Development of a Geomorphological Unit Hydrograph of Reservoir and Comparison with Nash's Unit Hydrograph (Case Study: Kamanaj- Bala catchment)

In order to optimum use of dam’s reservoirs, and regulation of the river and flood alert, forecasting of rivers discharge is of great importance. Rainfall- runoff is one of the complex hydrological process that depends on many factors, such as soil moisture, land use, geomorphology, evaporation and infiltration of catchments. In this research, the unit hydrographs resulted from geomorphological unit hydrograph of reservoir (GUHR) and Nash models for the Kamanaj bala catchment flood discharges, the catchment which located in Eastern Azarbaijan, were compared with the observed unit hydrographs. The criteria used for evaluation of the models include: coefficient of determination (R2), error in volume of hydrograph (V%), error in peak flow (QP%) and error in time to peak (TP%). According to the results both methods simulated peak flows smaller than those of observed. Nash model predicted time to peak earlier than the observed one, while GUHR model predicted it later. But generally GUHR model simulated peak flow and time to peak better than Nash model. The sensivity analysis of models carried out based on their parameters variation. Results showed that the hydrographs indicated high sensitivity to their parameters of related models.