تخمين ثابت فروكش جريان پايه براي ايستگاه اهواز در رژيم طبيعي رودخانه كارون

Estimation of Baseflow Recession Constants for Karoun River in Ahwaz Station

Hydrograph recession constants are required for calibration of rainfall-runoff models, base flow augmentation studies, geohydrologic investigations and regional low flow studies. Low flow characteristics of rivers have been increasingly utilized in recent years as the demand for water has increased. In this study, five different estimators of the base flow recession constant are derived and tested for Karon river in Ahwas station. The integrated moving average method, IMA(0,1,0), because of predicting values within a constant limit is not suitable for this purpose. Also existing parameter AR(2) in second-order autoregressive model is not of much necessity, so first-order autoregressive model AR(1), is enough in time series model. Covariance method and solving watershed as linear reservoir method have offered eligible and very similar results but solving watershed as linear reservoir has limitation in use. In general, regression procedures for estimating hydrograph recession parameters are generally preferred to the time-series alternatives, and the result of covariance method is the most suitable model.