DROPLET to calculate concentrations at drinking water abstraction points : user manual for evaluation of agricultural use of plant protection products for drinking water production from surface waters in the Netherlands

The user-friendly shell DROPLET, acronym for DRinkwater uit OPpervlaktewater- Landbouwkundig gebruik Evaluatie Tool, assists the Dutch Board for the Authorisation of Plant Protection Products and Biocides (Ctgb) in evaluating whether pesticides may exceed the 0.1 μg/L standard in one of the Dutch surface water abstraction points for drinking water production. It operationalises the methodology developed by a Dutch expert group described in Adriaanse et al (2008). This manual explains how to use (i) SWASH to enter compound properties and application pattern, (ii) to run MACRO to calculate the drainage fluxes, (iii) to enter the deposition according to the Dutch Drift Table in TOXSWA, next (iv) to run TOXSWA to obtain an edge-of-field concentration in the FOCUS D3 ditch and finally (v) to run DROPLET to obtain the concentrations in the nine Dutch abstraction points plus the Bommelerwaard. DROPLET maintains a central database (in addition to the SWASH database) and combines the peak concentration of the FOCUS D3 ditch with intake area and compound specific factors, such as crop areas and compound degradation to calculate concentrations in the abstraction points.