University of Tehran Press Journal of Ecohydrology 2423-6098 2 2 2015 06 22 Efficiency Evaluation of Diskin Method in Derivation of Instantaneous Unit Hydrograph in Jafar-Abad watershed, Golestan Province Efficiency Evaluation of Diskin Method in Derivation of Instantaneous Unit Hydrograph in Jafar-Abad watershed, Golestan Province 141 150 56144 10.22059/ije.2015.56144 FA Raoof Mostafazadeh Assistant Professor, Dept. of Rangeland and Watershed Managemnet Abdolreza Bahremand Associate Professor, Dept. of Watershed Management, Gorgan University of Agriculture Sciences and Natural Resources, Gorgan, Iran Mohsen Zabihi PhD Student in Watershed Management Sciences and Engineering, of Science Graduated, Dept. of Watershed ‎Management Engineering, Faculty of Natural Resources, Tarbiat Modares University Journal Article 2015 07 13 Instantaneous Unit Hydrograph (IUH) is the response of a watershed subjected to a storm with an excess rainfall of ‎‎1 unit depth occurring on the watershed instantaneously, used as the response function in rainfall- runoff modeling. ‎Omission of excess rainfall duration from unit hydrograph theory has made it better and easier to investigate on ‎rainfall- runoff relationship. This study focuses on derivation of IUH from direct runoff hydrograph using Diskin ‎method in Jafar Abad watershed (109 km2) located in Golestan province. Using hourly hydro-meteoerological data ‎the index unit hydrograph was derived from 27 storms by S curve method and then index IUH was calculated from ‎S curve. Then the Diskin method was used for derivation of IUH from 4 different direct runoff hydrographs. The ‎efficiency of Diskin method was evaluated by statistical comparison with the observed IUH. The results indicated ‎that the method derived IUHs with good accuracy, 85% according to the Nash-Sutcliffe criterion. Also mean relative ‎error of instantaneous peak discharge and relative error of instantaneous time to peak, are 2.24% and 6.25% ‎respectively while the model bias for water balance is -0.92%. Nonetheless more researches in other watersheds are ‎suggested for derivation of instantaneous and flashy floods for planning into reduction of flood damages.‎ Instantaneous Unit Hydrograph (IUH) is the response of a watershed subjected to a storm with an excess rainfall of ‎‎1 unit depth occurring on the watershed instantaneously, used as the response function in rainfall- runoff modeling. ‎Omission of excess rainfall duration from unit hydrograph theory has made it better and easier to investigate on ‎rainfall- runoff relationship. This study focuses on derivation of IUH from direct runoff hydrograph using Diskin ‎method in Jafar Abad watershed (109 km2) located in Golestan province. Using hourly hydro-meteoerological data ‎the index unit hydrograph was derived from 27 storms by S curve method and then index IUH was calculated from ‎S curve. Then the Diskin method was used for derivation of IUH from 4 different direct runoff hydrographs. The ‎efficiency of Diskin method was evaluated by statistical comparison with the observed IUH. The results indicated ‎that the method derived IUHs with good accuracy, 85% according to the Nash-Sutcliffe criterion. Also mean relative ‎error of instantaneous peak discharge and relative error of instantaneous time to peak, are 2.24% and 6.25% ‎respectively while the model bias for water balance is -0.92%. Nonetheless more researches in other watersheds are ‎suggested for derivation of instantaneous and flashy floods for planning into reduction of flood damages.‎ https://ije.ut.ac.ir/article_56144_0bad9c6010add0b043f35682156d6851.pdf