The preservation of natural resources via the management of diffuse pollution is currently considered to be a significant challenge in France. Pollution reduction policies are notably based on the identification of vulnerable areas. In this context, our work aims to develop a method for characterizing the surface water vulnerability to phytosanitary pollution by implementing an interdisciplinary methodology combining geomatics, environmental science and agronomy. Such work consists in offering local stakeholders a decision support tool towards the participatory management of the diffuse pollution issue. This study is based on the geographic contribution of spatial analysis to the large-scale and high-definition identification of physical elements of the environment. It is also based on the study of agro-environmental indicators for the analysis of phytosanitary pressure on watercourses. The combination of these different data sources will make it possible to assess the vulnerability of diffuse pollution at a territorial level, by taking into account factors of agricultural pressure at plot level (crop types and phytosanitary practices), as well as factors of environmental sensitivity at watershed level (pedology, rainfall, topography, etc.). The results obtained will be mapped at plot level, then at the level of the Gimone watershed located in the southwest of France.