Jane accompanied me to the spring:

...and studied its outflow:

The Donaubach flows underground after the spring, and empties, after a grand total of ninety metres, into the Brigach about a mile upstream of its confluence with the Breg to form the Danube:

Image from Wikipedia under Creative Commons licence

So that's the source of the Danube, right?

Wrong! Of course it's not! If the Donaubach is flowing into the Brigach, which joins with the Breg to form the Danube—both of which are substantial rivers by Donaueschingen—then the source of the Danube must, hydrologically, and nomenclature be damned, be the longer of those two rivers.

This, it turns out, is the Breg, which has its source about twenty-five miles upstream of the confluence with the Brigach, near a place called Furtwangen.

Wikipedia informs me that there is a rivalry between Donaueschingen and Furtwangen to be considered the source of the Danube, and that in 1981 the state government acceded to Donaueschingen's request that the source in Furtwangen should no longer be labelled Donauquelle in official maps. This is IMNSHO completely crazy; the source is clearly that in Furtwangen.

Or is it? Because I went some distance downstream, to a little downstream of the town of Immendingen, and I found the riverbed completely dry:

So what's going on here? Turns out that there's a sinkhole here (and in a couple of other places in the next few miles of the river). During the winter the river loses the majority of its water here, but during the summer half of the year, it runs completely dry, over the course of no more than a few tens of yards:

"The Danube Sinkhole" (Watch on YouTube)

The water sinks into the ground here and re-emerges in a place called Aachtopf, seven miles away, where it goes on to feed not the Danube, but the Rhine.

It turns out the Danube was only first observed to run dry in the middle of the nineteenth century, and in the first half of the twentieth century typically only did so for maybe twenty days a year, whereas today it's ten times that; so it looks like in the future the headwaters of the Danube are going to be cut off from the rest of it completely, and the longest tributary downstream from there will become the new source of the Danube.

It turns out further that the struggle between the Rhine and the Danube to capture the waters of this area has been going on a long, long time; before the last Ice Age, the Rhine was a lot shorter, and the Ur-Danube had its headwaters in the Swiss Alps near Geneva. But if things continue as they are going, it looks like the Rhine is going to have the last laugh—at least, for the next few thousand years.