Faecal bacteria – bacteria that are present in the digestive system of humans and animals – are known to contaminate waters. They can sometimes be a health hazard. Little research has been conducted into the spread and distribution of faecal bacteria in rivers and, above all, into their input from the surrounding landscape. Researchers from the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) and from Scotland’s University of Aberdeen have developed an indicator-based model that can be used to assess the dynamics of faecal bacteria such as E. coli on the basis of hydrological processes in the landscape and the connectivity of streams – an important basis for managing the acute or sustained microbial contamination of waters.