Time Base as an Invertible Function of the Parameters of Gamma Unit Hydrograph

Abstract

Analytical but approximate invertible equations for time base of gamma unit hydrographs or unit kernel hydrograph (UKH), which are applicable to all catchments, are derived in terms of the parameters of the unit hydrograph. The time base has been linked to the time to peak and lag time for the gamma UKH. The gamma UKH is redefined taking the time base and time to peak as parameters, as these parameters are physically more conceivable than the conventional parameters. The widely used National Resource Conservation Service empirical equations for the time base are found not applicable to all catchments. The proposed equations can also be used for determining the conventional parameters from the known values of the time base and time to peak or lag time. Using the proposed equations for time to peak and time base, the gamma UKH is fitted to few published storm events considering the time base as a parameter.