Efficiency of Flow-Duration Curves Method for Verifi cation of a Hydrological Model (Case Study: Zola-Chay Watershed)

The flow-duration curve, has a great importance in design of dams, hydroelectric powers plants, watershed operations, drought risk assessment and checking the river ecosystems health, so it is better to be employed in the rivers hydrological plans. The aim of this study is to evaluate the efficiency of flow duration curves for verification of the Soil Moisture Accounting (SMA) model, in different time scales such as annual, semi-annual, seasonal and monthly modes to determine the effect of soil moisture on runoff generation in the Zola-Chay watershed. In this study, after the Zola-Chay watershed geometrical modeling using HEC-GeoHMS, soil moisture accounting model parameters were estimated and then rainfall-runoff simulation was done in different time scales. By examining flow-duration curves in different time scales with SMA model, it could be concluded that the flow-duration curves in the monthly time scale, were more accurate than the annual, semi-annual and seasonal time scales. These results endorsed the more accurate performance of monthly time scale compared with other time scales in rainfall–runoff simulation.