In the French West Indies, high pest pressure on cropping systems has triggered high inputs of pesticides, especially in banana cropping systems. These pesticides then disperse in soil, ground and surface water, threatening ecosystem and human health. Reducing the environmental impact of banana cropping systems in this area requires i) predicting environmental states according to cropping systems evolution, ii) identifying key factors triggering pollution, and iii) proposing measures to reduce impact. Since farmers apply pesticides at the field scale while environmental impacts spring up at the watershed scale, multi-scale environmental impact assessments of pesticide use are required. Therefore, our work focuses on the characterization of i) pollutant input (type of molecule, quantity applied, frequency), ii) pollutant transfers, through hydrological modelling, and iii) environmental state through water quality measurements. Studies carried out at field scale, sub-watershed scale and watershed scale will be presented. They were located in Perou river catchment in Guadeloupe and Galion river catchment in Martinique. Results provide a wide overview of the main hydrological processes involved in pesticides transfers towards rivers in tropical volcanic catchments. However, those studies focused either on chlordecone, an old organochlorine, or cadusafos, a nematicide used 10 years ago in banana cropping systems. Recent measurements performed at the watershed scale showed herbicides applied in sugarcane fields and banana post-harvest fungicides to be among the main pollutants in these rivers. Consequently, long-term and multi-residue monitoring is required to understand the fate of the different molecules applied in fields taking account of cropping systems evolution over time. This will be further performed thanks to the set-up of the Observatory of agricultural-source pollution in the French West Indies (OPALE).