Sources of the coliform bacteria in the lake Bohinjsko jezero

The lake Bohinjsko jezero is the largest natural lake in Slovenia. It is 4.350 m long, 1.250 m wide and 45 m deep. Nevertheless, biological and chemical indicators show that the inflow of nutrients has been increasing in recent years as a result of tourism. Furthermore, the presence in the lake of coliform bacteria of faecal origin has been detected. In 2006, several locations along the lake shore were controlled to investigate the faecal bacterial contamination of the lake. In 2007, the research was expanded from the lake itself to the affluent of the lake, the Savica river and adjacent high-mountain lakes. The evaluation of coliform bacteria used “the most probable number” (MPN) method. The number of bacteria in water samples varied from 0 to more than 438 per 100-mL sample. The results support the conclusion that part of the faecal coliform bacterial population originates from septic tanks in houses and other dwellings, and a smaller part from pastures, meadows and fields in the lake area.