Elaboration of a typological method for agricultural drainage ditches and their potential behaviour with regard to pesticides

Abstract

In order to reduce non-point source pollution in small rural watersheds, various actions have to be encouraged, from developing "good practices" at the field scale to the identification of "buffer zones" in the watershed. In the particular case of partially land-drained watersheds, the hydrographic network is most of the time quite dense and should play a great role in limiting the transfer of pollutants collected at the field scale ("in-stream processes"). The aim of this paper is to present a method to characterize the potential buffer role of ditches. This method is based on a typological approach and had been applied to a small rural subsurface-drained catchment in Western France (brook of Cétrais, Loire- Atlantique). The results obtained in this particular watershed show that the actual hydrographic network has a limited potential role in reducing pollution by pesticides.