Adenoviruses (AdV) are related to respiratory and gastrointestinal diseases in animals and human beings. Their wide genetic diversity in water bodies and their resistance to environmental conditions allow the use of AdV as a reliable marker for detection of fecal contamination. In this work, the diversity of AdV along Belo Stream – in the city of Caxias do Sul, Rio Grande do Sul, Brazil – was evaluated. Samples were compared in both concentrated and unconcentrated forms. The identification of different AdV species was performed by amplifying a partial sequence of the DNA polymerase gene. AdV was detected in 24 out of 55 concentrated samples (43.6%) and the following species were identified: human adenovirus (HAdV) species C (4/55; 7.2%), D (6/55; 10.9%), E (2/55; 3.6%), and F (9/55; 16.3%). AdV related to other mammalian hosts, such as bovine adenovirus (1/55, 1.8%) and murine adenovirus (2/55, 3.6%), have also been identified; 23.6% (13/55) of the unconcentrated samples were positive, and identified as HAdV species C (6/55, 10.9%), D (1/55, 1.8%), and F (6/55, 10.9%). Results obtained evidenced the presence and the great diversity of AdV, mainly of human origin, circulating in Belo Stream. As expected, the concentration step performed helped to detect AdV in more samples.