Rainfall-Runoff Hydrologic Simulation Using Adjusted Satellite Rainfall Algorithms, a Case Study: Voshmgir Dam Basin. Golestan

In this study two satellite based rainfall estimates (TRMM and PERSIANN) were assessed to evaluate which rainfall product represents better the actual rainfall pattern and intensity of the basin. After evaluation based on statistical parameters such as the: Root Mean Square Error (RMSE), Mean Average Error (MAE), Mean Bias Error (MBE) and Correlation coefficient (R2), TRMM were selected for rainfall-runoff simulations. Among six years of available discharge data from 2002 to 2007, period of 2002 to 2004 was used for calibration whereas data from 2005-2007 were used for validation. In additional to continuous daily rainfall-runoff model development using HEC-HMS, an event based flood model was also developed. Also simulations based on daily TRMM versus 3-hourly TRMM were compared to evaluate effect of input time-step on the results. Results showed that the deficit constant loss method successfully predicted gauged catchment runoff and peak flows for the calibration (NSE= 0.413, R2=0.482, RVE= -0.246 %) and validation (NSE= 0.621, R2=0.670, RVE= -0.329 %) periods. Also developed model estimates monthly or longer time scale rainfall-runoff process better than daily scale. In addition, the event based HEC-HMS model developed using TRMM data with shorter time steps (3-hourly) showed good capability to simulate daily peak discharges. The study demonstrates the suitability of HEC-HMS for continuous runoff simulation in a complex watershed. Therefore, this work will have a significant contribution for the future development of water resources programs in this catchment in particular and in other data-scarce catchments.