Surface water is an important source of drinking water in many European countries. The concentration of plant protection products (PPP) at drinking water abstraction points is hence of interest and also a particular point in the EU regulatory framework (regulation 1107/2009). There is no EU-wide generic guidance available to derive predicted environmental concentrations (PECs) in abstracted water. The Netherlands employ a simplistic but reasonable first Tier approach as Edge-of-field PEC in surface water is diluted based on the use intensity (most important is the cropping area within a catchment) and other dilution factors like application practice and dissipation in the water system. However, the calculation of the dilution factor mostly considers highly simplified, worst-case assumptions. The Dutch approach assumes, e.g. that all agricultural land is connected and releases water to a single water body. Our work explored more realistic scenarios. Specifically, our goals were: (i) the derivation of more realistic dilution factors on landscape level; (ii) identification of representative vulnerable drinking water catchments in the EU for generic and regulatory use.  We analyzed different catchments in Europe using a combined approach of GIS analysis and landscape level modelling. In the first step, GIS was used to examine catchment characteristics (e.g., cropped area, crop type, and soil hydraulic properties) which have a strong impact on runoff generation. Second, the dilution for the most vulnerable catchment was modeled using the Soil and Water Assessment Tool (SWAT). This allowed us to explore the spatio-temporal controls of dilution in more detail. These insights regarding key factors can be used to derive representative vulnerable scenarios regarding the dilution on EU level for specific crop and PPPs. Our approach leads to crop-dependent dilution factors for typical catchments in the EU that potentially can be used as a tiered exposure assessment to derive a drinking water abstraction concentration.

Towards the derivation of realistic dilution factors for drinking water abstraction combining GIS analysis and landscape level modelling

2019 Fall National Meeting

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