Uncertainties and errors flow estimate using hydrological modelling and precipitation by RADAR

Abstract This work presents an analysis of uncertainties and errors of the SCS-CN model of the Hydrologic Engineering Center - Hydrologic Modeling System (HEC-HMS), for hydrological events using observed and RADAR-estimated precipitation data of the São Miguel River Basin in State of Alagoas, which covers an area of 296 km². Physiographic data of the basin were used to find the initial estimates of the SCS-CN parameters. Then, using simultaneous measurements of precipitation and observed flow, the parameters were calibrated. Using independent data series, calibrated parameters were validated. The performance coefficient showed Nash-Sutcliffe values of 0.93 in the calibration phase and between 0.81 and 0.87 in the validation phase. The model was then used for past hydrological events, using RADAR-estimated precipitation data. This resulted in Nash-Sutcliffe coefficients between 0.75 and 0.79. The SCS-CN model with RADAR-estimated precipitation represented the time of the peak flow adequately; however, it underestimated the magnitude of the peak with errors up to 26% in some events. The methodology had satisfactory results for this basin and can be a useful tool for the prediction of flooding in other watersheds.