The origin and development of human civilization are closely related to rivers. Over 90 percent of the human settlements in Bulgaria are located in the vicinity of a river. This may be why the word “river” evokes positive emotions and associations of things pure, clean, and calm. At the same time, being so close to human activities, rivers are subject to various and quite often negative impacts. For most people, a river means water flowing from the mountains to the sea. However, flowing water is only one (essential) component of the living body called “river”.