Calibration and assessment of synthetic unit hydrograph construction methods in Ekbatan Dam watershed in Hamedan.
2007
Farhadi, A`li Asghar | Nazar Puya, Hadi | A`li Rezaei, Hossein | Mazaheri, Habib Ol-Lah | Ghiyasi, Najaf Qoli
Unit hydrograph synthesis presentation in 1932 by Sherman and later researches for several years , could made special situation in flood discharge calculation . The presentation of geomorphological unit hydrograph in 1979 by Rodriguez-Iturbe and Valdes and considering geomorphological condition of watershed in hydrological response , really was the progression in hydrology and opened the new field for researchers to investigate the different aspects of the process that yielded valuable numerous research among 30 years ago . Determining the accuracy of applying this new method , it is required that these relationships is tested in different climatic conditions and several watersheds to present the best method for flood hydrograph and discharge estimation . The research was carried out to calibrate the geomorphological unit hydrograph model in Yalphan watershed outlet with area equal to 16835 ha (Yalphan hydrometry station on Yalphan river as main tributary incoming to Ekbatan dam reservoir) and using information about rainfall-runoff events from 1987 to 2003 . 33 rainfall-runoff events with non snow effects was selected and their observed unit hydrograph extracted . Then required parameters were determined for different methods of synthethic unit hydrograph (SUH) construction methods such as Snyder , SCS , triangle and geomorphologial instantaneous unit hydrograph (GIUH) by observed rainfall-runoff events compare or by studying geomorphologial parameters of watershed from 1:25000 scale digital topographic maps . In later stage by using prepared parameters and coefficients , SUHs in different methods corresponding to observed events was extracted and compared with observed values by statistical methods . Our conclusions show that Snyder and SCS methods have had more agreement with observed values . GIUH extraction by Rosso method underestimate the peak discharge and overestimate the base time . Finally GIUH extraction by Rodriguez-Iturbe and Valdes method (triangle shape assumption) present better responses .
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