Development of Conceptual Rainfall- Runoff Model for Quick and Slow Runoff Simulation (Case Study: Navrood Basin, Iran)

Although many kinds of rainfall-runoff models have been developed by hydrologists, the unit hydrograph methods are still gainful tool for flood estimation in many basins where recorded hydrological data are not sufficient to support distributed rainfall- runoff models. The aim of this paper is to derive the analytical unit pulse response functions of quick and slow runoff of stream flow using a conceptual model containing three serial tanks as well as a parallel hybrid tank. The interrelation of the tanks can be shown using exponentially structured models which their parameters reflect the physiographical characteristics of the basin. Parameters of the model were estimated using Nelder–Mead optimization method. Efficiency and validity of the developed conceptual model were evaluated for various observed events using statistical criteria such as Nash-Sutcliffe, mean relative absolute error for discharge, peak flow and runoff depth. Results showed that the developed model had good capability in predicting rainfall- runoff process considering soil moisture conditions before rainfall occurrence without the need for definition of excess rainfall.