تعيين ضريب هرشفيلد (k) با استفاده از روش همگرايي در حوضه هاي خواف و كال شور استان خراسان رضوي

Estimation of Hershfield coefficient for Khaf and Kalshour basins in Khorasan Razavi province

The probable maximum precipitation (PMP) is the maximum possible depth of precipitation, which could occurs in a region. The PMP has so many influences on designing of dam weirs and storage constructions and water distribution. Therefore, the storage constructions and water distribution must design like they can stand maximum flood without any impairment. The synoptical (convergence) and statistical analysis are two general methods for the PMP estimation. The statistical or Hershfield method is used when rainfall quantities are available and sufficient. There is wprth exactness in convergence method because of using more parameters for PMP estimation. In this paper, by using of Meteorology Organization research which has estimated PMP for Khaf and Khalshour basins by convergence method and concerning 24h PMP in rainguage stations basin, k; was estimated for whole of the area. The 24h PMP data were received from synoptic and climatology stations in Khorasan Razavi province. Then PMP was estimated by first and second Hershfield methods. The results show that there are many differences between them and the Hershfieldʹs second method estimates PMP close to the convergence estimations.