The mining for coal, gravel, stones, etc., created holes in the landscape mostly filled up with water. In some federal countries of Germany these mining lakes are typical characteristics. Their usability depends on the water quality. Within nature-given laws there are distinct possibilities to control the quality. By research the basics for a useful water quality management are to be elaborated, generalized and transferred into recommendations for the practice. Preferably the following items are to be investigated:

·       - Influence of morphometry on stratification and trophic state

·       -  Influence oft he ground and of dumping places on water quality

·       - Mutual relationships between surface waters and groundwaters

·       -  Pass-ways of matter after filling with unsuitable river water

·       - Changing of water quality during the filling process and development to a stable state

·        - Utilizations and priorities

·        - Improvement oft he trophic state by sanitation oft he drainage basin, by treatment of filling water or by ecotechnological treatment of the lake

·        - Possibilities for neutralization of acidic lakes.