A rainfall-runoff model calculates the water balance of a hydrological catchment area. The most important output is the runoff at the outlet of the catchment area in response to the precipitation in the catchment area. The simulation can be event-based or continuous. In Talsim-NG the rainfall-runoff module is integrated into the sub-basin system element. Basically, all relevant physical processes of water storage and movement within the catchment area can be modeled (evaporation, snow accumulation and melting, soil moisture, etc.). Different calculation approaches are implemented and allow, depending on the given problem and data situation, to choose from simple, strongly abstracted approaches (e.g. discharge coefficient method) up to complex physically based approaches (e.g. soil moisture simulation). A detailed description of the calculation approaches can be found directly on the page of the sub-basin system element.