|Location:||Kleines Walsertal. At the Naturlehrpfad Schwarzwassertal (Nature education trail).|
|Address:||Landschaftsschutz Kleinwalsertal e.V., Schwarzwassertal, 87568 Hirschegg, Tel: +49-8329-6180, Fax: +49-8329-3246. E-mail:|
|As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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The Schwarzwasserhöhle (Black Water Cave) is located at the mid part of the Schwarzwasserbach, 750m uphill from the parking and the sports field. This part is narrow and gorge-like, formed by the small river Schwarzwasserbach in the Cretaceous Schrattenkalk limestone. The water of this rivulet is coming from the southern hills, which are not formed of limestone and thus drain on the surface. The water from the nortwestern side of the valley, the Hoher Ifen and the Gottesacker drains underground to some big karst springs downhill.
The Schwarzwasserhöhle is a cave. Its entrance is rather wide but very low, and it is located in the bed of the river, to be exact in a small depression in the river bed. So in times of low water the river runs into this deression and then into the cave, vanishing completely and reappearing a few kilometers below. In this times of low water the small Aubach, a tributary which springs at the Aubachquelle, about 1km below the Schwarzwasserhöhle, reactivates the river and fills it with water. During very dry periods even this spring falls dry and the river bed keeps dry for one more kilometre.
Much different is the situation at times of high precipitation, during spring or long and heavy rains. First the cave is still able to swallow the rising amount of water. Then the capacity of the swallow hole is reached and the ponor is not able to swallow all of it. The excess water fills the small depression in front of the cave and the Schwarzwasserbach starts to run down its subsurface bed. So the cave still works as a ponor, but the river runs down its bed and the entrance to the cave is covered completely by water. At the same time the karst groundwater table rises, fed by the rain, and the level becomes higher than the location of the cave entrance. The water now flows out of the cave and it is now a karst spring, located under the river and feeding it.
When the rain or the snowmelt ends, the water table lowers and the river shrinks too. When the water tabel is below the cave entrance, it again starts to swallow, and as soon as the swallowed amount becomes as big as the water of the river the river bed below falls dry. After some more time the cave entrance becomes visible again.