Effects of an outflow regime adoption of the Sao Francisco River reservoir system to meet water demands for multiple uses

The establishment of reservoir operation rules is a strategy used to increase storage volumes and satisfy water demands. However, these rules are not always compatible with the flow regime required to meet environmental needs. This paper aims to evaluate the effects of an outflow regime adopted by the Sao Francisco River reservoir system, which includes environmental water requirements, in the current laws for meeting water demands for multiple uses, according to Resolution 2081/2017 of Agencia Nacional de Aguas - ANA. The methodology adopted was the construction and simulation of alternative outflow operation scenarios, for a regular and a dry hydrological period, which were the following: 1) Outflow scenario according to Resolution 2081/17 and (2) Outflow scenario that considers a proposed environmental flow hydrogram for the low course of the Sao Francisco river. The operation effects in the meeting of multiple water uses were quantified in each scenario and compared with each other. The results suggest that when the maintenance of the aquatic ecosystems is a priority, the system demonstrated low water security in meeting the reservoirs target volumes and satisfying water demands, including the environmental flows.