Determination of the Best Hydrological Regional Homogeneity Method for Regional Flood Analysis in Western Drainage Basins of Iran

In this research، the hydrological homogeneity was used from three methods based on natural characteristics (Political boundaries of three provinces), characteristics and flow hydrological reaction (homogeneity Langbin test) and cluster analysis (Wards method) for regional flood analysis in basins located in three western provinces in Iran (Hamedan, Lorestan and Kermanshah). For this reason, firstly, necessary information and data were collected and secondly, periodical series of peak discharge were estimated during common statistical period (26 year) in 30 hydrometric selected stations. Using regional suitable distribution (log Pearson III type), peak discharges were estimated in different return periods. The research regions were divided into two homogenous areas in cluster analysis method, one homogenous area in Langbin test and three homogenous areas in political limits method. Then, discharge equations related to two- year return period was estimated in homogenous areas and all areas. The results demonstrate that obtained relations in homogenous regions using cluster analysis method have the least standard error and the greatest determination coefficient (R2). Therefore, cluster analysis was proposed as the best homogeneity method.