Hydrological homogeneity of basins

In the method of regional flood frequency analysis one of the main actions is grouping of homogeneous watersheds. The main target of this paper is to survey the circumstances of determining hydrologic homogeneous watersheds based on analysis of factors of physiography، climate and distribution parameters of annual peak flows include coefficient of variation، skewness and kurtosis. For investigate the consequences of homogeneity of basins and selection of effective variables to explanation of it، totally 16 sub basins with 30 years data series or longer have been selected in the Sefidrood Dam’s basin. After the physiography specifications of them measured and so by use of dominant probability distribution of region، the quantile flood of related hydrometry stations with different return periods estimated. Then by Ward’s clustering method، the conventional and L-moments of peak flows data in hydrometry stations and so based on physiography specifications of sub basins some clusters recognized and completely separated by canonical discriminate function. In continuing by use of physiography specifications and method of factorial analysis، the effective factors to peak flow defined and by fitting of multyvariations linear regressions the R2 of every of them have been computed. The results show that to many hydrological homogeneous basins that grouped based on distribution parameters the R2 in %1 level is significant but based on physiography specifications there is not significant. The conclusion is that recognizing the homogeneity of basins have to be done based on the moments of is not hydrometry stations.