This work aims at discussing the importance of estimating sediment volume in reservoir planning and operation. Currently, stage vs area vs volume curves have been updated for only a few reservoirs in Brazil. Therefore reservoir volumes measured by limnimeter are usually overestimated Thus, it is necessary to estimate accumulated sediment volume in reservoirs, by means of transport and deposition sediment models or reservoir bathymetry. This study introduces some of the models presently used in estimating reservoir siltation and demonstrates the need for more sediment information data in Brazil in order to allow the use of computational fluid dynamics models. During the feasibility study of the implementation of a reservoir, active volume reduction is also an important factor to be considered in studying the economic feasibility of the project. Finally, another goal of this paper is to encourage Brazilian hydrologists to consider siltation in reservoir planning and operation models