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    Experiences with previous versions of the Greenhouse Emission Model (GEM) for soilless cultures prompted the need for developing a revised version. GEM consists of a submodel for the water flows in the greenhouse (the WaterStreams Model, WSM) and a submodel for the pesticide behaviour in the greenhouse (the Substance Emission Model, SEM). The resulting emission fluxes are used by the TOXSWA model to simulate concentrations in surface water. This report describes the changes in WSM and provides a full description of the concepts and equations in the revised SEM version The main changes in WSM are the extension of options: (i) emission norms for nitrogen up to 2027 can be used, (ii) sodium levels can be set by the user, (iii) options for managing the discharge to the surface water are extended, (iv) a waiting time can be prescribed between a pesticide application and the next discharge. Option (ii) and (iv) are only available is used as a standalone model, i.e. outside GEM. There are two types of SEM: SEM-S for crops grown on slabs and SEM-P for crops grown in pots on tables. Main changes in SEM-S include: (i) the water in the slabs is divided into two equal parts with root uptake restricted to the first part, (ii) sorption to the slab material and the irrigation pipes is included, (iii) the amounts present in the air and condensation water immediately after spray or Low Volume Mister (LVM) application are strongly reduced, (iv) for spray and LVM applications direct contamination of the slabs, the drainage-water troughs, and the roof is added. Main changes in SEM-P include: (i) the amounts present in the air and condensation water immediately after an application are strongly reduced, (ii) the sorption equilibrium between the bottom 10 cm of the pots and the water on the tables was removed, (iii) for spray of LVM applications, the deposition on the tables is increased from about 10 to about 40%.

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    This technical report describes the concepts of the CASCADE_TOXSWA model as well as the technical implementation. CASCADE_TOXSWA is the landscape version of the TOXSWA model. TOXSWA is a so-called exposure model that simulates the fate of substances in surface water in single ponds, ditches and streams. The model is used in the authorization procedures for plant protection products in the Netherlands and in the EU. CASCADE refers to its use in simulating substance fate in and between the interconnected watercourses in a (sub-) catchment. The model has been developed to assess the fate of pesticides in an interconnected system of watercourses in a dynamic hydrological situation. CASCADE_TOXSWA can be used as a stand-alone version, but also as part of a landscape scale system model, to assess e.g. the effect of pesticide use on aquatic organisms. This report describes the concepts of CASCADE_TOXSWA with a focus on the functionalities added as compared to the single watercourse model TOXSWA.

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    The SedDis tool is a decision-support tool for selecting the optimal segmentation for the sediment in TOXSWA simulations. The TOXSWA model is used to calculate exposure concentrations of pesticides and their metabolites in watercourses and ponds. For the parameterization of the water body, its water layer and sediment layer need to be spatially discretized. For the sediment layer, the size of the grid (segmentation) is crucial. Selecting the optimal segmentation ensures that simulated concentrations are calculated with a satisfying accuracy when simulating the transport of strongly sorbing compounds within the TOXSWA model. The theoretical background and methodologyfor the SedDis tool is described. The procedure for using the SedDis tool is provided. Instructions for running the tool with an example (selecting standard or fine segmentation for a given scenario) are given.