Trou du Toro - "Hole of the Bull" or Forau d'Aiguallut

The next part of my hike was inspired by the book of the Frenchman Norbert Casteret, “Ten Years Under the Earth” (1940).  In this he describes his journey over four years in finding the true source of the river Garonne that reaches the Atlantic after feeding the vineyards of Bordeux. He knew that the waters from the Esera valley disappeared  in the Trou du Toro (meaning “Hole of the Bull” but marked on the Spanish maps as Forau d'Aiguallut) and that this water could emerge anywhere in such a complex geology and chaotic maze of streams and sink holes. Casteret couldn’t do what came natural to him and lower himself into the cave system because the waters go down through a bed of shifting sands. He considered dye tracer tests too expensive so he spent weeks exploring fissures and caves in the region of the Maladeta Massive.  There was also a possibility that the waters from the Trou de Toro changed valley, basin and slope, passing under a ridge of the Pyrenees and rising at the Goueil de Joueou  (meaning “Jupiter’s Eye", Uelhs de Joeu on Spanish maps) near the Cirque d’Artiga de Lin in the Val d’Aran. So for this reason, Casteret transferred his attention to the Cirque d’Artiga de Lin above the Goueil de Joueou. This is a very steep amphitheatre scored with ravines, lakes and fissures and he recounts that this was the most strenuous of his four years exploration. So it was that by the end of 1930 he knew that the disappearing waters did not reappear in the Esera valley, and that the source of the waters pouring from  the Goueil de Joueou was not from the high Cirque d’Artiga Lin.

View south-east of the Valleta de l'Escaleta with Coth des Aranesi. The cascade and Trou de Toro are around to the left.

There is also an additional angle to this story in what now-days would be called an “environmental impact” in that the Spanish authorities were planning to divert the waters of the Trou de Toro to a power plant in the Esera valley and as they thought this water eventually found itself back into the Rio Esera, they saw no problems in their plan. Casteret thought otherwise and in his own words “I trembled for the Garonne” as the waters from Jupiter’s Eye contributed about half of the Garonne as it entered France.

The cascade (the same mentioned by Casteret) above the Trou de Toro. The water from the cascade disappear a few metres downstream.

The "Trou de Toro" (Forau d'Aiguallut) where the river disappears into the sand and limestone passages.

The re-emergence "The Eye of Jupiter", Uelhs de Joeu where the waters from the Trou de Toro, having found a way under the mountains, come out of the rock in the forest floor.

In July 1931 Casteret, having got the backing several eminent scientists, started a dye tracer test by pouring fluorescein dye into the Trou de Toro. His party consisted of his wife, mother and two friends of theirs together with a Spanish muleteer. They’d crossed from Luchon (by the Port de Venasque). At twilight they cast the dye into the cascade (see photo) above the sinkhole (the dye is sensitive to sunlight and hence their delay) and found a cabin down the valley to spend the night. Early in the morning the two groups went their separate ways: the Esera detachment, his wife and two friends, and the Garonne detachment, himself with his mother. The Casterets met bad weather on the Collado de Toro on their route over the mountain ridge. In his words “the steep northern slopes of this pass, which dominates the Cirque d’Artiga Lin, demand close attention to business from climbers”. He describes it as a “ticklish matter” in thick fog! He had to navigate the plain of the Artiga de Lin by compass although he had crossed it numerous times in his researches in good weather. The account ends happily as, whilst his mother was tending to a fire in a shepherd’s hut, he found the Goueil and to his amazement it was green, the Garonne did rise in the Maladeta and in his words “…my head whirled with memories”. The story goes on because he had to escape the French police (even in those days green rivers weren't acceptable) and find his wife and friends in the Esera valley(they found no evidence of green waters!) and after much work they stopped the power project in the Esera valley.

Looking back to the Collado de Toro and lake with the Maladeta Massive glaciers in the background, a very beautiful area.

Thankfully my journey was easier in that it didn’t involve dyes, mules, bad weather or the French Police. It started after crossing the Rencluse ridge and descending into the Pilan d'Aiguallut where I found the cascade mentioned by Casteret. and the Trou de Toro, amazing sights in the autumn sunshine. I did manage to get my feet wet crossing the various streams before heading along the north side of the plain to start the ascent to the Collado de Toro. This was a really great walk passing sink holes and the occasional Wheatears to reach the ascent to the pass and lake (Ibon de Coll de Toro). After crossing a small boulder field at the lakeside, I was soon resting looking down on the Artiga de Lin valley and having a lunch which the refuge had supplied.

The largely unmarked descent down the Cirque was steep and at a couple of places involved handholds on steel cables pegged into the sides of a narrow gully. It was certainly good to reach the bottom of the Cirque with the remnants of a snow field and a very picturesque scene of shrubs and wild flowers in bloom. A short walk across the plain led me to a closed unmanned refuge and visitor centre and a short walk into the forest, a mountain cabin (cabane dera Artiga de Lin)  where I set-up for the night. In the morning, I followed the Val de Lin to reach the Delhs de Joeu and see the re-emergence of the waters from the Trou de Toro. This is now a tourist attraction complete with a paved road from Las Bordes and its own car park. Even at relatively “low water” the emergence was impressive so it is hard to imagine what it sounds and looks like with the melt waters from Maladeta peaks in full flow.

The Cirque d'Artiga de Lin in the morning light. The route down follows the gorge on the left, descending to what remains of the winter's snow.

One of the steel cables to assist the descent down the face of the Cirque. I doubt Casteret had such aides available although he may have used ropes.

There had been extensive flooding in the Val de Lin with large boulders sitting on what remained of bridges and much erosion of the river banks and forest. In June, a combination of storms and snowmelt produced widespread floods across the Pyrenees including Cauterets, Lourdes and Luchon.

After this I made my way to the village of  Las Bordes and onto Vielha (the capital town of the Val d'Aran) to catch the "Parc Bus" to Erill la Vall in the Vall de Boi, the southern entrance to the Aiguestortes National Park.