Reservoir Reliability as Affected by Climate Change and Strategies for Adaptation

Reservoir operational reliability indicates how satisfactorily the structure meets the water demand without failure. However, due to the stochastic nature of its operation, every combination of reservoir storage capacity and draft has an associated probability of failure (i.e., of having an empty reservoir). The objectives of this research were to design a method to assess reservoir reliability under present and future climate conditions, and to apply it to the Descoberto reservoir, with a capacity of 86 hm(3) and a design draft of 182.9 hm(3) yr(-1), located in central Brazil. The scenarios were the historic (1986-2005) and future RCM projection ensembles (2031-2050 and 2061-2080, RCP 4.5 and 8.5). Projected runoff was obtained with the Gardner model, and the reservoir budget was assessed by the concatenated behavior analysis (CBA). The reliability of the Descoberto reservoir, which was 100% during the historic period, was reduced to 15-50%, depending on the future climate scenario analyzed. The proposed adaptive measures, involving the reduction of reservoir draft and the increase in reservoir storage, were capable of maintaining a 100% reservoir reliability under the new climatic conditions, but with associated costs. The proposed method can be applied to other upstream reservoirs, providing water managers and stakeholders with a simple and robust reliability assessment and climate adaptation tool.