Nakayasu sentetik birim hidrograf metodunun Türkiye havzalarında kullanılabilirliğinin incelenmesi: Göksu Nehri Havzası örneği

The data obtained from unit hydrograph are being used to design of water structures like bridges, culverts, dams, irrigation channels etc. But when flow and precipitation data are incomplete or not available synthetic unit hydrographs are being used. The synthetic unit hydrograph methods commonly used in our country are Snyder, Mockus, DSİ synthetic methods. The synthetic unit hydrograph method which supposed by Dr. Nakayasu in 1940, is the method which will be examined in this study. Although this method has been commonly used in Far East country it is not being used in our country and European countries. In this study the usability of synthetic unit hydrograph supposed by Dr. Nakayasu in our country’s sub-basins is examined. Unit hydrograph data of Kayraktepe, Kirkyalan and Hamam which are in Goksu river sub-basins are used for modifying given equation of Nakayasu synthetic unit hydrograph methods. Given equations by Nakayasu are modified by using regression analysis and synthetic unit hydrographs of these sub-basins are obtained by using the new equations. The obtained unit hydrographs and observed average unit hydrographs are compared and Qp values for Kayraktepe sub-basin is calculated as 109,253 m3/s/mm, this value is calculated by a 0,769% error rate when compared to observed value of 110,1 m3/s/mm. The Qp values for Kirkyalan sub-basin is calculated as 37,909 m3/s/mm, this value is calculated by a 5,464% error rate when compared to observed value of 40.1 m3/s/mm and the Qp values for Hamam subbasin is calculated as 45,555 m3/s/mm, this value is calculated by a 9,244% error rate when compared to observed value of 41,7 m3/s/mm. The value of Tp is calculated for Kayraktepe as 28,037 hours, for Kirkyalan 22,476 hours, for Hamam 23,347 hours. The error rates of Tp values for these watersheds are respectively 0,132%, 2,164% and 2,721%. The value of Tg is calculated for Kayraktepe as 21,637 hours, for Kirkyalan 16,076 hours, for Hamam 16,947 hours. The error rates of Tg values for these sub-basins are respectively 0,171%, 3,051% and 3,710%. The value of Tb is calculated for Kayraktepe as 116,140 hours, for Kirkyalan 94,034 hours, for Hamam 97.847 hours. The error rates of Tb values for these sub-basins are respectively 0,121%, 1,384% and 2,153%. When these all results examined, the Qp, Tp, tg, T0.3, Tb parameters of unit hydrograph are calculated with very low error rates by using modified Nakayasu synthetic unit hydrograph method. As a result, we can say that these values are usable for Goksu River basin.