Low Flow Estimation Using Hybrid Method in Northeast

Reliable estimations of low flow are extremely important for water management in arid and semiarid regions in drought periods. However, selecting reliable methods to determine low flows is difficult, and the lack of hydro-meteorological data as in the selection of a distribution for modeling purpose but also in the estimates of the parameters of a chosen model. In low flow estimation, the common approach for the mitigation of some of these problems is the regionalization of frequency. This study was carried out to evaluate the Hybrid method to estimate low flows in northeast of Iran and compare this method with Index Low-Flow method. At first, low flow series with duration of 7 days were chosen, then the best regional distribution function (Log Pearson Type III) was fitted and low flows value with different return periods were calculated. The region was divided into section based on the results of the cluster analysis, in the Index low flow, and based on area, in the Hybrid method. Then, related regionalized models were determined and compared using trial and error. The results showed that the Hybrid method enjoys higher degree of precision as compared to the Index low flow method, and regarding less error in data resources of the Hybrid method this method is recommended.