Abstract. The wflow_sbm hydrologic model, recently released by Deltares, as part of the Wflow.jl (v0.6.1) modelling framework is being used to better understand and potentially address multiple operational and water resources planning challenges from catchment scale, national scale to continental and global scale. Wflow.jl is a free and open-source distributed hydrologic modelling framework written in the Julia programming language. The development of wflow_sbm, the model structure, equations and functionalitities are described in detail, including example applications of wflow_sbm. The wflow_sbm model aims to strike a balance between low-resolution, low-complexity and high-resolution, high-complexity hydrologic models. Most wflow_sbm parameters are based on physical characteristics or processes and at the same time wflow_sbm has a runtime performance well suited for large-scale high-resolution model applications. Wflow_sbm models can be set a priori for any catchment with the Python tool HydroMT-Wflow based on globally available datasets and through the use of point-scale (pedo)transfer functions and suitable upscaling rules and generally results in a satisfactory (0.4 ≥ Kling-Gupta Efficiency (KGE) < 0.7) to good (KGE ≥ 0.7) performance a-priori (without further tuning). Wflow_sbm includes relevant hydrologic processes as glacier and snow processes, evapotranspiration processes, unsaturated zone dynamics, (shallow) groundwater and surface flow routing including lakes and reservoirs. Further planned developments include improvements on the computational efficiency and flexibility of the routing scheme, implementation of a water demand and allocation module for water resources modelling, the addition of a deep groundwater concept and distributed computing with a focus on multi-node parallelism.

Many impact assessment studies rely on hydrological and hydrodynamic (hydro) models. These models typically require a large set of parameters derived from different datasets and hence manual setup can be time consuming and hard to reproduce. HydroMT (Hydro Model Tools) is an open-source Python package that aims to make the process of building model instances and analyzing model results automated and reproducible. The package provides a common interface to data and model instances, workflows to transform data into models based on (hydrological) GIS and statistical methods, and various methods to analyze model results. The user can describe a full model instance including its forcing in a single configuration file based on a sequence of workflows, making the process reproducible, fast, and modular. The package has been designed with an iterative, data-centered modeling process in mind. First-order model schematizations can be built for any location in the world by leveraging open global datasets. These can later be improved by updating the input datasets with detailed local datasets. This iterative process enables the user to quickly get an initial result to then make informed decisions about the most relevant improvements and/or required data collection and to kick-start discussions with stakeholders. Furthermore, model parameter maps or forcing data can easily be modified for sensitivity analysis or calibration to support these robust modeling practices. HydroMT is successfully being used for several model software through a plugin infrastructure that allow for model specific functionality, such as readers and writers of model data formats, and can easily be extended to new model software. Currently supported model software include the distributed rainfall-runoff model Wflow, the hydrodynamic flood model SFINCS, the water quality models D-Water Quality and D-Emissions and the flood impact model Delft-FIAT.