Crossing the Danube, with dry feet

What do the Amazon, Danube and Nile have in common? They all appear to have been surveyed and measured, starting at their estuaries and then working upstream. I have not researched the reason or reasons for this deviation from the norm, but maybe it was because when the first surveys were carried out, the source of all three rivers was either unknown, or, in dispute. In the case of the source of the Danube, the Roman Emperor Tiberius did some searching himself, but he appears to have given up and simply declared it to be a spring at the foot of the Black Forest escarpment, in what today is a grotto in the palace gardens of Donaueschingen.

Photo Rolf Heyne: The ’Donau Ursprung’ or real source of the Danube.
Photo Rolf Heyne: The ’Donau Ursprung’ or real source of the Danube.

This was clearly incorrect but it took until 1959 until the controversy was finally cleared up and the source of the river Breg was declared to be the real source of the Danube. Rather than attempt to rewrite history, but also to placate the furiously protesting authorities of Donaueschingen, it was decided to use some of the flexibility offered by the German language and so the ‘source’ of the Danube remained the ‘Quelle’ in Donaueschingen and its ‘origin’ or ‘Ursprung’ was assigned to the source of the Breg. Of course, due to the strange surveying starting at the estuary and working upstream, the ‘origin’ or ‘Ursprung’ is really the end! To complicate matters a little further, the small stream fed from the Tiberius source, the spring in the grotto, flows into yet another tributary river called the Brigach. The Brigach was also a candidate for being the real source of the Danube, but it was beaten by the Breg in both length and water volume. The Brigach and Breg unite about 1 kilometre downstream from where the stream enters the Brigach and for the next 2,800 kilometres or so, the name Danube is used.

My annual bike trip with Christian, Rolf and Sigi retraced the footsteps of Tiberius, but starting at the real source of the Danube and finishing in Ulm. No doubt our journey to the source was less arduous than his; we took the train to Triberg, high in the Black Forest and a mini-bus for the last 10 kilometres or so to our first stop, the Kolmenhof, at an altitude of around 1,078 m. In the garden of the Kolmenhof, the source of the Breg and real source of the Danube emerges from a ridge close to a small chapel, named after St. Martin, who also gives his name to that area of the forest. The top of the ridge forms the continental water shed, with the eastern side being drained by the Danube into the Black Sea and the western side by the Rhine into the North Sea. However, things are not always as they seem.

We set off the next morning in remarkably good shape and cycled along the top of the water shed, on a fairly good track, to an observation point called the Brend at 1,148 m. This offers views across the Rhine Valley to the Vosges Mountains and across the southern part of the Black Forest as far as the Finsterarhorn in the Berner Oberland, practically in Annette’s back yard. Unfortunately, the visibility was not too good and our view only extended to about the Rhine and the Feldberg. The next stretch was real high-speed biking, down a good road to Furtwangen, where we met up with the Breg again and continued down the granite escarpment, next to the river, to Donaueschingen. About 5 kilometres before Donaueshingen, the granite was no longer exposed and the first outcrops of Jurassic limestone became visible.

We paused long enough in Donaueschingen to visit the grotto in the palace gardens and to try the fine beer brewed by the family Fuerstenberg before continuing along the Danube, on a good cycle track, until just before the town of Immendingen. This is the first of several points where the Danube simply trickles away. A short walk along the river bank brought us to a point where the water could clearly be seen to seep away, and a little further on, the visual effects were accompanied by gurgling sounds as well. The river at this point is about 5-6 metres wide and up to 0.5 m deep, although we saw evidence that it had been much deeper, fairly recently. Another 1-2 kilometres downstream, we found a point where the river bed was completely dry and the miraculous walking across the Danube with dry feet took place. A further kilometre or so saw the river bed flooded again, albeit with noticeably less water than before. Since no tributaries flow into the river between the dry area and where the river flows again, I assume some kind of artesian-well effect forces some of the water back to the surface. This procedure is repeated several times, depending on water levels, and at some points the river bed is empty for as much 260 days each year.

The ‘disappearance’ of the water was proven in 1877, using salt and colouration. It was found to emerge again some 12 kilometres further to the south, at a point known as the ‘Aachtopf’ or Aach pot, which is Germany’s most abundant spring at around 10,000 litres a second. This is the source of the river Aach which flows into Lake Constance near the town of Radolfszell and subsequently via the Rhine into the North Sea. So much for continental water sheds.

Downstream, the town of Tuttlingen tried all kinds of tricks to stop the leakage, to no avail, so they have built a pipeline past the seepage points as a temporary solution for a continuous water supply. Since the outcropping Jurassic limestone is as porous as a Swiss cheese, eventually not even their pipeline will be a solution. It has been estimated that the underground reservoir feeding the ‘Aachtopf’ has a volume of around 50 million cubic metres, plenty of capacity to accommodate the whole volume of the river at this point.

Our journey did not include a visit to the ‘Aachtopf’, but continued along the banks of the Danube, through magnificent scenery, with limestone cliffs each side of the river. It was particularly spectacular from Muehlheim via Beuron to Gutenstein and on to Sigmaringen where we spent the second night. Since Sigmaringen is the seat of the house of Hohenzollern, we opted for a guided tour of the palace the next morning, before continuing to Blaubeuron where another pot, the ‘Blautopf’ or ‘Blue pot’, is situated. Blaubeuron is also home of a Benedikten monastery and accommodation was in great demand, because in nearby Ulm the conference of the Catholic Church was taking place. We managed to get the last four vacant beds, a forced extension of the day’s stage at this point would have meant some 4 kilometres, pushing bikes up the limestone escarpment to the plateau of the Schwaebisch Alb.

We visited the ‘Blautopf’ that evening and were lucky enough to see a diver exit the pot after an exploratory dive as part of a research programme, mapping the labyrinth that feeds the spring at a rate of around 2,000 litres a second. The pot is about 20 metres deep and gets its name from the deep blue colour which the water appears to have, it is the source of the river Blau which flows into the Danube, in Ulm. The cave has been researched to a length of around 1,500 metres, with no end in sight. The divers require three compressed air bottles to get anywhere and hopefully back again, the body language of the diver we saw returning reminded me of my reincarnation after our journey to Hades and back in the French Jura, in 2002, and that was almost dry.

The next stage of the voyage was a short, 22 kilometre trip along the Blau to the main railway station in Ulm and a direct connection to Munich. Since the weather seemed to be holding out, we decided on a debriefing in the Augustiner beer garden near to Munich’s main station, which probably took about 15 minutes too long, because I was 15 minutes from home when the water descended. We had covered around 300 kilometres in all, depending on our individual starting points, biked through some magnificent scenery, experienced some super geology and even managed to put on a kilogram or two in weight. Phenomenal!

Mike Molloy

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