An extended hybrid model for synthetic unit hydrograph derivation

SummaryThe hybrid model (HM) is extended for the derivation of synthetic unit hydrographs by introducing the concept of translation, which is essential for describing the behavior of the dynamic system. A generalized form of the extended hybrid model (EHM) is also presented in the present study. Further synthesis of the generalized form of the EHM shows that the Nash and hybrid models are the special cases of the EHM. The workability of EHM and HM, with two serially connected units is compared with Nash model on five catchments ranging from 21 km2 to 452.25 km2. The study reveals that the extended hybrid model works significantly better than the hybrid model for large catchments and vice versa. The study also reveals that the Nash model performs poorer than both the models in all the cases. A sensitivity analysis of the proposed model reveals that the peak discharge (Qp) is more sensitive to both storage coefficients K1 and K2 than translation time T for both small as well as large catchments.