A simple lumped mass-damper idealization of impounded reservoir water is suggested in this paper. The effect of impounded reservoir water was modeled as virtual lumped mass which simulates the hydrodynamic pressure according to Westergaard (1933), but the lumped mass approach does not consider the surface wave generation and wave transmission through the boundaries. On the other hand, acoustic/ water elements can be employed to model the dam-reservoir interaction which can capture the above mentioned effect, but that needs more computational effort and expertise. In this paper, equivalent dampers together with the virtual mass are lumped at the upstream face to simulate the effect of the impounded reservoir water on the dam. A simplified procedure is proposed for calculating the coefficient of dampers using the geometry of the reservoir and impedance of the foundation and dam materials. A comparison of response of lumped mass-damper model with acoustic water model is also presented.