This work appears as part of implementation of the water quality and environment survey through the study of aquatic macrophytes of the natural reserve of the "Marais de Bruges" (Gironde). Aquatic vegetation sampling and morphometric parameter survey concerning 50-meter long sectors was done, in summer 1998, in the whole river network. Data from ditches were submitted to a typologie analyse, using the STATlab software. It shows that 15 kinds of ditches are identified, 8 of them can be considered as major. This typology has to be confirmed by other sampling in order to chose stations more representative for the survey. The macrophyte index calculation seems to confirm the hypothesis expressed in previous studies, that the reserve would play a role in water treatment, especially in stagnant ditches in which flouting vegetation is not dense.