How was Hansbach stream formed?

The Hansbach stream was formed when Hans broke through the rock with a crowbar under an area in which they could hear running water.

At the end of what appeared an age, Hans had made a hole which enabled his crowbar to enter two feet into the solid rock. He had been at work exactly an hour. It appeared a dozen. I was getting wild with impatience. My uncle began to think of using more violent measures. I had the greatest difficulty in checking him. He had indeed just got hold of his crowbar when a loud and welcome hiss was heard. Then a stream, or rather jet, of water burst through the wall and came out with such force as to hit the opposite side!