Reservoir attenuation of floods from ungauged basins

In a typical reservoir routing problem, the givens are the inflow hydrograp h and reservoir characteristic functions. Flood attenuation investigations can be easily accomplished using a hydrological or hydraulic routing of the inflow hydrograph to obtain the reservoir outflow hydrograph, unless the i nflow hydrograph is unavailable. Although attempts for runoff simulation ha ve been made in ungauged basins, there is only a limited degree of success in special cases. Those approaches are, in general, not suitable for basins with a reservoir. The objective of this study is to propose a procedure fo r flood attenuation estimation in ungauged reservoir basins. In this study, a kinematic-wave based geomorphic IUH model was adopted. The reservoir inf low hydrograph was generated through convolution integration using the rain fall excess and basin geomorphic information. Consequently, a fourth-order Runge-Kutta method was used to route the inflow hydrograph to obtain the re servoir outflow hydrograph without the aid of recorded flow data. Flood att enuation was estimated through the analysis of the inflow and outflow hydro graphs of the reservoir. An ungauged reservoir basin in southern Taiwan is presented as an example to show the applicability of the proposed analytica l procedure. The analytical results provide valuable information for downst ream flood control work for different return periods.