Comparison of raingauge and NEXRAD radar rainfall data for streamflow simulation for a southern Ontario catchment

The aim of this paper is to compare simulated flows using radar rainfall inputs with those obtained using raingauge rainfall. Both versions of simulated flows are also compared with the observed streamflow. The differences in rainfall volume and spatial variability of these datasets were evaluated for 10 storm events at hourly and daily time-scales using the Hydrologic Engineering Center's Hydrologic Modelling System (HEC-HMS). The model was run in event-mode using the SCS Curve Number method and the Green and Ampt Infiltration method for a catchment in southern Ontario, Canada. For most of the events, the runoff hydrographs obtained using raingauge rainfall had better correlation with observed flows than those obtained using radar rainfall, or merged rainfall inputs. However, the merged rainfall gave better runoff simulations than those obtained using only-radar rainfall data. The use of "only" radar rainfall for hydrological modelling resulted in erroneous outputs. Therefore, adjustment of radar rainfall is important prior to its use for runoff simulations. The estimation of antecedent catchment conditions played a dominant role in the event simulations; therefore, the initial parameters should be carefully selected and calibrated. The SCS Curve Number option gave relatively better results in terms of runoff amount, peak flow-rate, and time to peak, than those obtained using the Green-Ampt Infiltration option.