Derivation of Unit Hydrographs for Ungauged Catchments

Snyder based on a study of a large number of catchments in Appalachian Highlands of eastern United States developed a set of empirical equation for synthetic unit hydrograph in those areas. These empirical equations are of regional validity, which relates the salient hydrograph characteristics to the basin characteristics. For developing unit hydrograph of catchments detailed information about the rainfall and the resulting flood hydrographs are needed. But such information would be available only at few locations and that for remote locations would be normally very scanty. These empirical equations of regional validity will help in constructing the unit hydrograph for the particular region. In this paper attempt has been made to derive synthetic unit hydrograph for the Krishna Pennar river basin area in Maharashtra. The model which has been used for a statistical fitting on the data of the catchments within the sub zone is Y=CX^P. Knowing L, Lc and S of a catchments under study, the various parameters of the unit hydrograph such as t_r, t_p, t_m, Q_p, q_p, W₅₀, W₇₅, W_R50, W_R75, and t_b. can be determined for ungauged catchments located in the sub zone. The equations are derived to determine the various parameters of unit hydrograph.