Rainfall-runoff modelling is a first stage of the simulation that creates the runoff time series for the individual catchments. The simulation of the flow in the river branches is performed at a second stage.
· There are several rainfall-runoff models available:
· NAM. A lumped, conceptual rainfall-runoff model, simulating the overland flow, interflow, and baseflow components as a function of the moisture contents in four storages.
· UHM. The Unit Hydrograph Model includes different loss models (constant, proportional) and the SCS method for estimating storm runoff.
· Time-area. A conceptual model where the runoff amount is controlled by an initial and a continuous hydrological losses, and where the shape of the hydrograph is controlled by a concentration time and a time-area curve.
· Kinematic wave. A non-linear model based on the kinematic wave approach. The surface runoff is computed as flow in an open channel describing the catchment, whereas infiltration is calculated using a modified Horton equation.