Geomorphological instantaneous unit hydrograph model with distributed rainfall

Two variants of the Instantaneous Unit Hydrograph model based on a Geomorphological association of linear Reservoirs (IUHGR), incorporating the Spatial Variability of Rainfall (SVR), have been developed. The proposed models are based on the Geomorphological Reservoirs (GR) scheme consisting of a cascade of linear reservoirs aggregating sub-watersheds. The model, in its first version, was formulated so that it incorporated a spatial variability pattern of rainfall associated with a certain frequency and oriented towards its application in the field of hydrological design. This model was considered to be stationary in the time (GRSVR(s)) for being linked to some design conditions. The second version of the model is applicable to the simulation of real events, where there is a dynamic (GRSVR(m)) spatial distribution of rainfall that varies in time, as in the case of the movement of rainstorms. Both models permit the input of relevant information on the spatial variability of the rainfall, taken from different rain gauge records, without losing the simplicity of the GR model with a single parameter, which represents the hydrological time response of the watershed. The models have been calibrated and validated with the data from one gauged watershed in northern Spain. The analysis conducted in both cases showed that the models which contemplated the spatial variability of the rainfall, GRSVR(s) and GRSVR(m), were capable of simulating rainfall variability effects in the surface runoff hydrograph better than the GR model, which averages the precipitation values recorded in the different rain gauges.