Pesticide transport from agriculture to surface waters:
Hydraulic shortcuts are a major transport pathway, but have been largely overlooked in the past
Pesticides used in agriculture are transported to surface waters through various pathways, impairing water quality and posing a major threat to aquatic ecosystems. Previous research suggests that so-called hydraulic shortcuts may be an important pesticide transport pathway. The term hydraulic shortcuts refers to inlet or maintenance shafts of agricultural storm drainage systems, but also to roads, farm tracks, channel drains, and ditches. Their relevance for pesticide transport in agricultural catchments has only been studied in single cases and it remained unclear how important hydraulic shortcuts are compared to other transport pathways. This project therefore aimed on systematically assessing the relevance of hydraulic shortcuts for the pollution of Swiss surface waters for the first time.
The results of the project show that hydraulic shortcuts are a major transport pathway of pesticides to Swiss surface waters, and that road storm drainage inlets are the most important shortcut type. Pesticides can be transported to surface waters by three main processes:
- Surface runoff via shortcuts (see Figure below): After a pesticide application, surface runoff formed on a crop area during a rain event is contaminated with pesticides. This surface runoff can flow into shortcuts and is then discharged to surface waters.
- Drift via shortcuts (see Figure below): During pesticide application, some of the spray liquid is deposited on non-target areas (e.g. nearby roads or farm tracks) by spray drift (i.e. transport via wind). During subsequent rain events, the deposited spray liquid can be washed off the non-target areas into shortcuts and is then discharged to surface waters.
- Improper handling: Due to improper pesticide handling (e.g. leaking spraying equipment, accidental spills, non-compliance with spraying buffers) spray liquid may be deposited on hard surfaces (e.g. roads or farm tracks). During subsequent rain events, the deposited spray liquid can be washed into shortcuts and is then discharged to surface waters.