DROPLET is the acronym for “DRinkwater uit OPpervlaktewater Landbouwkundig gebruik Evaluatie Tool”. For the nine Dutch surface water abstraction points for drinking water production it calculates the expected pesticide concentration after Good Agricultural Practice. DROPLET uses the edge-of-field concentration in the FOCUS D3 ditch as a starting point for its calculation (with spray drift deposition according to the Dutch Drift Table and not the FOCUS Drift Calculator).
Next, pesticides flow from the edge-of-field ditch to the abstraction points situated in larger water bodies downstream. On their way towards the abstraction points, the concentration is reduced by pesticide dissipation processes and inflow from water not containing pesticides.
The following factors are taken into account:
- all crops on which the pesticide may be used
- the ratio of the relevant crop area and the entire intake area
- the market share of the pesticide
- the difference in timing of applications
- a factor correcting the implicit dilution of peaks caused by drainage entries due to the layout of the FOCUS ditch scenario
- a factor indicating the fraction of treated area contributing to the peak differentiated for spray drift and drainage
- degradation and volatilization
- in some cases additional dilution by a lake or incoming river
Scheme demonstrating the use of DROPLET in the tiered assessment procedure applied in the registration procedure in The Netherlands.
