During his trips to skating after major rivers to the lions – perhaps fortunately – did not meet much. Are not typical for the tiny streams near the springs, around which led grateful hikers winter routes. And so their scope and meaning rather underestimated.

The mistake pointed out to me the other called expert engineer Václav Matousek. Bottom ice are well seen in the heavy frosts in the steep foothill rivers, such as the otter or Pošumavská – at the other end of Bohemia – Wild eagle and UPA. The origin of ground ice and how it looks? When you freeze water surrenders heat to their surroundings and – if the temperature has reached the freezing point – the result could only be the formation of ice. In the rapidly flowing waters, but small ice crystals can not maintain the level (although they are lighter than water alone) – by eddies of turbulence across the full width and depth of flow. These crystals (which can also penetrate when it snows in the water) we denote collectively as vnitrovodní ice. Chance to stop him only offer items protruding from the bottom, especially rocks, but the smaller stones, or perhaps thresholds dams – there are growing spongy tufts of the bottom ice. On the rocky days later small islands of the bottom link to the entire ice sheets.

Ground ice I’ll probably just as disjointed thresholds over weirs or current caps on exposed sides of boulders in stream beds flowing streams and rivers. Or, if the water is clear, and it is quite often in winter, as a greenish, bluish or brownish “mushrooms” from the visible through the bottom. Closer inspection reveals that they are grown on large boulders or submerged tree trunks.

Sometimes just small changes in the weather (or do not come, just when the development of the bottom ice reaches a certain balance states) and the plates of the bottom ice “detaches” from the bottom. This causes clogging of bed, and large fluctuations in the flow – which can make further changes further downstream.