Non-point pollution in watersheds in western France: what data should be collected for diagnosis?

Abstract

To trace non point source agricultural pollution on a watershed, one needs to analyse the impact of the watershed's physical characteristics, of the diversity of agricultural practices and of their spatial and temporal interactions. Because these phenomena are very complex, many teams are involved in developing models to better understand occuring processes. But on a real watershed it is not possible to continuously measure all the parameters that are required for these models: a very important question is to measure and survey the less bad information. The description of this information is the aim of this paper: the possible surveys, depending on the scale, the problems and the diagnosis methods are first described. Then some methods of data acquisition for soils, crops and agricultural practices are compared. These descriptions are illustrated by examples on some watersheds surveyed by our team.