Bank filtration models for PFAS infiltration into groundwater in Vienna and Budapest
This record contains a bank filtration and groundwater transport model for modelling PFAS infiltration into the bank filtered waters at one location in Vienna and two locations in Budapest; Tahi and Surany.
Description of the models
The bank filtration models are 3D physically-distributed transport models, modelled with MODFLOW 2005 and MT3DMS (physically-based models for flow and transport, respectively), implemented in iMOD-WQ (iMOD Water Quality) (Zheng & Wang 1999, Harbaugh 2005, Vermeulen et al. 2021, Vermeulen & Roelofsen, 2023). MT3DMS reads the flow field as calculated by MODFLOW and calculates the reactive PFAS transport along this flow field, which allows for transient simulation.
For employing both the 1D and 3D transport modelling approaches, a regional groundwater flow model of the entire Danube island of Szentendre in Budapest was constructed using MODFLOW 2005. This model was employed as 3D MODFLOW model consisting of 6 model layers of variable thickness with a horizontal cell size resolution of 50x50 m. The regional groundwater flow model was calibrated against head measurements in the pumping wells on the island for a monitoring period (measurements conducted between 2022-2024). This regional groundwater flow model provides the data basis as well as the boundary conditions for the two local cut-out models located at the monitored sites in Budapest (Surany and Tahi), which were further calibrated on water levels in the monitoring wells at both sites. Like their parent model, both of these models have 6 layers, but have a higher resolution of 5x5 m. The higher resolution allowed all of present pumping wells within the two Budapest domains to be modelled in more detail, including a vertical shaft and five horizontal adits of 15-35 m length, arranged in a star shape. The Vienna model was constructed without a separate regional model, contains no pumping wells and has a resolution of 4x4 m.
The three models are used to study reactive PFAS transport during the bank filtration process using the RCT package within iMOD-WQ, which allows for one-site nonequilibrium sorption. A daily time-step was implemented for the groundwater flow model. For the monitoring period, normally distributed daily PFAS concentrations in the Danube river were generated on the basis of statistical data from the measurements at the respective sites (minimum, mean, standard deviation, maximum) using the Python-command np.random.normal (Harris et al., 2020). Besides the monitoring period, various scenarios can be modelled, namely a reference scenario, a baseline (BL) scenario, an accidental spill (AC) scenario with old firefighting foam (AC1) and one with more modern firefighting foam (AC2), and a water pollution control (WPC) scenario, based on limited measures (WPC1) as well as far-reaching control measures (WPC2). All scenarios can be run for a pre-climate change situation (based on the hydrological year of 2013), as well as for a post-climate change situation (based on the hydrological year of 2018). More information on the scenarios can be found in chapter 4.6.3 and 4.6.4 of the Guidance Document of H2020 Project PROMISCES, available at the project’s website (https://promisces.eu/) from June 2025 onward.
iMOD-WQ was developed by Deltares in 2012 as a way of combining the then-existing iMOD environment with additional MODFLOW packages such as MT3DMS, RT3D and SEAWAT. The advantage of this is that everything can be run within the iMOD-environment, using iMOD-formatting (e.g. IDF- and IPF-files) for input and output. It allows for SEAWAT calculations, including reactive transport, on top of MT3DMS waterflux simulations. Furthermore, parallel simulations can be carried out with the Parallel Krylov Package (PKS) to reduce calculation times (Verkaik et al. 2015).
Here, the bank filtration models are provided as a zip file. After unzipping, the models can be run by using the iMOD Graphical User Interface (GUI) or by using the iMOD Python package (freely available at https://gitlab.com/deltares/imod/imod-python, documentation at https://deltares.github.io/imod-python/). With the latter, one is able to make quick changes to the models (e.g. changes to hydraulic conductivities, pumping rates, etc.) by editing the runfiles directly. The input files for the models are already structured correctly for use with the iMOD Python package (see below). After the installation of iMOD-python, the models can be run by executing „run.bat“, and the scenario can be chosen by changing the runfile within „run.bat“ (see also the readme file in the main folder).
The output of the models consists of IDF-files with water levels and concentrations of each species of PFAS, for each layer at every timestep (i.e. daily). These can be read out either with the iMOD GUI or programming software like Python. Because the models are computationally taxing (especially on the CPU), a strong computer is advised.More information on how to use iMOD-WQ and iMOD-python can be found in the manual: https://content.oss.deltares.nl/imod/imod56/iMOD_User_Manual_V5_6.pdf
Licensing:
The GPLv2 license is meant for the software that is present in this record, the CC BY 4.0 license for the data.
