Regional Frequency Analysis of Low Flow in Parts of the Northern Karun River Basin in Chaharmahal and Bakhtiari Province

Hydrological droughts reduce groundwater and surface water, lakes and rivers. The purpose of the present study was to analyze the minimum regional flow frequency in parts of the northern Karun basin in Chaharmahal and Bakhtiari province. For this purpose, 11 hydrometric stations were used. For the minimum flow estimation, 15 different physiographic, climatic and hydrological features of the basin were used in. At first, hydrometric stations were divided into two homogeneous groups using cluster analysis method. Then, using principal component analysis (PCA), the most important features were selected for each region among the 15 physiographic, climatic and hydrological characteristics. Finally, the models for estimating the minimum flow of each region were developed using stepwise regression method in return periods of 2, 10, 25 and 50 years. The results showed that the characteristics of the basin area with a weight of 0.347, elongation coefficient with a weight of 0.389, a length of the basin with a weight of 0.326 and a coefficient of roundness with a weight of 0.326 were the most important features in the estimation of minimum flow. In general, all regression-logarithmic models in the two regions for all rounds of returns with a coefficient of greater than 0.96 were considered to have a good performance for minimum flow estimation.