The influence of effective rainfall on modeled runoff hydrograph Influence of the pattern of effective rainfall on modeled hydrograph was investigated in the study. The modelling was performed with ...the U.S. Army Corps of Engineers hydrograph package HEC-HMS 3.2 and calibrated and validated on measured hydrographs of Glinscica watershed. Six different models of rainfall loss were applied and their effect on modeled hydrograph was evaluated. Peak discharge, time of peak discharge and runoff volume were compared. The best results with the lowest RMSE in the study was obtained with the SCS curve number loss method. Also synthetic hyetographs of different probability and duration were used. Three positions of the maximum rainfall intensity at 25, 50 and 75 % of the rainfall duration were applied. The results showed essential differences in simulated time to peak and also differences in peak discharge. The differences in time to peak increases considerably with the increasing of the rainfall duration. Finally, the results of constant intensity distribution of rainfall of different durations were compared with those obtained with typical rainfall distribution with the position of the maximum intensity at 50 %. Results showed considerable differences in peak discharge and time to peak by longer durations of the rainfall.
Common unitgraphs obtained from streamflow data for a set of runoff events have higher peaks, shorter times to peak and generally shorter total durations than average unitgraphs obtained by ...conventional techniques from rainfall and streamflow data for single events. The calculated inputs to these unitgraphs lag behind the corresponding peaks in the catchment rainfall and continue after the end of rainfall. It eventuates that these inputs are best modelled by including a strongly non‐linear storage in the rainfall loss model. For common loss and storage parameters, runoff hydrographs from the overall model fit the observed hydrographs over a wider range of flows than predictions from application of conventional unitgraph methods. The new approach can be interpreted physically as a non‐linear process of rainfall loss and routing to stream channels, followed by linear routing of stream flow; or functionally as a separation of the common linear elements in the overall rainfall–runoff process from the loss and non‐linear elements. It has the potential to lead to improved predictions of storm runoff hydrographs.
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