Inspection of factors that influence the hydrological drought (Case study: Lorestan watershed province)

For optimization management planning of the water resources، particular in vast watershed، recognition of the hydrological relationships to determine influential hydrological factors in the hydrologic drought is necessary. Drought is one of the natural factors which in recent decades damaged many areas and environments in not only in Iran but also in the world. This research investigates factors that influence the hydrological drought analysis in Lorestan watershed province. In this research، we first selected 25 stations of Lorestan province which were suitable in geographic transmittance status and area varieties. The physiographical data of considered stations were derived through the topographic maps. These data were analyzed by factor analysis for 15 measured variables in the considered stations by R-3-1-1 statistical software. The Results have showed that the factors of rainfall، area، drainage density، and areas with poor vegetation as main factors have stated 84. 684 percent of total variations in the total selected data. Then، four selected factors were classified in to two homogenous groups by the cluster analysis. In order to test the accuracy of the cluster analysis in the homogenous areas، discriminant analysis was performed. Based on the four main selected factors in two homogenous areas، we have derived a differentiating function. The differentiating function coefficients in the standard mode showed that in the formed function، average rainfall and area with weight factor of 0. 979 and 0. 877، respectively، were the most significant group differentiator variables. Finally the coefficient correlation values indicate that these two groups are distinct from each other.