Source of water pollution
Two main entry routes of plant protection products (PPP) into surface water need to be distinguished.
Point sources
Point sources are related to the handling of PPP mainly in the farmyard. Main risk areas are the cleaning; filling of sprayers and the management of contaminated diluted liquids resulting from cleaning and maintenance of sprayers on the farm.
Diffuse sources
Main diffuse source entry risks of PPP are related to field run-off and soil erosion due to adverse weather conditions (at or soon after the application), discharge from drainage systems (a specific form of run-off locally important) and from spray drift (off-target deposition of small droplets due to wind).
Most significant are entry risks from point sources followed by run-off/ erosion from fields.
Key differences in the mitigation of point and diffuse sources need to be con- sidered. Point source mitigation is farm-specific as it addresses operators’ behaviour directly and tries to optimise equipment and infrastructure to avoid mistakes. All relevant factors can be controlled.
Pollution from point sources therefore can be largely avoided.
Diffuse source mitigation is site-specific and depends also on uncontrollable factors like weather conditions and their interactions with soil and the shape of the landscape. It is linked to a water catchment area and individual fields. Mitiga- tion measures often need to be implemented on an individual level (single farmer, field scale) and at a collective level (group of farmers, catchment scale).
Diffuse source entries can be largely reduced but extreme weather con- ditions can cause, at least sometimes, entry risks beyond our mitigation capabilities.