Analyzing the frequency of non-stationary hydrological series based on a modified reservoir index

Abstract

Human activities and climatic changes have caused severe changes in hydrological values in recent decade. On the other hand, extreme values such as those of flood have non-stationary properties and using its data for hydrological studies requires stationary properties, while most meteorological variables have stationary properties. Some dams established in the Lake Urmia Basin (LUB) have provided an opportunity to control all hydrological variable of catchment area. In this study, extreme values were simulated and confirmed in an annual scale for hydrometric stations constructed after constructing the reservoir using modified reservoir index (MRI) in Zarinehrood basin in south of Lake Urmia. Results obtained from evaluating trend of studied values expressed that the Nezamabad (NA) hydrometric station is influenced by Shahid Kazemi and Norouzlo reservoirs among stations in the Zarinehrood basin. MRI was used to rebuild studied data. Statistical tests were used to evaluate accuracy of the method. Results of correlation coefficient between maximum flow discharge data of NA hydrometric station and upstream station showed a 53% correlation. Also, results obtained for trend of rebuild series indicated that there is no significant trend in time series. Results also showed that the two sets of time series distribute the same statistics by evaluating statistical distribution fit on rebuild maximumflow discharge and maximumflow discharge of upstream station. Results obtained from measuringMRI demonstrated high efficiency of this method in producing maximum flow discharge for stations constructed after construction of the dam.