Climate change could affect water resources and hydraulic infrastructures seriously. Dimensioning and operation of reservoirs should therefore be modified according to climatic change scenarios. To assess the effect of climate uncertainty on reservoir volumes dimensioning using cost-benefit analysis, a model of reservoir dimensioning at the river basin scale is applied in Greece. For the case study, there is no cost of error and adaptation seems to be inefficient. A methodology at the scale of the Mediterranean region with a generic modeling at the river basin level is developed. Reservoirs networks and reservoirs-demands links are reconstructed and coordinated reservoirs networks operation is determined, using only globally available data. The link reconstruction methodology is applied on irrigation demand and validated qualitatively on Algeria. Change in reliability with adaptation of reservoir operating rules under climate change over the Mediterranean region is then assessed. Reliability changes seem to be more influenced by inflow changes than by demand changes. They are not important for the Nile basin and the European and Middle East sub-regions, while in North African countries with a more pronounced Mediterranean influence, like Tunisia or Algeria, reliability decrease can be significant
