Present work introduces the sustainable useful storage capacity as the minimum storage capacity able to satisfy the water demand for drinkable, industrial and irrigational purposes and necessary in order to overcome water deficit situations which, at least in Central Southern Italy, occur in the summer, when agricultural demand is really high. Sediment volumes to be removed from the reservoir bottom will be calculated as the difference between the current and the sustainable useful storage capacities of the reservoir in study. The calculation methodology of the useful sustainable storage capacity, based on the reservoir water balance between inflows at the reservoir and water demand, has been applied to the Camastra reservoir (Basilicata, Southern Italy), for which numerous reliable data including more than 40 years of inflows and water supplied volumes and data relative to 7 bathymetric surveys are available. Result analysis shows that this methodology, at least in the study case, enables sediment quantities to be removed more sustainably from a technical, economical and environmental point of view.