About SWAN

General Information

The ‘Surface Water Assessment eNabler’ (SWAN) is a software tool to assist in assessing application of exposure mitigation processes based on a FOCUS Surface Water Step 3 calculation. SWAN allows the user to incorporate mitigation measures for spray drift and run-off and account for dry deposition of pesticides, producing FOCUS Surface Water Step 4 exposure refinements as described in FOCUS landscape and mitigation and FOCUS air guidance. When doing this it uses the waterbody configuration as specified in the FOCUS surface water guidance. SWAN implemented runoff reductions following the FOCUS landscape and mitigation recommendations as described in section 3.5.2 Volume 1 of the FOCUS landscape and mitigation report. In particular those set out in Table 7 of this report section, are relied on for use in EU level assessments.

Note that SWAN also includes the option to apply mitigation implementing a mechanistic vegetative buffer filter strip model (VFSmod) that contains a topsoil texture as defined for each FOCUS runoff scenario.  VFSmod considers hydrological, sediment and chemical dynamics for each run-off event, where the most sensitive parameters for pesticide trapping Ksat und theta_s were selected by the model developers to result in an overall 10th percentile trapping efficiency for all soils covered by the respective R scenario. VFSmod runoff reduction results differ conceptually from the approach described in the FOCUS landscape and mitigation guidance.  As the uncertainty whether the  mitigation being modelled with VFSmod is achieved for all the other soil textures that the FOCUS scenarios cover still has to be independently evaluated, VFSmod  has not been accepted for use in EU level assessments and decision making.  VFSmod estimated runoff reductions may be accepted by some national competent authorities, in assessments supporting national product authorisations. Applicants are advised to confirm the situation with each competent authority.

The SWAN 5.0.1 tool is the intellectual property of CropLife Europe. The SWAN 5.0.1 development team is described on the SWAN splash and “About” screens that can be viewed following installation.  It should be noted that this was the situation when SWAN 5.0.1 was developed in 2018 and may be subject to change when subsequent versions are developed.

Questions and issues related to SWAN should be directed to the SWAN helpdesk at SWAN.Support@Syngenta.com



SWAN requires a completed FOCUS Surface Water Step 3 simulation (as calculated using FOCUS-SWASH) which acts as a foundation for application of mitigation.  Once a Step 3 run is loaded into the tool, the user can then select the mitigation options they wish to apply.  The current options are: spray drift, run-off and dry deposition (the selection of this is determined by the substance vapour pressure but can be over-ridden by the user).  The configuration of each option is made by the user on a separate screen for each one and typically gives a choice of selecting a buffer distance from which the mitigation is calculated by SWAN (e.g. in the case of spray drift, SWAN uses the FOCUS-Drift calculator to determine the drift loading for a given buffer), a drift reduction percentage consistent with spray drift reduction nozzles (e.g. 50%, 75%, 90%) or entering a user-defined loading for the mitigation option (e.g.  drift can be switched off if the user enters loadings of zero).  Once the mitigation options are configured, the user can then either run the Step 4 calculations immediately or save them for running later (a batch file is created to allow easy running).  The Step 4 calculations are run in the separate TOXSWA model and run outside of SWAN so there is no need to keep SWAN running whilst the calculations are performed.

SWAN has two modes of operation.  The user can either create a single step 4 calculation and run it or they can configure and run multiple Step 4 runs in “Batch mode” which will run unattended over a longer time frame (e.g. overnight).

It should be noted that SWAN is a tool that allows mitigation to be applied in a consistent manner in accordance with available guidance.  It does not manipulate existing Step 3 runs, but simply makes copies of the files it needs to operate to act as a foundation for Step 4 simulations.  SWAN does not apply mitigation in a way that cannot be done manually by the user; it is simply a user-friendly and efficient interface that avoids the need for complicated manual and error-prone file editing.


Download SWAN


Package                             SWAN_501.zip   (09/10/2021, 1 file 5.4 MB)

Test Results                        SWAN501Testing.zip   (09/10/2021, 1 file 1 MB)

Getting started

SWAN 5.0.1 was tested on 64-bit editions of Windows 7 and Windows 10.  32 bit operating systems should be compatible but have not been tested.  SWAN 5.0.1 is not compatible with Windows versions earlier than Windows 7.  Should you have a need to use SWAN on an earlier Windows version, you should contact the SWAN team (SWAN.Support@Syngenta.com) for advice.


In order to perform Step 4 calculations, SWAN requires that FOCUS-SWASH and at least FOCUS-TOXSWA are installed on the target system.  SWAN will install without checking whether these models are installed and it remains the user’s responsibility to ensure that the SWASH suite is correctly installed on the target machine.  If the user simply wants to view SWAN mitigation parameters from previously run Step 4 calculations, this is possible without the SWASH suite installed, but it will not be possible to make changes or run simulations without having SWASH installed.



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