Optical methods such as turbidimetry, UV-visible spectroscopy and fluorescence spectroscopy are alternative methods for water quality characterization. They are reagent free and can be used in-situ or off-line. These methods have been used to assess and compare the quality of various streams in the Moselle watershed. Moselle (550 km) is a major tributary of the Rhine river and is flowing through three Western European countries (France, Luxembourg and Germany). The streams have been selected with respect to the human activities these sub-watersheds sustain: forestry, agriculture, industry (paper mills, textile, steel mills, salt), urban centers. The comparison is first made directly on the spectra (fluorescence, UV-visible). In a second step Principal Components Analysis is applied.