[Hygienic quality of lakes which are used as open-air bath. I. Communication: seasonal variation of total colony count, the number of Escherichia coli and coliforms (author's transl)].

Four lakes situated in the recultivated area of the Rhenish brown-coal district were examined bacteriologically during a period of one year. Total colony count and the number of Escherichia coli and coliforms were determined and compared with the influence of meteorological factors and human and animal impacts.