Análise de riscos do atendimento das demandas hídricas do sistema de reservatórios Poções – Epitácio Pessoa.

Abstract

Water scarcity is one of the major challenges facing water resources management in the semiarid region of northeastern Brazil. This study aimed to analyze the risks associated with meeting water demands within the Poções – Epitácio Pessoa surface reservoir system, considering different levels of external inflow from the East Axis of the São Francisco River Integration Project (PISF). The methodology is based on a stochastic and probabilistic approach, using a 32-year historical precipitation record as the reference for generating 1,000 synthetic series through a truncated Normal distribution. Precipitation data were converted into reservoir inflows using the SMAP hydrological model and subsequently used to simulate the operation of the reservoir system in AcquaNet over a five-year operational horizon. Eleven scenarios were established, representing inflows ranging from 0 to 100% of the 4.2 m³/s discharge allocated by the PISF. For each scenario, reliability and vulnerability indicators were calculated and subsequently converted into levels of failure probability and impact according to a methodology adapted from the Tribunal de Contas da União (TCU), allowing the results to be classified into low, medium, high, and extreme risk categories. The results showed that, in the reservoirs along the receiving axis – Poções, Camalaú and Epitácio Pessoa – increasing external inflow progressively reduced the occurrence of higher-risk classes, although the response varied among reservoirs and water-use categories. Public water supply showed a greater response to external inflow because of its operational priority, whereas other uses required larger shares of the transferred flow to reach lower-risk conditions. The Poções reservoir showed the greatest vulnerability and dependence on the PISF, while Camalaú exhibited a rapid public-supply response to external inflow, and Epitácio Pessoa demonstrated greater relative robustness. In the auxiliary reservoirs, risk levels remained unaffected by PISF inflows, with critical conditions particularly associated with other water uses in Sumé and Santo Antônio. It is concluded that the PISF is a strategic component of the system’s water security, however its effectiveness depends on the proper alignment of water availability, demands, allocation priorities, operating rules, and local hydrological characteristics.