3. Materials and methods
The sampling stations were chosen along the Thur River and its main tributaries the Murg (M), the Necker (N) and the Sitter (S). The sampling stations were chosen at the headwaters of the Thur River and at its lower reach (T1)–T(E) and along its tributaries (S1–S3 along Sitter, N1–N3 along Necker, M1–M3 along Murg) (Fig. 1). The impact of the tributaries on the Thur River hydrochemistry was better analyzed by choosing sampling stations along the main river both up- and down-gradient from each tributary