Brunnwässer are small, slow-flowing tributaries of the Lech River that are fed by hillside streams. They flow along the valley floor until they flow into the Lech without any great difference in elevation. For newts and other amphibians they represent very important spawning waters. Water birds, such as the mallard, use these valuable biotopes as nurseries and raise their chicks. Fish spawn in the quiet well waters and young fish stay here for some time before migrating to larger streams. During storms or floods, the Lech usually rolls through the valley in a very brown color - it brings a lot of suspended matter (= substances that are transported in flowing waters and kept in suspension. Grain diameter for Alpine rivers: 1 mm). In these cases, well waters are important refuges for fish, because they would suffocate in the Lech.
Bilek's azure damselfly