wflow is a distributed hydrological model platform that currently includes two models: the wflow_sbm model (derived from the topog_sbm soil concept) and the wflow_hbv model which is a distributed version of the HBV model. The models share the same structure but are fairly different with respect to the conceptualisation. The shared software framework includes the basic maps (dem, landuse, soil etc) and the hydrological routing via the kinematic wave. The Python class framework also exposes the models as an API and is based on the PCRaster/Python version 3.0 Beta.
The wflow_sbm model maximises the use of available spatial data. Soil depth, for example, is estimated from the DEM using a topographic wetness index. The model is derived from the CQFLOW model (Köhler et al., 2006) that has been applied in various countries, most notably in Central America. The wflow_hbv model is derived from the HBV-96 model but does not include the original routing functions, instead it uses the same kinematic wave routine as the wflow_sbm model. The models are programmed in a dynamic GIS language called PCRaster (van Deursen, 1995) available as a Python extension. As such, the structure of the model is transparent, can be changed by other modellers easily, and the system allows for rapid development. In order to run the model both PCRaster and Python 2.5 are needed.